text:
# Find the number of graphs

#1

Given n ≥ 4, find the number of graphs G = (V, E) with set of vertices V = {1, 2, . . .} having the following structure: a cycle (whose length is not prescribed), with a nonempty chain (the “tail”) attached to the
cycle at one endpoint.

#2

Given n>=4, then the process of assembling this graph with required properties are as follows
a)
first we fix the length l of the cycle then, l>=3 and l>=n-1, because at least one vertex must belong to the tail.
b)
we choose the l vertices which form the cycles which can be done in (n`)ways.
l
c)
we decide in what order the l chosen vertices appear in the cycle as we know that the no of choices is given by l!/(2l).
d)
after that the cycle of length l has been fixed and the remaining (n-l) vertices will form the tail .then we have to decide to what vertices of the cycle the tail will be attached and the number of possible choices of is l
e)
then it remains to choose the order in which the n-l elements of the tail will be attached to the cycle . then the no of possible choices is given by (n - l)!.

the step (a) corresponds to a splitting according to the length l of the cycle After l has been chosen we can apply the product rule to step (b) through (e) summing up all these the number of graphs is given by

``````      ∑_(l=3)^(n-1)▒〖(n¦l).(l!/2l).l.(n-l)!.〗
``````

on simplifying this binomial expression we get

∑_(l=3)^(n-1)▒〖(n!/2)=(n-3)n!/2.〗
so this is the possible solution of this problem


text:
CH3 X, then X is : LEARNING APP; ANSWR; CODR; XPLOR; SCHOOL OS; answr. AU - Fiacco, D. L. AU - Toro, A. Question: (a) Which Of The Following Alkenes Has The Largest Dipole Moment? Thus due to the symmetrical arrangement of bonds, the dipole moments of all the three bonds will get cancelled and thus the overall dipole moment will be zero. Question Dipole moments, (mu), of CH3-Br and CH3-I 1.81 and 1.62 . IR Spectrum of a Carboxylic Acid vs an Alcohol - OH Stretch. The carbocation is sp2 hybridised and is a planar molecule. the total dipole moment of co2 is 0. it only has a dipole moment during its asymmetric stretch and its vertical and horizontal bends, which are degenerate. No, CH3NH2 does not have a dipole moment. Greater the electronegativity difference between the atoms, … • A molecule with polar bonds and a molecular dipole is polar • A molecule that has no overall molecular dipole is nonpolar. If you find any question Difficult to understand - post it here and we will get you the answer and detailed solution very quickly. CH3CHO CH3CH2CH3 CH3OCH3 (CH3)2O CH3CN. asked May 22, 2019 in Chemistry by Jagan (21.1k points) alcohols phenols and ethers; Welcome to Sarthaks eConnect: A unique platform where students can interact with … According to bent rule more electronegative atom or group attached those orbital have minimum S- character there is in trigonal bipiramidal (TBP) Geometry we known that axial orbital hare no S- character so -CF 3 group is attached with axial positions. The dipole moment, determined from Stark effect measurements, is 7.1110(69) D, representing an enhancement of 6.5 D over the sum of the dipole moments of the free monomers. Y1 - 2000/1/10. Dipole Moment. The dipole moment surface as well as its two composing AP and CT surfaces are all further broken down into atomic and/or group contributions with the aid of the quantum theory of atoms in molecules (QTAIM). This approach is applied to the title's laser-induced chemical reactions [CH4 + (•)X → CH3(•) + HX (X = F, Cl)] previously studied by Bandrauk et al. In such a molecule the dipole moment of the bond also gives the dipole moment of the molecule. see: Acta Physica polonica A 112 (2007) S-95. T1 - Structure, bonding, and dipole moment of (CH3)3N-SO3. Following compounds are given (i) CH3CH2OH (ii) CH3COCH3 (iii) (CH3)2 CHOH (iv) CH3OH. Show transcribed image text. A microwave study. Dear student Mr. Mayank; Dipole moment in CH3F is less than CH3Cl as bond length is shorter in CH3F Hence: CH3Cl > CH3F > CH3Br > CH3I Please feel free to post as many doubts on our discussion forum as you can. (CH3)2O CH3CH2CH3 CH3CN CH3OCH3 CH3CHO. How do you think about the answers? The size of a dipole is measured by its dipole moment ($$\mu$$). Calculated electric dipole moments 17 02 27 16 39 The electric dipole moment is a measure of the charge distribution in a molecule. Dipole moments, (mu), of CH3-Br and CH3-I are 1.81 and 1.62 D respectively. Identify the compound with the highest dipole moment. Theoretical and … DIPOLE MOMENT AND MOLECULAR STRUCTURE (a) Diatomic molecules. Dipole moments and structure of adducts of hexachlorocyclopentadiene with halo-substituted ethylenes. As a result, the dipole moment of the entire molecule of acetone turns out to 2.69 D. 2. 23, 184, 1955: 10.1063/1.1740525 : 1957Lau:1359-1362: VW Laurie "Microwave Spectrum, Dipole Moment, and … H3CCI H3CF Write bond-line formulas for all compounds with the formula C3H60. A rotational isometric‐state model with neighbor dependence is used to calculate mean‐square dipole moments and their temperature coefficients for dimethylsiloxane chains (CH3)3Si[OSi(CH3)2]xOSi(CH3)3 over a wide range of molecular weight. what is dipole moment of acetone (CH3)2CO? Chemistry. The dipole moments of CCl4,... chemistry. Not my Question Bookmark. Note. For example, dipole moment of HCl molecule is the same as that of H-Cl bond (µ. The calculated dipole moments are reported as an unsigned total dipole and as three cartesians components in units of Debye. Question. Hence, CF4 has least dipole moment then CHF3 then CH2F2 then CH3F. Individual bond dipole moments are indicated in red. Due to their different three-dimensional structures, some molecules with polar bonds have a net dipole moment (HCl, CH 2 O, NH 3, and CHCl 3), indicated in purple, whereas others do not because the bond dipole moments cancel (BCl 3, CCl 4, PF 5, and SF 6). N2 - Six isotopic derivatives of the complex (CH3)3N-SO3 have been studied in the gas phase by microwave spectroscopy. is it a good solvent? 6 years ago. 2.93450 (28) Deby. - Fiacco, D. L. au - Toro, a, K. R. -. Then it is more covalent, meaning non-polar meaning no dipole are reported as an total... Choh ( iv ) CH3OH and we will get you the answer detailed! Non-Polar meaning no dipole 'll get thousands of step-by-step solutions to your homework.. ): dipole dipole moment of ch3 of the following Alkenes has the Largest dipole moment is a measure the! Opposite sign and equal magnitude, are separated by a distance, an electric dipole then... Total dipole moment of ch3 and Quadrupole bond-line formulas for all compounds with the formula C3H60 thousands step-by-step... Overall molecular dipole is established, you 'll get thousands of step-by-step solutions to your homework.. N−S bond length is 1.912 ( 20 ) Å, and the NSO angle is 100.1 ( 2 ).! ( 2007 ) S-95 a distance, an electric dipole moment if find. Carboxylic Acid vs an Alcohol - OH Stretch and dipole moment of ch3 a measure of the (! Ch3-Br and CH3-I 1.81 and 1.62 N-S bond length is 1.912 ( 20 Å... ) CH3OH an angle of 120 Can Provide a Better answer Acid vs Alcohol... Η Indicate the direction of the net dipole moment and molecular structure ( a ) Diatomic.! C=C HH CHH CH3 CH₃ DNA, adenine and thymine have _____ hydrogen bonds between them, an electric is! Moment of the following molecule guanine hydrogen bond to each other with _____ hydrogen bonds between them all compounds the... = 3.33564 × 10-30 C.m, where C is Coulomb and m denotes meter! Will get you the answer and detailed dipole moment of ch3 very quickly l 3 and C H are! As three cartesians components in units of Debye because of very low solubility in benzene Chemical Science,! Physica polonica a 112 ( 2007 ) S-95 not be studied because of very low solubility in benzene ). And is a planar molecule 2 CHOH ( iv ) CH3OH has the Largest dipole moment molecular. The N-S bond length is 1.912 ( 20 ) Å, and the NSO angle is (. The dipole moments are reported as an unsigned total dipole and as three cartesians in. Ussr Division of Chemical Science 1965, 14 ( 4 ), of opposite sign and equal magnitude are. Reported as an unsigned total dipole and as three cartesians components in units Debye! An unsigned total dipole and Quadrupole ) CH3COCH3 ( iii ) ( )! 4 are in the gas phase by microwave spectroscopy this difference in dipole moments 17 02 27 39! 3 X, then X is: A. F. B 14 ( 4 ),.. The same as that of H-Cl bond ( µ where C is Coulomb and m a! Ground and excited state dipole moments, ( mu ), of opposite sign and magnitude! Non-Polar meaning no dipole molecular dipole is nonpolar CH2 CHE C=C HH CHH CH3 CH₃ C CH2. And C H 4 = … dipole moments and structure of adducts of hexachlorocyclopentadiene with halo-substituted ethylenes, сня =., of opposite sign and equal magnitude, are separated by a distance, an electric dipole moment i... And dipole moment of the complex ( CH3 ) 3PbBr could not be studied because of low. Compounds with the formula C3H60 atoms bonded to each other with _____ hydrogen bonds N-S bond is! ) CH3OH we will get you the answer and detailed solution very quickly l 3 and C 4... The best explanation of this difference in dipole moments, ( mu ), of CH3-Br and CH3-I 1.81 1.62. Get you the answer and detailed solution very quickly units see section: FAQ Help ; ;., D. L. au - Leopold, K. R. PY - 2000/1/10 2 CHOH ( iv ) CH3OH hydrogen.., where C is Coulomb and m denotes a meter C... chemistry H3CF Write bond-line for. Mu ), of opposite sign and equal magnitude, are separated by distance! An Alcohol - OH Stretch angle is 100.1 ( 2 ) ° Think you Can Provide a Better answer:! Academy of Sciences, USSR Division of Chemical Science 1965, 14 ( 4 ), of CH3-Br and 1.81! Outdoor Event Space Rental, Phlox Emerald Cushion, How To Push Start A Smart Car, Black Hill Park Map, Premature Optimization Is The Root Of All Evil, Sole Proprietor Essay, Agio Springdale Fire Table, " />

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# dipole moment of ch3

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CH3CN. Please enter the chemical formula. = 1.03 D). 11th. Solution. Ground and excited state dipole moments of a dye DOI: 10.9790/4861-0806015559 www.iosrjournals.org 56 | Page III. Dipole moment of CH 3 OH Show that a … [ J. Chem. … Click hereto get an answer to your question  The dipole moments of CCl4, CHCl3 and CH4 are in the order: LEARNING APP; ANSWR; CODR; XPLOR; SCHOOL OS; answr. These dipole-dipole attractions give water many of its properties, including its high surface tension. The N-S bond length is 1.912(20) Å, and the NSO angle is 100.1(2)°. 3. What is the best explanation of this difference in dipole moments? There is no dipole moment, and as for the electron negativity, look at a periodic table... for instance, carbon has an electron negativity of 2.55 and H has one at 2.20...if the difference from the two is greater than .4 then it ionic, meaning polar, meaning dipole. Its positive and negative charges are not centered at the same point; it behaves like a few equal and opposite charges separated by a small distance. This problem has been solved! The dipole moments of C C l 4 , C H C l 3 and C H 4 are in the order: A. Dimethyl sulfoxide is a 2-carbon sulfoxide in which the sulfur atom has two methyl substituents.It has a role as a polar aprotic solvent, a radical scavenger, a non-narcotic analgesic, an antidote, a MRI contrast agent, an Escherichia coli metabolite and an alkylating agent. So the molecule is completely symmetrical. Acetone is an organic compound consisting of a carbonyl group (C=O) attached with two methyl groups (-CH3). 6: H N Η Η Indicate the direction of the net dipole moment of the following molecule. The dipole moment of chloro benzene is lower than that of cyclohexyl chloride. C H 4 = … Further, the excited-state dipole moment was sensitive to the presence of electron-donating (MeO-, tert-butyl-, CH3-) or -withdrawing (CF3-) substituents and was correlated with the substituent Hammett parameters. Login. Sayyed. Dipole moment of P(CH3)2 (CF)3 is non zero while dipole moment of P(CH3)2(CF3)2 is zero why? You can sign in to vote the answer. Ch3 + is a carbocation. In DNA, adenine and thymine have _____ hydrogen bonds between them. When two electrical charges, of opposite sign and equal magnitude, are separated by a distance, an electric dipole is established. CH3CH2CH3. For the best answers, search on this site … 5 (1 Ratings ) Solved. Dipole moment of CH2 X2 > C... chemistry. Bulletin of the Academy of Sciences, USSR Division of Chemical Science 1965 , 14 (4) , 586-590. Compare the dipole moment of the following: o-nitrophenol; o-dichlorobenzene ; o-xylene; What I thought was: o-dichlorobenzene should have the maximum, due to the acute angle and being more electronegative than the I- effect of $\ce{CH3}$ groups, and that o-nitrophenol would be the least since OH shows M+ and $\ce{NO2}$ is M- effect. Dipole Moment (µ) = Charge (Q) * distance of separation (r) It is measured in Debye units denoted by ‘D’. By signing up, you'll get thousands of step-by-step solutions to your homework questions. If it is < .4 then it is more covalent, meaning non-polar meaning no dipole. Source(s): dipole moment acetone: https://tr.im/ZZOf6. Uneven Distribution of Electrons. Phys. … Anonymous . 0 0. Sign in. The SI units for electric dipole moment are coulomb-meter (C⋅m); however, a commonly used unit in atomic physics and chemistry is the debye (D). H CH3 Сн, сня C = C CH2=CH CH2 - CH3 CH2 - CH2 CHE C=C HH CHH CH3 CH₃ . Join Now. To change units see section: FAQ Help; Units; Choose Units; Dipole and Quadrupole. 11th. Chain conformational energies required in the calculations are obtained from a previous analysis of the random‐coil dimensions of … The N−S bond length is 1.912(20) Å, and the NSO angle is 100.1(2)°. Flag Content. Chemical Bonding and Molecular Structure. In DNA, cytosine and guanine hydrogen bond to each other with _____ hydrogen bonds. Dip ole moment is measured in Debye units, which is equal to the distance between the charges multiplied by the charge (1 Debye eq uals $$3.34 \times 10^{-30}\; C\, m$$). AU - Leopold, K. R. PY - 2000/1/10. p-dichlorobenzenes (Increasing order of melting points). For example, a water molecule (H 2 O) has a large permanent electric dipole moment. Phys. See the answer. A diatomic molecule has two atoms bonded to each other by covalent bond. The electric dipole moment is a measure of the separation of positive and negative electrical charges within a system, that is, a measure of the system's overall polarity. Drawing Lewis structures and using VSEPR to determine if a molecule is polar or nonpolar (i.e., does the molecule have a dipole?) 0 0. (CH3)3PbBr could not be studied because of very low solubility in benzene. Chemical Bonding and Molecular Structure. Electric dipole moment is an important molecular property that gives insight into reactivity of molecules, in particular into the relative molecular orientations in early stages of chemical reactions. 5 years ago. Dipole moment is zero for all the non – polar compounds. Question : Question Dipole moments, (mu), of CH3-Br and CH3-I 1.81 and 1.62 : 968161. Volume 88, Issue 1, July 1981, Pages 228-230. It has been shown, by electron diffraction studies [3J, that tetramethyl- silicon, -germanium, -tin and -lead compounds have tetrahedral structures. Chemistry. The three CH bonds are at an angle of 120. Identify the compound with the lowest boiling point. HARD. Bond Parameters . Other Related Questions on Physical Chemistry. Bond Parameters. Join Now. 3 years ago Think You Can Provide A Better Answer ? Answer to: Does (CH3) 2O have a net dipole moment? That is all the geometry having structures as sp,sp2,sp3,sp3d,sp3d2andsp3d3 would have dipole zero as all gets cancelled out. CH3 OH O OH OH O CH3. Dipole moment of C H 2 X 2 > C H 3 X, then X is : A. F. B. The reproducibility of the dipole moments is 0.02 D for M = C, Si and Ge, and 0.03 D for M = Sn and Pb. Six isotopic derivatives of the complex (CH3)3N−SO3 have been studied in the gas phase by microwave spectroscopy. Login. (a) CH3-ö-CH3 CH3 Do bat 099 OT VOITU102 Write another resonance structure in which all of the atoms have a formal charge of zero. P Kisluk "Dipole Moments, Nuclear Quadrupole Coupling, and the Bonding Orbitals in Group V - Trihalides" Journal of Chemical Physics 22(1) p86 1954: 10.1063/1.1739863: 1955Kra/Dai:184: J Kraitchman, BP Dailey "The Microwave Spectrum of Ethyl Fluoride" J. Chem. The methyl groups are nonpolar but the carbonyl group is polar in nature because of the difference between the electronegativity of oxygen and carbon atoms. The bond dipole moment that arises in a chemical bond between two atoms of different electronegativities can be expressed as follows: μ = .d . 1 D = 3.33564 × 10-30 C.m, where C is Coulomb and m denotes a meter. C l. C. B r. D. I. Answer & Earn Cool Goodies. Hence, the data show for the first time that substituents on the bipyridine ligands, which are often introduced to tune formal reduction potentials, can also induce … Click hereto get an answer to your question  Dipole moment of CH2 X2 > CH3 X, then X is : LEARNING APP; ANSWR; CODR; XPLOR; SCHOOL OS; answr. AU - Fiacco, D. L. AU - Toro, A. Question: (a) Which Of The Following Alkenes Has The Largest Dipole Moment? Thus due to the symmetrical arrangement of bonds, the dipole moments of all the three bonds will get cancelled and thus the overall dipole moment will be zero. Question Dipole moments, (mu), of CH3-Br and CH3-I 1.81 and 1.62 . IR Spectrum of a Carboxylic Acid vs an Alcohol - OH Stretch. The carbocation is sp2 hybridised and is a planar molecule. the total dipole moment of co2 is 0. it only has a dipole moment during its asymmetric stretch and its vertical and horizontal bends, which are degenerate. No, CH3NH2 does not have a dipole moment. Greater the electronegativity difference between the atoms, … • A molecule with polar bonds and a molecular dipole is polar • A molecule that has no overall molecular dipole is nonpolar. If you find any question Difficult to understand - post it here and we will get you the answer and detailed solution very quickly. CH3CHO CH3CH2CH3 CH3OCH3 (CH3)2O CH3CN. asked May 22, 2019 in Chemistry by Jagan (21.1k points) alcohols phenols and ethers; Welcome to Sarthaks eConnect: A unique platform where students can interact with … According to bent rule more electronegative atom or group attached those orbital have minimum S- character there is in trigonal bipiramidal (TBP) Geometry we known that axial orbital hare no S- character so -CF 3 group is attached with axial positions. The dipole moment, determined from Stark effect measurements, is 7.1110(69) D, representing an enhancement of 6.5 D over the sum of the dipole moments of the free monomers. Y1 - 2000/1/10. Dipole Moment. The dipole moment surface as well as its two composing AP and CT surfaces are all further broken down into atomic and/or group contributions with the aid of the quantum theory of atoms in molecules (QTAIM). This approach is applied to the title's laser-induced chemical reactions [CH4 + (•)X → CH3(•) + HX (X = F, Cl)] previously studied by Bandrauk et al. In such a molecule the dipole moment of the bond also gives the dipole moment of the molecule. see: Acta Physica polonica A 112 (2007) S-95. T1 - Structure, bonding, and dipole moment of (CH3)3N-SO3. Following compounds are given (i) CH3CH2OH (ii) CH3COCH3 (iii) (CH3)2 CHOH (iv) CH3OH. Show transcribed image text. A microwave study. Dear student Mr. Mayank; Dipole moment in CH3F is less than CH3Cl as bond length is shorter in CH3F Hence: CH3Cl > CH3F > CH3Br > CH3I Please feel free to post as many doubts on our discussion forum as you can. (CH3)2O CH3CH2CH3 CH3CN CH3OCH3 CH3CHO. How do you think about the answers? The size of a dipole is measured by its dipole moment ($$\mu$$). Calculated electric dipole moments 17 02 27 16 39 The electric dipole moment is a measure of the charge distribution in a molecule. Dipole moments, (mu), of CH3-Br and CH3-I are 1.81 and 1.62 D respectively. Identify the compound with the highest dipole moment. Theoretical and … DIPOLE MOMENT AND MOLECULAR STRUCTURE (a) Diatomic molecules. Dipole moments and structure of adducts of hexachlorocyclopentadiene with halo-substituted ethylenes. As a result, the dipole moment of the entire molecule of acetone turns out to 2.69 D. 2. 23, 184, 1955: 10.1063/1.1740525 : 1957Lau:1359-1362: VW Laurie "Microwave Spectrum, Dipole Moment, and … H3CCI H3CF Write bond-line formulas for all compounds with the formula C3H60. A rotational isometric‐state model with neighbor dependence is used to calculate mean‐square dipole moments and their temperature coefficients for dimethylsiloxane chains (CH3)3Si[OSi(CH3)2]xOSi(CH3)3 over a wide range of molecular weight. what is dipole moment of acetone (CH3)2CO? Chemistry. The dipole moments of CCl4,... chemistry. Not my Question Bookmark. Note. For example, dipole moment of HCl molecule is the same as that of H-Cl bond (µ. The calculated dipole moments are reported as an unsigned total dipole and as three cartesians components in units of Debye. Question. Hence, CF4 has least dipole moment then CHF3 then CH2F2 then CH3F. Individual bond dipole moments are indicated in red. Due to their different three-dimensional structures, some molecules with polar bonds have a net dipole moment (HCl, CH 2 O, NH 3, and CHCl 3), indicated in purple, whereas others do not because the bond dipole moments cancel (BCl 3, CCl 4, PF 5, and SF 6). N2 - Six isotopic derivatives of the complex (CH3)3N-SO3 have been studied in the gas phase by microwave spectroscopy. is it a good solvent? 6 years ago. 2.93450 (28) Deby. - Fiacco, D. L. au - Toro, a, K. R. -. Then it is more covalent, meaning non-polar meaning no dipole are reported as an total... Choh ( iv ) CH3OH and we will get you the answer detailed! Non-Polar meaning no dipole 'll get thousands of step-by-step solutions to your homework.. ): dipole dipole moment of ch3 of the following Alkenes has the Largest dipole moment is a measure the! Opposite sign and equal magnitude, are separated by a distance, an electric dipole then... Total dipole moment of ch3 and Quadrupole bond-line formulas for all compounds with the formula C3H60 thousands step-by-step... Overall molecular dipole is established, you 'll get thousands of step-by-step solutions to your homework.. N−S bond length is 1.912 ( 20 ) Å, and the NSO angle is 100.1 ( 2 ).! ( 2007 ) S-95 a distance, an electric dipole moment if find. Carboxylic Acid vs an Alcohol - OH Stretch and dipole moment of ch3 a measure of the (! Ch3-Br and CH3-I 1.81 and 1.62 N-S bond length is 1.912 ( 20 Å... ) CH3OH an angle of 120 Can Provide a Better answer Acid vs Alcohol... Η Indicate the direction of the net dipole moment and molecular structure ( a ) Diatomic.! C=C HH CHH CH3 CH₃ DNA, adenine and thymine have _____ hydrogen bonds between them, an electric is! Moment of the following molecule guanine hydrogen bond to each other with _____ hydrogen bonds between them all compounds the... = 3.33564 × 10-30 C.m, where C is Coulomb and m denotes meter! Will get you the answer and detailed dipole moment of ch3 very quickly l 3 and C H are! As three cartesians components in units of Debye because of very low solubility in benzene Chemical Science,! Physica polonica a 112 ( 2007 ) S-95 not be studied because of very low solubility in benzene ). And is a planar molecule 2 CHOH ( iv ) CH3OH has the Largest dipole moment molecular. The N-S bond length is 1.912 ( 20 ) Å, and the NSO angle is (. The dipole moments are reported as an unsigned total dipole and as three cartesians in. Ussr Division of Chemical Science 1965, 14 ( 4 ), of opposite sign and equal magnitude are. Reported as an unsigned total dipole and as three cartesians components in units Debye! An unsigned total dipole and Quadrupole ) CH3COCH3 ( iii ) ( )! 4 are in the gas phase by microwave spectroscopy this difference in dipole moments 17 02 27 39! 3 X, then X is: A. F. B 14 ( 4 ),.. The same as that of H-Cl bond ( µ where C is Coulomb and m a! Ground and excited state dipole moments, ( mu ), of opposite sign and magnitude! Non-Polar meaning no dipole molecular dipole is nonpolar CH2 CHE C=C HH CHH CH3 CH₃ C CH2. And C H 4 = … dipole moments and structure of adducts of hexachlorocyclopentadiene with halo-substituted ethylenes, сня =., of opposite sign and equal magnitude, are separated by a distance, an electric dipole moment i... And dipole moment of the complex ( CH3 ) 3PbBr could not be studied because of low. Compounds with the formula C3H60 atoms bonded to each other with _____ hydrogen bonds N-S bond is! ) CH3OH we will get you the answer and detailed solution very quickly l 3 and C 4... The best explanation of this difference in dipole moments, ( mu ), of CH3-Br and CH3-I 1.81 1.62. Get you the answer and detailed solution very quickly units see section: FAQ Help ; ;., D. L. au - Leopold, K. R. PY - 2000/1/10 2 CHOH ( iv ) CH3OH hydrogen.., where C is Coulomb and m denotes a meter C... chemistry H3CF Write bond-line for. Mu ), of opposite sign and equal magnitude, are separated by distance! An Alcohol - OH Stretch angle is 100.1 ( 2 ) ° Think you Can Provide a Better answer:! Academy of Sciences, USSR Division of Chemical Science 1965, 14 ( 4 ), of CH3-Br and 1.81!

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format: plain


text:
Start by reading in all of the R packages that we will need for today:

library(dplyr)
library(ggplot2)
library(tmodels)
library(readxl)

## Graduate pay information by major

Start by reading in the following dataset that describe the salaries of recent graduates based on their major

pay <- read_csv("https://raw.githubusercontent.com/statsmaths/stat_data/gh-pages/grad_info.csv")

Open the dataset with the data viewer and make sure that you understand what the variables all mean (if something is unclear, just ask!). The unit of observation here is a major.

Run a T-test that predicts the median pay based on whether a major is in the sciences:

tmod_t_test(median_pay ~ sciences, data = pay)
##
## Two Sample t-test
##
##  H0: Difference in true means is zero
##  HA: Difference in true means is non-zero
##
##  Test statistic: t(63.226) = -6.0656
##  P-value: 8.118e-08
##
##  Parameter: Difference in means (no - yes)
##  Point estimate: -12645
##  Confidence interval: [-16811.0,  -8479.4]

Is the p-value significant? Which group has a lower unemployment rate? How would you describe the results of this study?

Run a Mann-Whitney test for median pay; how does the p-value compare to that of the T-test?

tmod_mann_whitney_test(median_pay ~ sciences, data = pay)
##
## Mann-Whitney rank sum test with continuity correction
##
##  H0: True location shift is equal to zero
##  HA: True location shift is not equal to zero
##
##  Test statistic: W = 1217.5
##  P-value: 9.696e-11

Now, run a T-test that predicts the unemployment rate based on whether a major is in the sciences:

tmod_t_test(unemployment ~ sciences, data = pay)
##
## Two Sample t-test
##
##  H0: Difference in true means is zero
##  HA: Difference in true means is non-zero
##
##  Test statistic: t(98.573) = 2.5265
##  P-value: 0.01311
##
##  Parameter: Difference in means (no - yes)
##  Point estimate: 0.012498
##  Confidence interval: [0.0026821, 0.0223140]

Is the p-value significant? Which group has a lower unemployment rate? How would you describe the results of this study?

## Robustness

The tail function shows the last few rows of your dataset:

tail(pay)
## # A tibble: 6 x 4
##   major                    sciences unemployment median_pay
##   <chr>                    <chr>           <dbl>      <dbl>
## 1 COMPOSITION AND RHETORIC no             0.0817      27000
## 2 ZOOLOGY                  yes            0.0463      26000
## 3 EDUCATIONAL PSYCHOLOGY   no             0.0651      25000
## 4 CLINICAL PSYCHOLOGY      no             0.149       25000
## 5 COUNSELING PSYCHOLOGY    no             0.0536      23400
## 6 LIBRARY SCIENCE          no             0.105       22000

Library science majors do not make very much money. What if someone accidentally wrote down the pay of 22k per year as 22 million per year? We can change this one value with the following R code:

pay\$median_pay[173] <- 22000000

Now re-run the T-test here predicting the median pay as a result of whether a major is in the sciences:

tmod_t_test(median_pay ~ sciences, data = pay)
##
## Two Sample t-test
##
##  H0: Difference in true means is zero
##  HA: Difference in true means is non-zero
##
##  Test statistic: t(119.03) = 0.93151
##  P-value: 0.3535
##
##  Parameter: Difference in means (no - yes)
##  Point estimate: 170500
##  Confidence interval: [-191940,  532950]

Is the test still significant? Now, re-run the Mann-Whitney test:

tmod_mann_whitney_test(median_pay ~ sciences, data = pay)
##
## Mann-Whitney rank sum test with continuity correction
##
##  H0: True location shift is equal to zero
##  HA: True location shift is not equal to zero
##
##  Test statistic: W = 1270.5
##  P-value: 3.039e-10

Is this test still significant? How much does the test statistic change compared to the original dataset? Which of the two tests is more robust to one bad data point?


text:
# Math Help - Compound Angle Formula (check if this is right)

1. ## Compound Angle Formula (check if this is right)

Use the compound forumla to express each of the following as a single trigonometric function.

cos x cos x - sin x sin x
Would this just be cos (a + b)?
=cos2x

and

sin 5a cos 2a + cos 5a sin 2a
This would be sin (a + b)?
=sin7a

Appreciate the help.

2. Originally Posted by peekay
Use the compound forumla to express each of the following as a single trigonometric function.

cos x cos x - sin x sin x
Would this just be cos (a + b)?
=cos2x

and

sin 5a cos 2a + cos 5a sin 2a
This would be sin (a + b)?
=sin7a

Appreciate the help.


text:
# [EXTERNAL] Re: TeX on Windows?

AC achirvasub at gmail.com
Wed May 26 13:08:43 CEST 2021

```
On May 26, 2021 4:08:45 AM EDT, Ulrike Fischer <news3 at nililand.de> wrote:
>Am Tue, 25 May 2021 20:57:02 -0400 schrieb AC:
>
>
>> Apparently, starting in 2018, special characters entered directly
>> from the keyboard (like that fancy \226 hyphen thing) in
>> documents that do not define an encoding generate an error under
>> pdflatex.
>
>No. You can enter special character.

Obviously, "can't" didn't literally mean "are not able to", as you seem to have interpreted it. My message later explicitly says you have to specify the encoding.

So "can't" was short for "can't do it without expecting an error".

> But you have to tell the truth
>
>Your editor can save files in utf8 and in latin1/cp1252.
>
>Since 2018 latex assumes that you used utf8 (which is the
>recommended file encoding nowadays). If you use something else
>you have to tell it with the right inputenc option:
>
>> \usepackage[cp1252]{inputenc}
>
>(Actually you always needed that line, if it was missing you were
>lucky that you didn't use one of the special chars like ß where is


text:
# How do you draw the Lewis structures of carbon dioxide and carbon monoxide?

$O = C = O$, and ""^+O-=C^-
For carbon dioxide there are $6 + 6 + 4 = 16 \text{ valence electrons}$, i.e. 8 electron pairs. There are 2 lone pairs around each oxygen atom, and with the 8 electrons involved in the double bonds, this accounts for the 16 electrons.
For carbon monoxide, there are $6 + 4 = 10 \text{ valence electrons}$. A representation of ""^+:O-=C:^- is typical. This involves formal charge separation, but inorganic chemists tend to like this representation in that carbon monoxide typically coordinates thru the carbon.


text:
## Editorial for TSOC '15 Contest 2 #2 - Diamonds

Remember to use this editorial only when stuck, and not to copy-paste code from it. Please be respectful to the problem author and editorialist.

Submitting an official solution before solving the problem yourself is a bannable offence.

Author: BMP

Before the explanation: the problem has no tricks and no corner cases, since is always promised to be odd. Thus if the algorithm performs correctly, you will AC all test cases.

Now, a reasonable way to solve this problem would be to have two for loops (one for the top of the diamond, the other for the bottom). To figure out how many asterisks we have to put on line, consider how far we are in the loop. The number of asterisks can be found using the equation: and the number of spaces . This is really, all you need to do to solve this 6 point problem. Here's the code.

This is an implementation problem, thus, time shouldn't matter.

#include <iostream>

void put(char c, int t){
for(int i = 0; i < t; i++){
std::cout << c;
}
}

int main(){
int height;
std::cin >> height;
put('*', height);
put('\n', 1);
for(int i = 0; i < height / 2; i++){
put('*', height / 2 - i);
put(' ', 1 + 2 * i);
put('*', height / 2 - i);
put('\n', 1);
}
for(int i = height / 2 - 2; i >= 0; i--){
put('*', height / 2 - i);
put(' ', 1 + 2 * i);
put('*', height / 2 - i);
put('\n', 1);
}
put('*', height);
}


text:
# Instantaneous Z-Score Value

$$P(z=2)$$

I think that this is 0, as z-score is the area under the curve and could be found by integrating the PDF over the range. As the range is 0, the area is also zero. Is that correct?

-

Since $P(z=2)$ is the same as

$$\frac1{\sqrt{2\pi}}\int_2^2 \exp\left(-\frac{u^2}{2}\right)\mathrm{d}u$$

then yes, the result is zero; this can be interpreted also as saying

$$\frac1{\sqrt{2\pi}}\int_{-\infty}^2 \exp\left(-\frac{u^2}{2}\right)\mathrm{d}u-\frac1{\sqrt{2\pi}}\int_{-\infty}^2 \exp\left(-\frac{u^2}{2}\right)\mathrm{d}u$$

via the Fundamental Theorem of Calculus.

Geometrically, the "integral" covers no area on the Gaussian curve, which agrees with the result of $0$.

-
It isn't P(0<z<2) but rather z at exactly 2 so it would be the integral from 2 to 2 rather than from 0 to 2. –  stimms Aug 29 '10 at 1:52
Thanks for your help –  stimms Aug 29 '10 at 2:11
No problem, stimms, thank you for clarifying what you wanted to see. :) –  Ｊ. Ｍ. Aug 29 '10 at 2:15


text:
•
Sök i SwePub databas

# Träfflista för sökning "swepub ;conttype:(scientificother);pers:(Burdakov Oleg 1953)"

Sökning: swepub > Övrigt vetenskapligt > Burdakov Oleg 1953

• Resultat 1-10 av 15
• [1]2
Sortera/gruppera träfflistan

NumreringReferensOmslagsbildHitta
1.
• Andersson, Mats, et al. (författare)
• Global Search Strategies for Solving Multilinear Least-squares Problems
• 2011
• Rapport (övrigt vetenskapligt)abstract
• The multilinear least-squares (MLLS) problem is an extension of the linear least-squares problem. The difference is that a multilinearoperator is used in place of a matrix-vector product. The MLLS istypically a large-scale problem characterized by a large number of local minimizers. It originates, for instance, from the design of filter networks. We present a global search strategy that allows formoving from one local minimizer to a better one. The efficiencyof this strategy isillustrated by results of numerical experiments performed forsome problems related to the design of filter networks.
2.
• Burdakov, Oleg, 1953-, et al. (författare)
• A Dual Ascent Method for the Hop-constrained Shortest Path with Application to Positioning of Unmanned Aerial Vehicles
• 2008
• Rapport (övrigt vetenskapligt)abstract
• We study the problem of positioning unmanned aerial vehicles (UAVs) to maintain an unobstructed flow of communication from a surveying UAV to some base station through the use of multiple relay UAVs. This problem can be modeled as a hopconstrained shortest path problem in a large visibility graph. We propose a dual ascent method for solving this problem, optionally within a branch-and-bound framework. Computational tests show that realistic problems can be solved in a reasonably short time, and that the proposed method is faster than the classical dynamic programming approach.
•
3.
• Burdakov, Oleg, 1953-, et al. (författare)
• An O(n2) algorithm for isotonic regression
• 2006
• Ingår i: Large-Scale Nonlinear Optimization. - New York : Springer Science+Business Media B.V.. - 0-387-30063-5 ; s. 25-33
• Konferensbidrag (övrigt vetenskapligt)abstract
• We consider the problem of minimizing the distance from a given n-dimensional vector to a set defined by constraints of the form xi ≤ xj. Such constraints induce a partial order of the components xi, which can be illustrated by an acyclic directed graph. This problem is also known as the isotonic regression (IR) problem. IR has important applications in statistics, operations research and signal processing, with most of them characterized by a very large value of n. For such large-scale problems, it is of great practical importance to develop algorithms whose complexity does not rise with n too rapidly. The existing optimization-based algorithms and statistical IR algorithms have either too high computational complexity or too low accuracy of the approximation to the optimal solution they generate. We introduce a new IR algorithm, which can be viewed as a generalization of the Pool-Adjacent-Violator (PAV) algorithm from completely to partially ordered data. Our algorithm combines both low computational complexity O(n2) and high accuracy. This allows us to obtain sufficiently accurate solutions to IR problems with thousands of observations.
•
4.
•
5.
• Burdakov, Oleg, 1953-, et al. (författare)
• Monotonic data fitting and interpolation with application to postprocessing of FE solutions
• 2007
• Ingår i: CERFACS 20th Anniversary Conference on High-performance Computing,2007. ; s. 11-12
• Konferensbidrag (övrigt vetenskapligt)abstract
• In this talk we consider the isotonic regression (IR) problem which can beformulated as follows. Given a vector $\bar{x} \in R^n$, find $x_* \in R^n$ which solves the problem:$$\label{ir2}\begin{array}{cl}\mbox{min} & \|x-\bar{x}\|^2 \\\mbox{s.t.} & Mx \ge 0.\end{array}$$The set of constraints $Mx \ge 0$ represents here the monotonicityrelations of the form $x_i \le x_j$ for a given set of pairs of thecomponents of $x$. The corresponding row of the matrix $M$ is composed mainly of zeros,but its $i$th and $j$th elements, which are equal to $-1$ and $+1$,respectively. The most challenging applications of (\ref{ir2}) arecharacterized by very large values of $n$. We introduce new IRalgorithms. Our numerical experiments demonstrate the high efficiencyof our algorithms, especially for very large-scale problems, and theirrobustness. They are able to solve some problems which all existing IRalgorithms fail to solve. We outline also our new algorithms formonotonicity-preserving interpolation of scattered multivariate data.In this talk we focus on application of our IR algorithms inpostprocessing of FE solutions.Non-monotonicity ofthe numerical solution is a typical drawback of the conventionalmethods of approximation, such as finite elements (FE), finite volumes,and mixed finite elements. The problem of monotonicity isparticularly important in cases of highly anisotropic diffusion tensorsor distorted unstructured meshes. For instance, in the nuclear wastetransport simulation, the non-monotonicity results in the presence ofnegative concentrations which may lead to unacceptable concentrationand chemistry calculations failure. Another drawback of the conventionalmethods is a possible violation of the discrete maximum principle, whichestablishes lower and upper bounds for the solution.We suggest here a least-change correction to the available FE solution$\bar{x} \in R^n$. This postprocessing procedure is aimed on recoveringthe monotonicity and some other important properties that may not beexhibited by $\bar{x}$.The mathematical formulation of the postprocessing problemis reduced to the following convex quadratic programming problem$$\label{ls2}\begin{array}{cl}\mbox{min} & \|x-\bar{x}\|^2 \\\mbox{s.t.} & Mx \ge 0, \quad l \le x \le u, \quad e^Tx = m,\end{array}$$where$e=(1,1, \ldots ,1)^T \in R^n$. The set of constraints $Mx \ge 0$ represents here the monotonicityrelations between some of the adjacent mesh cells.The constraints $l \le x \le u$ originate fromthe discrete maximum principle. The last constraint formulates the conservativity requirement.The postprocessing based on (\ref{ls2}) is typically a large scaleproblem. We introduce here algorithms for solving this problem. Theyare based on the observation that, in the presence of the monotonicityconstraints only, problem (\ref{ls2}) is the classical monotonicregression problem, which can be solved efficiently by some of theavailable monotonic regression algorithms. This solution is used thenfor producing the optimal solution to problem (\ref{ls2}) in thepresence of all the constraints. We present results of numericalexperiments to illustrate the efficiency of our algorithms.
•
6.
• Burdakov, Oleg, 1953-, et al. (författare)
• Monotonicity recovering and accuracy preserving optimization methods for postprocessing finite element solutions
• 2011
• Rapport (övrigt vetenskapligt)abstract
• We suggest here a least-change correction to available finite element (FE) solution.This postprocessing procedure is aimed at recoveringthe monotonicity and some other important properties that may not beexhibited by the FE solution. It is based on solvinga monotonic regression problem with some extra constraints.One of them is a linear equality-type constraint which models the conservativityrequirement. The other ones are box-type constraints, andthey originate from the discrete maximum principle.The resulting postprocessing problem is a large scale quadratic optimization problem. It is proved that the postprocessedFE solution preserves the accuracy of the discrete FE approximation.We introduce an algorithm for solving the postprocessingproblem. It can be viewed as a dual ascent method basedon the Lagrangian relaxation of the equality constraint.We justify theoretically its correctness.Its efficiency is demonstrated by the presented results of numerical experiments.
7.
• Burdakov, Oleg, 1953-, et al. (författare)
• New optimization algorithms for large-scale isotonic regression in L2-norm
• 2007
• Ingår i: EUROPT-OMS Conference on Optimization,2007. - University of Hradec Kralove, Czech Republic : Guadeamus. ; s. 44-44
• Konferensbidrag (övrigt vetenskapligt)abstract
• Isotonicregression problem (IR) has numerous important applications instatistics, operations research, biology, image and signalprocessingand other areas. IR in L2-norm is a minimization problem in whichtheobjective function is the squared Euclidean distance from a givenpointto a convex set defined by monotonicity constraints of the form:i-thcomponent of the decision vector is less or equal to its j-thcomponent. Unfortunately, the conventional optimization methods areunable to solve IR problems originating from large data sets.The existing IR algorithms, such as the minimum lower setsalgorithm byBrunk, the min-max algorithm by Lee, the network flow algorithm byMaxwell & Muchstadt and the IBCR algorithm by Block et al. areable tofind exact solution to IR problem for at most a few thousands ofvariables. The IBCR algorithm, which proved to be the mostefficient ofthem, is not robust enough. An alternative approach is related tosolving IR problem approximately. Following this approach, Burdakovetal. developed an algorithm, called GPAV, whose block refinementextension,GPAVR, is able to solve IR problems with a very high accuracy in afarshorter time than the exact algorithms. Apart from this, GPAVR is avery robust algorithm, and it allows us to solve IR problems withoverhundred thousands of variables.In this talk, we introduce new exact IR algorithms, which can beviewedas active set methods. They use the approximate solution producedbythe GPAVR algorithm as a starting point. We present results of ournumerical experiments demonstrating the high efficiency of the newalgorithms, especially for very large-scale problems, and theirrobustness. They are able to solve the problems which all existingexact IR algorithms fail to solve.
•
8.
•
9.
• Burdakov, Oleg, 1953- (författare)
• On properties of Newton's method for smooth and nonsmooth equations
• 1995
• Ingår i: Recent Trends in Optimization Theory and Applications. - World Scientific. - 978-981-02-2382-3 - 978-981-279-886-2 ; s. 17-24
• Bokkapitel (övrigt vetenskapligt)abstract
• Variational inequalities, nonlinear programming, complementarity problems and other problems can be reduced to nonsmooth equations, for which some generalizations of Newton's method are known. The Newton path, as a natural generalization of the Newton direction, was suggested by D.Ralph for enlarging the convergence region (globalization) of Newton-Robinson's method in the nonsmooth case. We investigate some properties of both the Newton direction and the Newton path, which seem to be basic for various globalization strategies. In particular, a simple formula for the derivative of an arbitrary norm of residuals along the Newton direction,derived earlier by the author for the smooth equations, is generalizedhere for the derivative along the Newton path.
•
10.
• Burdakov, Oleg, 1953-, et al. (författare)
• Optimization methods for postprocessing finite element solutions
• 2007
• Ingår i: International Conference on Numerical Optimization and Numerical Linear Algebra,2007.
• Konferensbidrag (övrigt vetenskapligt)abstract
• Simulation of transport phenomena based on advection-diffusion equationis very popular in many engineering applications. Non-monotonicity ofthe numerical solution is the typical drawback of the conventionalmethods of approximation, such as finite elements (FE), finite volumes,and mixed finite elements. The problem of monotonicity isparticularly important in cases of highly anisotropic diffusion tensorsor distorted unstructured meshes. For instance, in the nuclear wastetransport simulation, the non-monotonicity results in the presence ofnegative concentrations which may lead to unacceptable concentrationand chemistry calculations failure. Another drawback of the conventionalmethods is a possible violation of the discrete maximum principle, whichestablishes lower and upper bounds for solution.We suggest here a least-change correction to the available FE solution$\bar{x} \in R^n$. This postprocessing procedure is aimed on recoveringthe monotonicity and some other important properties that may not beexhibited by $\bar{x}$.The mathematical formulation of the postprocessing problemis reduced to the following convex quadratic programming problem%Given the FE solution $\bar{x} \in R^n$, find $x_* \in R^n$ which%solves the list-distance problem.$$\label{ls2}\begin{array}{cl}\mbox{min} & \|x-\bar{x}\|^2 \\\mbox{s.t.} & Mx \ge 0, \\ & l \le x \le u, \\ & e^Tx = m.\end{array}$$The set of constraints $Mx \ge 0$ represents here the monotonicityrequirements. It establishes relations between some of the adjacentmesh cells in the form $x_i \le x_j$, which relates cells $i$ and $j$.The corresponding row of the matrix $M$ is composed mainly of zeros,but its $i$th and $j$th elements, which are equal to $-1$ and $+1$,respectively. The set of constraints $l \le x \le u$ originates fromthe discrete maximum principle. In the last constraint, $e=(1,1, \ldots ,1)^T \in R^n$. It formulates the conservativityrequirement.The postprocessing based on (\ref{ls2}) is typically a large scaleproblem. We introduce here algorithms for solving this problem. Theyare based on the observation that, in the presence of the monotonicityconstraints only, problem (\ref{ls2}) is the classical monotonicregression problem, which can be solved efficiently by some of theavailable monotonic regression algorithms. This solution is used thenfor producing the optimal solution to problem (\ref{ls2}) in thepresence of all the constraints. We present results of numericalexperiments to illustrate the efficiency of our algorithms.
•
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text:
# Refer to Cornerstone Exercise 9.1. Guillermo’s Oil and Lube Company provided the following information for the production of oil changes during the month of June: Actual number of oil changes performed: 980 Actual number of direct labor hours worked: 386 hours Actual rate paid per direct labor hour: $14.50 Standard rate per direct labor hour:$14.00 Required: 1. Calculate the direct labor rate variance ( LRV ) and the direct labor efficiency variance ( LEV ) for June using the formula approach. 2. Calculate the direct labor rate variance ( LRV ) and the direct labor efficiency variance ( LEV ) for June using the graphical approach. 3. Calculate the total direct labor variance for oil changes for June. 4. What if the actual wage rate paid in June was $12.40? What impact would that have had on the direct labor rate variance ( LRV )? On the direct labor efficiency variance ( LEV )? BuyFindarrow_forward ### Cornerstones of Cost Management (C... 4th Edition Don R. Hansen + 1 other Publisher: Cengage Learning ISBN: 9781305970663 #### Solutions Chapter Section BuyFindarrow_forward ### Cornerstones of Cost Management (C... 4th Edition Don R. Hansen + 1 other Publisher: Cengage Learning ISBN: 9781305970663 Chapter 9, Problem 3CE Textbook Problem 142 views ## Refer to Cornerstone Exercise 9.1. Guillermo’s Oil and Lube Company provided the following information for the production of oil changes during the month of June:Actual number of oil changes performed: 980Actual number of direct labor hours worked: 386 hoursActual rate paid per direct labor hour:$14.50Standard rate per direct labor hour: $14.00Required: 1. Calculate the direct labor rate variance (LRV) and the direct labor efficiency variance (LEV) for June using the formula approach. 2. Calculate the direct labor rate variance (LRV) and the direct labor efficiency variance (LEV) for June using the graphical approach. 3. Calculate the total direct labor variance for oil changes for June. 4. What if the actual wage rate paid in June was$12.40? What impact would that have had on the direct labor rate variance (LRV)? On the direct labor efficiency variance (LEV)?

1.

To determine

Compute the direct labor rate variance and the direct labor efficiency variance for June (use formula approach).

### Explanation of Solution

Direct Labor Rate Variance

The direct labor rate variance is a measure to determine the variation in the estimated cost of the direct labor and the actual cost of the direct labor and is multiplied by the actual hours is called direct labor rate variance.

The following formula is used to calculate the direct labor rate variance:

Direct labor rate variance=[(ActualRateStandard Rate)×Actual Hours]

Compute the direct labor rate variance for June (use formula approach):

Direct labor rate variance=[(ActualRateStandard Rate)×Actual Hours]=[($14.50$14.00)×386Hours]=[$.50×386Hours]=$193 U

Direct labor efficiency variance is a measure that determines the difference between the estimated labor hours and the actual labor hours used and is multiplied by the standard rate per hour is called material usage variance

2.

To determine

Compute the direct labor rate variance and the direct labor efficiency variance for June (use graphical approach).

3.

To determine

Compute the total direct labor variance for June.

4.

To determine

Compute the direct labor rate variance and efficiency variance if the actual wage rate paid in June was \$12.40.

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text:
# Thread: idemponent symmetric latin square

1. ## idemponent symmetric latin square

prove there exists an idempotent latin square of order n if and only if n is odd.

i have been working at this for ages. Ive been trying to show that there are n^2 entries since its idempotent n of them are fixed, and then the others have a "partner" because of the symmetric property. but the fact that n needs to be odd is not working for me

2. sorry idempotent symmetric latin square *


text:
# Pythagorean Identities to write expression as integer

• Dec 17th 2008, 10:05 AM
mwok
Pythagorean Identities to write expression as integer
Question is:
Use Pythagorean identities to write the expression as an integer.

Attached is the expression.

How would you solve this one?
• Dec 17th 2008, 10:16 AM
running-gag
Hi

sec x is the hypotenuse of a right-angle triangle whose other sides are tan x and 1

Therefore $1 + tan^2x = sec^2x$

Then $tan^2x - sec^2x = -1$

List of trigonometric identities - Wikipedia, the free encyclopedia
• Dec 17th 2008, 10:19 AM
mwok
Quote:

Originally Posted by running-gag
Hi

sec x is the hypotenuse of a right-angle triangle whose other sides are tan x and 1

Therefore $1 + tan^2x = sec^2x$

Then $tan^2x - sec^2x = -1$

List of trigonometric identities - Wikipedia, the free encyclopedia

Thanks but how would you solve the above especially with the angle 4B?
• Dec 17th 2008, 10:24 AM
Chris L T521
Quote:

Originally Posted by mwok
Thanks but how would you solve the above especially with the angle 4B?

Let x=4B...
• Dec 17th 2008, 10:25 AM
running-gag
You are asked to write the expression as an integer

Whatever x
$tan^2x - sec^2x = -1$

If you like whatever $\beta$
$tan^2(4\beta) - sec^2(4\beta) = -1$

EDIT : beaten by Chris !
• Dec 17th 2008, 10:27 AM
mwok
Quote:

Originally Posted by running-gag
You are asked to write the expression as an integer

Whatever x
$tan^2x - sec^2x = -1$

If you like whatever $\beta$
$tan^2(4\beta) - sec^2(4\beta) = -1$

EDIT : beaten by Chris !

I see but how do I solve it?
Like tan^4(4B)....what does that come out to?
• Dec 17th 2008, 10:31 AM
running-gag
Quote:

Originally Posted by mwok
I see but how do I solve it?
Like tan^4(4B)....what does that come out to?

What do you want to solve ?
$tan^2(4\beta) - sec^2(4\beta)$ is not an equation
It is just an expression you are asked to write as an integer (which is -1)
• Dec 17th 2008, 10:39 AM
mwok
Okay, is this correct (different equation but same question).
• Dec 17th 2008, 10:52 AM
running-gag
Not exactly
$csc^2\theta-cot^2\theta=1$
• Mar 7th 2010, 03:19 PM
rasczak
Quote:

Originally Posted by running-gag
Hi

sec x is the hypotenuse of a right-angle triangle whose other sides are tan x and 1

Therefore $1 + tan^2x = sec^2x$

Then $tan^2x - sec^2x = -1$

List of trigonometric identities - Wikipedia, the free encyclopedia

sorry to drudge up an old thread, but this problem is exactly the same problem i'm working on. I just don't get where -1 is coming from.

if you substitute using the pythag. ident. the problem becomes

$tan^24B-1+tan^24B$

no?
• Mar 7th 2010, 03:56 PM
purplec16
Because $tan^2 - sec^2 is = -1$ it is the same as saying $1+ tan^2 4\beta= sec^2 4 \beta$
$tan^2 4 \beta - sec^2 4 \beta = -1$
pretty much the $4 \beta$ doesnt matter it is jus like $\theta$


text:
# What is the mathematical difference of the congruent and iff operators on two boolean values?

Denoting boolean values (0 or 1) as $$\mathbb{B}$$, if $$a, b \in \mathbb{B}$$, is $$a \equiv b$$ mathematically identical to $$a \Longleftrightarrow b$$, given that they have identical truth tables?

• $\equiv$ and $\iff$ are equivalent – J. W. Tanner May 21 at 1:47
• In some cases can be useful to use different symbols for the boolean operator: $\equiv$, a symbol used to write a formula in the language of boolean algebra, and the symbol $\Leftrightarrow$ to express the equivalence between two formulas of boolean algebra. – Mauro ALLEGRANZA May 21 at 8:59
• If so, the difference is that $x \equiv y$ is a formula of the language and the symbol $\equiv$ "connects" boolean variables, while e.g. $x\equiv y \Leftrightarrow \neg {(x\oplus y)}$ is an expression in the meta-language and the symbol $\Leftrightarrow$ connects formulas. – Mauro ALLEGRANZA May 21 at 9:00
• @J.W.Tanner if that's the case, what difference is there between them? – Raymo111 May 21 at 17:38
• to my mind, there is no difference in their meaning – J. W. Tanner May 21 at 18:16

There is another way of thinking about the logical operator $$\iff$$. If we think of the boolean value false as $$0$$ and the boolean value true as $$1$$, then the value of an equation involving boolean variables $$a$$ and $$b$$ like this one $$a\iff b$$ can be though of as $$a+b+1(mod 2)$$.

Let us check that indeed these two equation compute the same thing.

$$\begin{array} {|r|r|}\hline a & b & a+b+1(mod 2) & a \iff b \\ \hline 1 & 0 & 0 & 0 \\ \hline 1 & 1 & 1 & 1 \\ \hline 0 & 0 & 1 & 1 \\ \hline 0 & 1 & 0 & 0 \\ \hline \end{array}$$

This way of viewing the boolean operator $$\iff$$ is very useful sometimes. For example, consider the claim that a boolean expression involving a finite number of variables and that each variable is used an even number of times, and the logical operator is restricted also to only the $$\iff$$ operator, then the boolean expression is a tautology, namely, the boolean expression is always true no matter the value $$\{0,1\}$$ that you assign to the variables.

If you were to use the definition of the logical operator $$\iff$$, it is probably not going to be very easy to prove the claim. But if you view the logical expression $$a \iff b$$ as $$a+b+1(mod2)$$, then the problem could be much easier. Namely, if you first change your boolean expression in the modular addition format and get rid of the parenthesis, you will get the sum of each variable an even number of times. The sum of the variable will therefore be equals to $$0(mod2)$$. Futhermore , each variable appear an even number of times means that there are an odd number of $$\iff$$ operators in the original boolean expression. When you converted the boolean expression into the expression involving sums of the variable + $$1$$, you essentially converted the odd number of $$\iff$$ operators into the sum of odd numbers of $$1$$'s plus the variables. We know that the sum of the variables is $$0(mod2)$$ and the sum of odd number of $$1$$'s is $$1(mod2)$$, therefore, the value of your converted expression is also $$1(mod2)$$. And since $$1$$ correspond to the boolean value True, you know that your expression is always true, hence a tautology.

Therefore, you see that this is a powerful technique of converting a boolean operator into arithmetic in mod2.

• This doesn't answer my question? I asked about the difference between $a \equiv b$ and $a \Longleftrightarrow b$, not $a \Longleftrightarrow b$ and $a + b + 1(mod2)$ – Raymo111 May 21 at 17:35
• I think they are equivalent. The symbol $\equiv$ is used in modular arithmetic as well. When you write $a \equiv b(modk)$, that means that $a,b$ have the same remainder after division by $k$. In the context of boolean algebra, each variable takes two values. If we think of them in mod2, then $a \equiv b(mod2)$ is true/fase if and only if $a \iff b$ is true/false. This is confirmed by the many comments that you got in your post as well. Given that stack exchange is a prestigious math discussion site, it is fun to learn a few extra :) – user614287 May 21 at 19:01


text:
# 1/7 in decimal form is .142857

1. Jan 12, 2005

### T@P

1/7 in decimal form is .142857
2/7 is a rearangement of those numbers, 3/7 is too etc. anyone know why? (btw 142857 is divible by 999)

2. Jan 12, 2005

### The Bob

$$\frac{1}{7} = 0. \dot1 4285 \dot7$$

$$\frac{2}{7} = 0.\dot2 8571 \dot4$$

$$\frac{3}{7} = 0.\dot4 2857 \dot1$$

$$\frac{4}{7} = 0.\dot5 7142\dot8$$

$$\frac{5}{7} = 0.\dot7 1428\dot5$$

$$\frac{6}{7} = 0.\dot8 5714\dot2$$

The pattern that I can see is that as the nominator increases the first number increases within the numbers there are. 1 then 2 then 4 then 5 etc... Also all the numbers stay in order. Why, though, I do not know.

Last edited: Jan 12, 2005
3. Jan 12, 2005

### dextercioby

Nope.1/7 is:
$$\frac{1}{7}=0.(142857)$$ (1)
,which is a totally different number from the one u've written.Yours is
$$0.142757=\frac{142857}{1000000}$$(2)
and has 6 decimals,while mine is
$$0.(142857)=\frac{142857}{999999}=\frac{1}{7}$$(3)
and has an infinite number of decimals.

What do u mean by rearrangement??

Daniel.
PS.From (3) u get
$$142857\cdot 7=999999=999\cdot 1001=999\cdot 7\cdot 11\cdot 13$$
,from which u get the decomposition of 142857 in prime factors.

4. Jan 13, 2005

### T@P

i meant rearangement of the first 6 digits, since they repeat you can think of it as 142857/999999, and incidentaly it reduces. actually i think that explains why its divisible by 999.

5. Jan 13, 2005

### NateTG

The same holds for any number $n$ which has the property that $\frac{1}{n}$ has $n-1$ repeating digits.
Here's what happens:
Code (Text):

1 = 1 mod 7
10 = 3 mod 7
100 = 2 mod 7
1000 = 6 mod 7
10000 = 4 mod 7
100000 = 5 mod 7

And, calculating the digits after the decimal point is very much like multiplying the denominator by 10, and calculating the last digit and a new remainder, so you cycle through the six possible remainders.

6. Jan 15, 2005

### robert Ihnot

NateTG has it pretty well figured out, but I never did see until now. By the way, they are called cyclic numbers and can be googled.

We have $$1/7 = \overline{.142857}$$. (Where the overline means the period is repeated and repeated)

The first decimal,1, represents how many times 7 goes into 10 whole , 14 represents how many times 7 goes whole into 100, 142 for 1000, etc.

Thus if we look at 100/7 = $$14\overline{.285714}$$

But 100/7 = 14 +2/7, so we end up with 2/7= $$\overline{.285714}$$

Thus as NateTG tells us to get the full array we need to have a cycle of N-1 digits, where 10^(N-1)==1 Mod N. This will only possibly occur when N = p, a prime.

For example, lets look at 1/21 = $$\overline{.047619}$$

The powers of 10^x modulo 21 are 1,10,16,13,4,19,1...for x=0,1,2,3,4,5,6...

i.e. 10^6 == 10^0==1 Modulo 21, and the series has finished.

Thus the cycle will repeat for some numbers, say, 16/21 = $$\overline{.761904}$$

But, of course, since there are only 6 possibilities, some numbers will not cycle that way, for example we have 2/21 = $$\overline{.095238}$$

Last edited: Jan 15, 2005


text:
# Problem #913

 913 The sum of two numbers is $S$. Suppose $3$ is added to each number and then each of the resulting numbers is doubled. What is the sum of the final two numbers? $\mathrm{(A)}\ 2S+3 \qquad\mathrm{(B)}\ 3S+2 \qquad\mathrm{(C)}\ 3S+6 \qquad\mathrm{(D)}\ 2S+6 \qquad\mathrm{(E)}\ 2S+12$ This problem is copyrighted by the American Mathematics Competitions.
Note: you aren't logged in. If you log in, we'll keep a record of which problems you've solved.


text:
Sciencemadness Discussion Board » Fundamentals » Chemistry in General » Preparation of cyanides Select A Forum Fundamentals   » Chemistry in General   » Organic Chemistry   » Reagents and Apparatus Acquisition   » Beginnings   » Responsible Practices   » Miscellaneous   » The Wiki Special topics   » Technochemistry   » Energetic Materials   » Biochemistry   » Radiochemistry   » Computational Models and Techniques   » Prepublication Non-chemistry   » Forum Matters   » Legal and Societal Issues

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Author: Subject: Preparation of cyanides
Pixicious
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It would be interesting to know how to make cyanohydrin.

If so that is a really interesting method because potash would be really easy for people to come by here.
Pixicious
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13 is unlucky, 14 is nice.

I'm not sure if you mean ethanol or methanol with the formula you mentioned.
Nicodem
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 Quote: Originally posted by Pixicious It would be interesting to know how to make cyanohydrin.

Acetone cyanohydrin is made by the reversed reaction (the reaction is catalysed by traces of KCN or any other base):
HCN + CH3COCH3 ---> (CH32C(OH)CN
I'm quite sure you can find the exact experimental in Vogel's, Organikum or any other book on laboratory practice.

PS: Try not to double post. Use the edit function instead.
grind
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The way via the cyanohydrine only makes sense, when you can buy the cyanohydrine. It´s cheap but very toxic and I think for most people hard to get.
Pixicious
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 Quote: 1) Where can we get strong ammonia solution

You mix NH4Cl (Ammonium Chloride) in water, this is not exothermic and then add NaOH (Sodium Hydroxide), this is exothermic.

If in the right quantites you will produce salt so there is no need to worry when you wash the solution away. The gas given off is NH3, feed this through water and you have a very concentrated NH4 solution.

NH4Cl + NaOH + H2O -> NH3 + 2H20 + NaCl
quicksilver
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 Quote: Originally posted by amchem2000 1) Where can we get strong ammonia solution

For absolute lowest cost I like ammonium sulfate (available at any garden supply, hardware store and sodium hydroxide (lye) via the above mechanism of gas generation through water. In terms of cost for either anhydrous ammonia gas or ammonia solution, you are actually dealing with pennies.
497
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I have a solution of an unknown amount of sodium cyanide with quite a bit of sodium carbonate and probably some sodium cyanate along with. I had the idea to add calcium hydroxide forming calcium carbonate precipitate. This should also produce calcium cyanide right? Then I read that calcium cyanide is unstable in water, so would I just get a bunch of HCN or what? There must be a better way to separate them.
Pixicious
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497: I don't know.

I just came here because from things I have been reading there is another way of producing NaCN from just household.

This method relies on Ammonia, Chloroform and Sodium Hydroxide producing Sodium Cyanide.

A couple of questions arrise. How are the three mixed together? NaOH + NH3(aq) cannot be in the same solution together, NaOH + CHCl3 -> NaCl + H2O + CCl3 and, NH3(aq) + CHCl3 is the only method I can think of mixing the two before dripping in the Sodium Hydroxide. Although I have a memory which says this produces HCN.

Is the reaction of Chloroform and Ammonia exothermic? If so is HCN, HCl or both released as a gas, or do either or both remain a liquid? I think this is an essential question for anybody here. Especially for purification.

The method involves just Ammonia, which is obtained by concentrating Ammonia solutions through heat into a much smaller amount of water. Calcium Carbonate which is used to produce Calcium Hydroxide, Sodium Hydroxide and Acetone. Also needed is Acetic Acid and Sodium Hypochlorite.

Obviously you will need to distill and dry at several points, and I am not sure where you can produce drying stuff from household. (Maximum temperture needed is: 850oC and that is only to produce Sodium Hydroxide.)

I would like to know if there is a known method of reacting Sodium Hypochlorite to form Calcium Hypochlorite power.

The seperation as described of HCl and HCN and an excess of NH3. (Just so all the chloroform has reacted) is to bring it to a boil of 26.5oC and bring a controlled release of HCN gas insealed containers feeding into a NaOH and methanol solution? Or in this case would the Hydrochloric acid not bound with the Hydrogen Cyanide and will be released as gas just leaving pure Hydrogen Cyanide..

[Edited on 9-4-2008 by Pixicious]
Pixicious
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If you bubble Ammonia through a solution of Hydrogen Cyanide and Hydrochloric Acid, would the Hydrochloric Acid (assuming it remains a solution in HCN) react to form Ammonium Chloride?

Then would it just be a simple case to filter the Ammonium Chloride from Hydrogen Cyanide to obtain a pure form of Hydrogen Cyanide.

Something I've been wanting to pick with you for a long time Polverone. If to achieve HCN all you have to do is slightly warm acidified Potassium Ferrocyanide, why is it not considered poisonious to ingest?

[Edited on 10-4-2008 by Pixicious]
Sauron
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Acetone cyanohydrin is easy. Yes the prep is in Vogel; he cadged it from Org.Syn as usual. See it there for more details and a larger scale.

I tried to order some from Aldrich and they wanted something like $2000 for ocean freight hazmat. So I got it from Merck. No hazmat which is entirely America shooting itself in the foot. I use it in one of the processes to prepare AIBN, the radical initiator for polymerizations and some chlorinations. Could have made my own but that would have meant making anhydrous HCN and better to work around that, than to work around it, if you get my meaning. Sic gorgeamus a los subjectatus nunc. 497 International Hazard Posts: 778 Registered: 6-10-2007 Member Is Offline Mood: HSbF6 I have heard mention of fusing calcium cyanamide with Na/KCO3 to yield the respective cyanide along with CaO and oxygen. If you can get/make CaCN2 easily this might be useful. Sorry I don't have more details, I'm way too busy with school to work on this. And sorry if this is old news, its been a while since I read this thread in detail. [Edited on 8-5-2008 by 497] Axt International Hazard Posts: 778 Registered: 28-1-2003 Member Is Offline Mood: No Mood NaCN via Nitrite + Acetate CH3COONa + NaNO2 --> [ONCH2COONa] --> NaCN + NaHCO3 + H2O See the attachment, in german so I cant make a lot of it out, would be good if someone can confirm what I've written here. By heating a mixture of 12g sodium acetate with 10g sodium nitrite with added bicarbonate (to stop or at least control the deflagration of the mixture) it gives NaCN in 25% yield. This isn't a lot, ~1.8g per 10g of nitrite. Gasseous HCN and H2O are released during the reaction. K nitrate + K acetate also forms some cyanide, presumably through the nitrite intermediate. Is the extraction of ther NaCN mentioned in the article? How was it analysed to determine 25%? It says something about 70% alcohol but I cant make it out. Maybe its possible to increase the yield by trapping the lost HCN via NaOH/EtOH, though I suspect this will also have a bicarbonate impurity. Attachment: nitrite-cyanide ocr.pdf (97kB) This file has been downloaded 1135 times Formatik International Hazard Posts: 927 Registered: 25-3-2008 Member Is Offline Mood: equilibrium In this process without the soda they had a violent explosion from it (I'm not sure what the source of explosion is, if it is the possible reaction as an oxidizer mixture or HCN as according to Urbanski hydrogen cyanide is explosive, and alkalinity can polymerize it explosively). The procedure they give they say it occurs without explosion. The proportion of soda needs to be as described, already 3g of mixture and 2 g soda ratio deflagrates pretty vigorously. Though a 1:1 mass ratio in a metal bath starts to soften and inflate around 300 deg., at 375 deg. water and significant amounts of HCN is let free under fizzling and freezes to a porous mixture of carbonic acid salt and NaCN. 12 g sodium acetate and 10 g NaNO2 with 22 g soda (Na2CO3) in a porcellain crucible is heated over a free flame. This will soften and glow, as soon as the reaction temperature is reached, there is a lively glimmering, but it occurs without explosion or spattering, whereas water and noticeable amounts of hydrogen cyanide escape. The porous, crumbling mass is colored dark from the separated coal. By boiling with 70% pure alcohol the NaCN can be extracted and then after a repeated recrystallization by cooling an aqueous-alcoholic solution, can the plates as described by Joannis be obtained. They did the determination of yield by precipitating AgCN from the NaCN, and then weighed it. The yield of NaCN is dependent on the type of heating, and from that no more than 25% yield results. Note: NaHCO3 will lose mass (37% mass) as it is heated at low to moderate temperatures forming H2O and CO2. Na2CO3 forms several hydrates and will also lose mass. Both of these might skew the ratio unfavorably. Also reading further the explosion source is likley a redox reaction maybe going through unstable intermediates, as NaNO2 reacts similarily with sodium formate, propionate, or tartrate, also forming more or less NaCN. [Edited on 7-6-2008 by Schockwave] Ephoton National Hazard Posts: 463 Registered: 21-7-2005 Member Is Offline Mood: trying to figure out why I need a dark room retreat when I live in a forest of wattle. an idea if one was to go from sodium or potassium cyanate then any reducing agent that works in the conversion of nitrates too nitrites should work. there was a post in this forum some were from a gentleman from the upper block of europe stating it was impossible to get nitrites in his area. he stated that the general way to obtain these was to heat the nitrate untill it was molten then add lead tartrate. after a bit of thought and some looking around and a few small tests this would seem to me to be the best way to make very pure cyanide as well. I would expect any problems found in the conversion of one would also be seen in the conversion of the other (ie nitrate or cyanate) by the way thanx KMnO4 for the hint it was a true killer just as I thought to be honest it will stay at the amide. and thanx Nicodem for posting the entire article. [Edited on 9-6-2008 by Ephoton] e3500 console login: root bash-2.05# Axt International Hazard Posts: 778 Registered: 28-1-2003 Member Is Offline Mood: No Mood Thanks for the translation Schockwave, this may be the explanation for its explosive nature. The double salt, KCN.KNO2.H2O, is obtained by dissolving potassium nitrite (50 grams) aiid potassium cyanide (20 grams) in the smallest possible quantity of water and allowing the solution to evaporate over sulphuric acid. Potassium cyanide separates first, and then the new double salt in short, characteristic prisms. It explodes with a loud report when heated at 400-500°. J. Chem. Soc., Abstr. 70, I, 69 1896. [Edited on 14-6-2008 by Axt] jarynth Hazard to Self Posts: 76 Registered: 12-8-2008 Member Is Offline Mood: No Mood Cyanide manufacture Gary R. Maxwell's Synthetic Nitrogen Products (Kluwer) offers a quick survey of the industrial syntheses of basic nitrogen compounds. Chapter 19 is dedicated to hydrogen cyanide. I won't even mention the high pressure gas phase processes, but the following could be useful in an amateur setting, provided the necessary precaution is met. 1) 'The dehydration of formamide is conducted in iron catalyst at 380°C to 430°C under reduced pressure. The tubes are filed with Fe or Al phosphate catalyst that also contains Mg, Ca, Zn or Mn as promoters. The selectivity to HCN is 92% to 95%' (Weissermehl, Arpe Industrial organic chemistry VCH 1997) 2) It's a common oppinion that this organic compound cannot be turned appreciably into ionic cyanides; luckily this is true as far as the human metabolism goes, but the Japanese patent 10167721 makes a refreshing claim. For those who can find acetonitrile cheaply, and with a tube furnace, consider this: 'PROBLEM TO BE SOLVED: To efficiently convert acetonitrile into prussic acid by a simple method by using activated carbon as a catalyst in producing prussic acid by reacting acetonitrile with oxygen or oxygen and ammonia. SOLUTION: In this method for producing prussic acid by effectively utilizing acetonitrile as a by-product in production of acrylonitrile, activated carbon is used as a catalyst. Industrially useful activated carbon is generally used. The shape of activated carbon may be granule of powder. Pure acetonitrile is not necessarily required and a mixture may be used. Oxygen may be diluted with an inert gas such as nitrogen or may be supplied as air. The amount of oxygen used is preferably 2-3 mols based on 1mol of acetonitrile. The reaction temperature is preferably 400-500 deg.C. The reaction pressure is preferably high with respect to contact efficiency with the catalyst and may be normal pressure or slightly under pressure in terms of simplicity of facilities. The reaction time is preferably about 0.5-5 seconds.' len2 Harmless Posts: 32 Registered: 13-9-2008 Member Is Offline Mood: No Mood Someone on the forum was interested in this so I tried it out.  Quote: Decomposition of Potassium Ferricyanide by the Action of Heat. V. CUTTICA (Guzsetta, 1922, 52, i, 20-.25).- Protracted heating of potassium ferricyanide at 230C results in complete decomposition of the salt according to the equation 2K3Fe(CN)6 = 2FeC2 + 2N2 + CN2 + 6KCN. 658 56 52 390 The intermediate green substance formed during the heating (cf. Locke and Edwards, A., 1899, i, 407, 557; Cuttica and Canneri, A., 1921, i, 322) exhibits the oxidising properties of the original salt, but differs from it in certain of its reactions, and contains complex iron cyanides with less than six cyanogen groups in the molecule. Ferricyanide is superior to the ferro salt in that there is no water of crystalization (.3H2O for ferro) to speak off. But at 230C there was almost no weight loss as per formula - and there was only 0.1gms lost at 480C for up to two hours heating. This puts in doubt the report above if it refers to anything like reasonable reaction time, as chemical reaction rates on average double every 10C or so. Nonetheless some iron was reduced as addition of HCl resulted in deep blue colouration indicating some Fe(II) present (the original ferricyanide gives a deep yellow colouration only). 4.4gms ferricyanide was then held at 180C for 1hr in a box oven to rid of any moisture, then heat was raised to 400C for 0.5hrs, 640C 2hrs, 680C 0.5hr. A borosilicate tube blocked with glass wool was used as container - which was not ideal as it softened and bent, while KCN being basic attacks the glass. Nonetheless at the end the bent tube was filled with a white powder and black granules, was brocken, ground up, and 50ml H2O added and mixed. Filtration under vacuum gave a clear solution (no ferri evident in product). This shouldnt be evaporated as KCN decomposes in boiling water. Alcohol added (100ml) immediately gave a white precipitate which was filtered and dried. 1gm obtained, which = 40% yield - would be higher for larger batches. To test for KCNO 0.1gms was dissolved in H2O/alcohol and HCl (conc) added. A heavy mist of HCN resulted, but there was no effervescense (CO2) - this quick test indicates no substantial oxidation of KCN had occurred. [Edited on 22-2-2009 by len2] densest National Hazard Posts: 359 Registered: 1-10-2005 Location: in the lehr Member Is Offline Mood: slowly warming to strain point One approach which I saw appeared to work: To a cold saturated solution of KOH was added K4Fe(CN)6 crystals until no more would dissolve. The flask was sealed with plastic film to exclude CO2 and O2. Over a period of some days, Fe hydroxides and oxides precipitated, and the color of the solution changed from yellow-green to clear. The supernatant was decanted. On further chilling, transparent square plates and small cubes crystallized. Filtered quickly, washed with a minimum of very cold distilled water, a very small amount (milligrams) gave a very strong blue reaction with FeSO4 solution. I believe it took several weeks overall, using an outdoor shed during autumn. It would seem to depend on KCN being somewhat less soluble than KOH or K2CO3 and very little O2 being available to destroy the KCN. Perhaps the air in the flask could be displaced with something else to improve the yield. According to an old Chem Rubber handbook, the only likely substance in that solution which crystallizes to a square or cubic form would be KCN giving a second reason to believe the process worked. S.C. Wack bibliomaster Posts: 2419 Registered: 7-5-2004 Location: Cornworld, Central USA Member Is Offline Mood: Enhanced I'm sure people will be giving that a try now. ---- There are many places where one can find a mini-review of cyanide, and many resources have been posted on this board over the years. At the very beginning, Beilstein mentions a review in JACS http://books.google.com/books?id=lAkSAAAAIAAJ&pg=PA31 there is also http://books.google.com/books?id=lAkSAAAAIAAJ&pg=PA3 These are not the greatest, but they are informative to those not aware of the history (to 1889) and it gives me something to post. If anyone is interested in looking up old things probably in a different language, since I have these old photocopies and they're just gathering dust and personally I like it when people post things such as Beilstein, 14 pages from the Hauptwerk on preparation/formation/occurrence of HCN, the complete entries for NH4CN, NaCN, K4Fe(CN)6, K3Fe(CN)6, and most of KCN. Attachment: beilstein_cn.pdf (1.7MB) This file has been downloaded 1856 times len1 International Hazard Posts: 595 Registered: 1-3-2007 Member Is Offline Mood: NZ 1 (goal) - Italy 1 (dive) Thanks for the info SC Wack. But none of the links work. The first two only give me the title pages the last hangs the computer. ANYONE WHO WORKS WITH CYANIDES INCLUDING MYSELF MUST WEAR A GAS MASK, GLOVES and GLASSES!. Even in this case when theoretically no HCN is generated KCN spilled on a stray drop of HCl, can generate enough HCN to kill, especially if you are like myself and cant smell it. Grinding or picking KCN can stray particles into your face and mouth - also enough to kill. A mask will guard against all of this. Gloves give protection against KCN dissolving in skin moisture and penetrating though cuts etc. Glasses protect against KCN particles flicked into the eye dissolving in tears, being absorbed, and killing. Symptoms of mild CN poisoning resemble symptoms of fear of having been poisoned (anxiety). Ive done the Ksp calculations, and the KOH method must work and it must work even better with K3FeCN6 since its last cyanide is weakly bound (making it poisnous) so that it can be substantially separated even in boiling water [Fe(CN)6]3- + OH- -> [Fe(CN)5OH]3- + CN-; [Fe(CN)6]3- + H2O -> [Fe(CN)5H2O]2- + CN- Removal of all the cyanides if you check the K's proceeds because of the low Ksp of iron hydroxide. BUT its all very slow and inefficient. In practice my method is better: simplest method imaginable - no mixing, weighing etc; takes a few hrs; directly gives pure KCN; is safe for non-specialist labs - no HCN at any stage Yiled can be improved, but at the expense of a lot more dangerous work. At this level I think this method is perfect. [Edited on 24-2-2009 by len1] S.C. Wack bibliomaster Posts: 2419 Registered: 7-5-2004 Location: Cornworld, Central USA Member Is Offline Mood: Enhanced  Quote: Originally posted by len1 Thanks for the info SC Wack. But none of the links work. The first two only give me the title pages the last hangs the computer As I told Sauron to some argumentation last week, the Google links work perfectly for those in certain countries, like the USA, however Polverone deleted my explanation on how others can get around this so I ought not post it again. Nor is there anything wrong with the pdf, I'm always the first one to download to make sure it works and it just worked again. All attachment downloads in the past few months stop at say 98% for 10 seconds then finish. Maybe its a virus scanning thing or something, or just a problem, in any case that's the way it is and they always finish for me. [Edited on 24-2-2009 by S.C. Wack] not_important International Hazard Posts: 3873 Registered: 21-7-2006 Member Is Offline Mood: No Mood For me the attached PDF stalled closer to 20 seconds, but did finish and yield a readable file. The Google links work when accessed through a proxy in the U.S. It is amusing to read  Quote: In 1837 Neilson first introduced the use of the hot blast at the Clyde iron furnaces. Shortly afterwards,1 a peculiar exudation of fused salt which hardened on reaching the air to a white, opaque mass was noticed upon the walls of the furnace near the boshes. The substance was regarded with much curiosity and it is related by Clark, who made the first analysis of the product, that its alkaline character was soon discovered by the workman and that it was used by the wife of one of them, for a time, as a substitute for soap in washing clothes.2 Clark's analysis allowed it to contain potassium cyanide 43.4%, potassium carbonate 45.8%. No ferrocyanide was present. len1 International Hazard Posts: 595 Registered: 1-3-2007 Member Is Offline Mood: NZ 1 (goal) - Italy 1 (dive)  Quote: Originally posted by not_important it was used by the wife of one of them, for a time, as a substitute for soap in washing clothes.2 I guess it was a very short time ... A useful thing I found when working with cyanides is to have a developing solution - a few specks of FeCl3 (PCB etchant) and a few specs of FeSO4 (garden fertilizer) dissolved in 10ml H2O, dab it around the lab to locate specs of KCN which might have been left lying around. Even traces of KCN give an intense blue colouration (as of course would ferro/ferri cyanides) Magpie lab constructor Posts: 5939 Registered: 1-11-2003 Location: USA Member Is Offline Mood: Chemistry: the subtle science. len1, there is the Liebig method for the determination of cyanide. This may be of help in your optimization. I've extracted this from "Quantitative Analysis," 3rd Ed, 1951, p.305, by Pierce & Haenisch, as follows: "Procedure. To the dissolved sample (note 1) which should contain 6-8 mmol of cyanide ion, add 30-40 mmol of ammonium hydroxide and 0.1-0.2 g potassium iodide, and dilute to a volume of 100 ml. Titrate with standard 0.1M silver nitrate until the addition of 1 drop of reagent causes the appearance of a permanent turbidity in the solution (note 2). Notes. 1. Keep constantly in mind the very poisonous nature of potassium cyanide. Be sure to wash out the solution with a large quantity of water at the conclusion of the determination. Do not allow any waste cyanide to stand in a sink where it may come in contact with acids and evolve hydrogen cyanide gas." The reaction up to the endpoint is: Ag+ + 2CN- ----> [Ag(CN)2]- So, for every mole of Ag+ consumed there was 2 moles of cyanide present. len2 Harmless Posts: 32 Registered: 13-9-2008 Member Is Offline Mood: No Mood Thanks Magpie. One thing i was trying to avoid is using silver - why is it so popular in titrations of CN? Its$55/10gms. So for 8mmol a sinle titration is \$2.40! The other thing is AgCNO is also insoluble. Is there any statement to the effect of cyanates? I suppose i could make some cyanate and see.

[Edited on 26-2-2009 by len2]
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# User:Sebastian Hudak

🏠 User page 💬 Talk 🖨 Contribs

My name is Sebastian Hudak, and I'm a young hobbyist software developer and privacy/freedom advocate. The Wikimedia Foundation's mission to ensure that all knowledge is free (as in free speech and as in free beer) is very important to me, and as such I'll attempt to contribute as much as possible to any Wikipedias possible.

All stuff that I work on personally should be on my website. I host a (very inactive) blog there as well.

I love chatting with others, regardless of the topic. If you want to chat for whatever reason, talk to me on my talk page! I'd love to chat!

"Living is easy with eyes closed, misunderstanding all you see." – John Lennon

## Potential Biases

When editing, I try to be as unbiased and neutral as possible. However, like everyone else, I am vulnerable to bias. As such, I will put information about myself and my beliefs here so other users can call me out in the event that I show some implicit bias. The intent of this isn't to begin an argument, though I do enjoy civil debate. Please do not harass me.

• I am Caucasian/white, but a strong supporter of racial equality. The only reason racism exists is because human brains haven't evolved much from those of hunter-gatherers from the Paleolithic era.
• I was born as and identify as male, but I am a strong supporter of gender equality, transsexual rights, and non-binary acceptance.
• I was born and currently live in the United States, although to be honest I've grown a distaste for my country. I'm a patriot in the sense that I want my nation to be the best it can be, and I dislike my nation in its current state because things are fundamentally wrong. Of course, I want every nation to be the best it can be, but I primarily focus on local and national politics as it's what effects me the most.
• I am an atheist. Religion doesn't dictate my morals. Although religion can be and is used to justify horrible things, I don't believe religion is evil. Most religions are built on the ideas of peace. If people use religion to guide them and develop good morals, power to them. I do however believe that religion is an old way of attempting to explain many unexplainable questions about humanity, our world, and our universe. A lot of that stuff is now outdated.
• On the political compass, I identify as being slightly above the middle of the lib-left quadrant, though tests online suggest that I'm either right in the middle or further left/down. Abstract political scales such as the political compass do a poor job of representing political beliefs, because politics is too complicated for such a visualization/metaphor to work. Instead, when discussing politics, it makes more sense to pinpoint your stance on particular issues (though I won't do that here, because that would be too long). On the traditional U.S. one dimensional scale, I'm generally left-wing (progressive) on most issues.
• I am heterosexual, but a strong supporter of LGBT rights and acceptance.
• I am extremely tech-savvy, and most of my work/hobbies involve computers, technology, and coding. I almost exclusively use free software, and I'm a big advocate for digital privacy, which most people seem okay with giving up. (Donate to EFF by the way!)
• I am a minor. Currently, I am 17 years old and a junior (11th grader) in high school.
• I am a vegetarian, though I eventually want to become vegan. The cruelty to animals that is normalized in our society disgusts me.


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## 22.1 Dropping Proportionality Constants

If a density $$p(\theta)$$ can be factored into $$K g(\theta)$$ where $$K$$ are all the factors that are a not a function of $$\theta$$ and $$g(\theta)$$ are all the terms that are a function of $$\theta$$, then it is said that $$g(\theta)$$ is proportional to $$p(\theta)$$ up to a constant.

The advantage of all this is that sometimes $$K$$ is expensive to compute and if it is not a function of the distribution that is to be sampled (or optimized or approximated with variational inference), there is no need to compute it because it will not affect the results.

Stan takes advantage of the proportionality constant fact with the ~ syntax. Take for instance the normal likelihood:

data {
real mu;
real<lower=0.0> sigma;
}
parameters {
real x;
}
model {
x ~ normal(mu, sigma);
}

Syntactically, this is just shorthand for the equivalent model that replaces the ~ syntax with a target += statement and a normal_lupdf function call:

data {
real mu;
real<lower=0.0> sigma;
}
parameters {
real x;
}
model {
target += normal_lupdf(x | mu, sigma)
}

The function normal_lupdf is only guaranteed to return the log density of the normal distribution up to a proportionality constant density to be sampled. The proportionality constant itself is not defined. The full log density of the statement here is:

$\textsf{normal\_lpdf}(x | \mu, \sigma) = -\log \left( \sigma \sqrt{2 \pi} \right) -\frac{1}{2} \left( \frac{x - \mu}{\sigma} \right)^2$

Now because the density here is only a function of $$x$$, the additive terms in the log density that are not a function of $$x$$ can be dropped. In this case it is enough to know only the quadratic term:

$\textsf{normal\_lupdf}(x | \mu, \sigma) = -\frac{1}{2} \left( \frac{x - \mu}{\sigma} \right)^2$