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Earlier this week US News and World Report (USNWR) released, for the first time, a global ranking of universities including rankings by subject area. In mathematics, the top ten universities are:

1. Berkeley
2. Stanford
3. Princeton
4. UCLA
5. University of Oxford
6. Harvard
7. King Abdulaziz University
8. Pierre and Marie Curie – Paris 6
9. University of Hong Kong
10. University of Cambridge

The past few days I’ve received a lot of email from colleagues and administrators about this ranking, and also the overall global ranking of USNWR in which Berkeley was #1. The emails generally say something to the effect of “of course rankings are not perfect, everybody knows… but look, we are amazing!”

BUT, one of the top math departments in the world, the math department at the Massachusetts Institute of Technology is ranked #11… they didn’t even make the top ten. Even more surprising is the entry at #7 that I have boldfaced: the math department at King Abdulaziz University (KAU) in Jeddah, Saudi Arabia. I’ve been in the math department at Berkeley for 15 years, and during this entire time I’ve never (to my knowledge) met a person from their math department and I don’t recall seeing a job application from any of their graduates… I honestly had never heard of the university in any scientific context. I’ve heard plenty about KAUST (the King Abdullah University of Science and Technology ) during the past few years, especially because it is the first mixed-gender university campus in Saudi Arabia, is developing a robust research program based on serious faculty hires from overseas, and in a high profile move hired former Caltech president Jean-Lou Chameau to run the school. But KAU is not KAUST.

A quick google searched reveals that although KAU is nearby in Jeddah, it is a very different type of institution. It has two separate campuses for men and women. Although it was established in 1967 (Osama Bin Laden was a student there in 1975) its math department started a Ph.D. program only two years ago. According to the math department website, the chair of the department, Prof. Abdullah Mathker Alotaibi, is a 2005 Ph.D. with zero publications [Update: Nov. 10: This initial claim was based on a Google Scholar Search of his full name; a reader commented below that he has published and that this claim was incorrect. Nevertheless, I do not believe it in any way materially affect the points made in this post.] This department beat MIT math in the USNWR global rankings! Seriously?

The USNWR rankings are based on 8 attributes:

– global research reputation
– regional research reputation
– publications
– normalized citation impact
– total citations
– number of highly cited papers
– percentage of highly cited papers
– international collaboration

Although KAU’s full time faculty are not very highly cited, it has amassed a large adjunct faculty that helped them greatly in these categories. In fact, in “normalized citation impact” KAU’s math department is the top ranked in the world. This amazing statistic is due to the fact that KAU employs (as adjunct faculty) more than a quarter of the highly cited mathematicians at Thomson Reuters. How did a single university assemble a group with such a large proportion of the world’s prolific (according to Thomson Reuters) mathematicians? (When I first heard this statistic from Iddo Friedberg via Twitter I didn’t believe it and had to go compute it myself from the data on the website. I guess I believe it now but I still can’t believe it!!)

In 2011 Yudhijit Bhattacharjee published an article in Science titled “Saudi Universities Offer Cash in Exchange for Academic Prestige” that describes how KAU is targeting highly cited professors for adjunct faculty positions. According to the article, professors are hired as adjunct professors at KAU for \$72,000 per year in return for agreeing (apparently by contract) to add KAU as a secondary affiliation at ISIhighlycited.com and for adding KAU as an affiliation on their published papers. Annual visits to KAU are apparently also part of the “deal” although it is unclear from the Science article whether these actually happen regularly or not.

[UPDATE Oct 31, 12:14pm: A friend who was solicited by KAU sent me the invitation email with the contract that KAU sends to potential “Distinguished Adjunct Professors”. The details are exactly as described in the Bhattacharjee article:

```From: "Dr. Mansour Almazroui" <ceccr@kau.edu.sa>
Date: XXXX
To: XXXX <XXXX>
Subject: Re: Invitation to Join “International Affiliation Program” at
King Abdulaziz University, Jeddah Saudi Arabia

Dear Prof. XXXX ,

Hope this email finds you in good health. Thank you for your interest.
Please find below the information you requested to be a

1. Joining our program will put you on an annual contract initially
for one year but further renewable. However, either party can
terminate its association with one month prior notice.
2. The Salary per month is \$ 6000 for the period of contract.
3. You will be required to work at KAU premises for three weeks in
each contract year. For this you will be accorded with expected
three visits to KAU.
4. Each visit will be at least for one week long but extendable as
suited for research needs.
5. Air tickets entitlement will be in Business-class and stay in Jeddah
will be in a five star hotel. The KAU will cover all travel and living
6. You have to collaborate with KAU local researchers to work on KAU
funded (up to \$100,000.00) projects.
7. It is highly recommended to work with KAU researchers to submit an
external funded project by different agencies in Saudi Arabia.
8. May submit an international patent.
9. It is expected to publish some papers in ISI journals with KAU
affiliation.
10. You will be required to amend your ISI highly cited affiliation
details at the ISI
highlycited.com
web site to include your employment and affiliation with KAU.

Kindly let me know your acceptance so that the official contract may
be preceded.

Sincerely,

Mansour```

]

The publication of the Science article elicited a strong rebuttal from KAU on the comments section, where it was vociferously argued that the hiring of distinguished foreign scholars was aimed at creating legitimate research collaborations, and was not merely a gimmick for increasing citation counts. Moreover, some of the faculty who had signed on defended the decision in the article. For example, Neil Robertson, a distinguished graph theorist (of Robertson-Seymour graph minors fame) explained that “it’s just capitalism,” and “they have the capital and they want to build something out of it.” He added that “visibility is very important to them, but they also want to start a Ph.D. program in mathematics,” (they did do that in 2012) and he added that he felt that “this might be a breath of fresh air in a closed society.” It is interesting to note that despite his initial enthusiasm and optimism, Professor Robertson is no longer associated with KAU.

In light of the high math ranking of KAU in the current USNWR I decided to take a closer look at who KAU has been hiring, why, and for what purpose, i.e. I decided to conduct post-publication peer review of the Bhattacharjee Science paper. A web page at KAU lists current “Distinguished Scientists” and another page lists “Former Distinguished Adjunct Professors“. One immediate observation is that out of 118 names on these pages there is 1 woman (Cheryl Praeger from the University of Western Australia). Given that KAU has two separate campuses for men and women, it is perhaps not surprising that women are not rushing to sign on, and perhaps KAU is also not rushing to invite them (I don’t have any information one way or another, but the underrepresentation seems significant). Aside from these faculty, there is also a program aptly named the “Highly Cited Researcher Program” that is part of the Center for Excellence in Genomic Medicine Research. Fourteen faculty are listed there (all men, zero women). But guided by the Science article which described the contract requirement that researchers add KAU to their ISI affiliation, I checked for adjunct KAU faculty at Thomson-Reuters ResearcherID.com and there I found what appears to be the definitive list.

Another, bigger, disgrace that emerged in my examination of the KAU adjunct faculty is the issue of women. Aside from the complete lack of women in the “Highly Cited Researcher Program”, I found that most of the genomics adjunct faculty hired via the program will be attending an all-male conference in three weeks. The “Third International Conference on Genomic Medicine” will be held from November 17–20th at KAU. This conference has zero women. The same meeting last year… had zero women. I cannot understand how in 2014, at a time when many are speaking out strongly about the urgency of supporting females in STEM and in particular about balancing meetings, a bunch of men are willing to forgo all considerations of gender equality for the price of ~\$3 per citation per year (a rough calculation using the figure of \$72,000 per year from the Bhattacharjee paper and 24,000 citations for a highly cited researcher). To be clear I have no personal knowledge about whether the people I’ve mentioned in this article are actually being paid or how much, but even if they are being paid zero it is not ok to participate in such meetings. Maybe once (you didn’t know what you are getting into), but twice?!

As for KAU, it seems clear based on the name of the “Highly Cited Researcher Program” and the fact that they advertise their rankings that they are specifically targeting highly cited researchers much more for their delivery of their citations than for development of genuine collaborations (looking at the adjunct faculty I failed to see any theme or concentration of people in any single area as would be expected in building a coherent research program). However I do not fault KAU for the goal of increasing the ranking of their institution. I can see an argument for deliberately increasing rankings in order to attract better students, which in turn can attract faculty. I do think that three years after the publication of the Science article, it is worth taking a closer look at the effects of the program (rankings have increased considerably but it is not clear that research output from individuals based at KAU has increased), and whether this is indeed the most effective way to use money to improve the quality of research institutions. The existence of KAUST lends credence to the idea that the king of Saudi Arabia is genuinely interested in developing Science in the country, and there is a legitimate research question as to how to do so with the existing resources and infrastructure. Regardless of how things ought to be done, the current KAU emphasis on rankings is a reflection of the rankings, which USNWR has jumped into with its latest worldwide ranking. The story of KAU is just evidence of a bad problem getting worse. I have previously thought about the bad version of the problem:

A few years ago I wrote a short paper with my (now former) student Peter Huggins on university rankings:

P. Huggins and L.P., Selecting universities: personal preferences and rankings, arXiv, 2008.

It exists only as an arXiv preprint as we never found a suitable venue for publication (this is code for the paper was rejected upon peer review; no one seemed interested in finding out the extent to which the data behind rankings can produce a multitude of stories). The article addresses a simple question: given that various attributes have been measured for a bunch of universities, and assuming they are combined (linearly) into a score used to produce rankings, how do the rankings depend on the weightings of the individual attributes? The mathematics is that of polyhedral geometry, where the problem is to compute a normal fan of a polytope whose vertices encode all the possible rankings that can be obtained for all possible weightings of the attributes (an object we called the unitope). An example is shown below, indicating the possible rankings as determined by weightings chosen among three attributes measured by USNWR (freshman retention, selectivity, peer assessment). It is important to keep in mind this is data from 2007-2008.

Our paper had an obvious but important message: rankings can be very sensitive to the attribute weightings. Of course some schools such as Harvard came out on top regardless of attribute preferences, but some schools, even top ranked schools, could shift by over 50 positions. Our conclusion was that although the data collected by USNWR was useful, the specific weighting chosen and the ranking it produced were not. Worse than that, sticking to a single choice of weightings was misleading at best, dangerous at worse.

I was reminded of this paper when looking at the math department rankings just published by USNWR. When I saw that KAU was #7 I was immediately suspicious, and even Berkeley’s #1 position bothered me (even though I am a faculty member in the department). I immediately guessed that they must have weighted citations heavily, because our math department has applied math faculty, and KAU has their “highly cited researcher program”. Averaging citations across faculty from different (math) disciplines is inherently unfair. In the case of Berkeley, my applied math colleague James Sethian has a paper on level set methods with more than 10,000 (Google Scholar) citations. This reflects the importance and advance of the paper, but also the huge field of users of the method (many, if not most, of the disciplines in engineering). On the other hand, my topology colleague Ian Agol’s most cited paper has just over 200 citations. This is very respectable for a mathematics paper, but even so it doesn’t come close to reflecting his true stature in the field, namely the person who settled the Virtually Haken Conjecture thereby completing a long standing program of William Thurston that resulted in many of the central open problems in mathematics (Thurston was also incidentally an adjunct faculty member at KAU for some time). In other words, not only are citations not everything, they can also be not anything. By comparing citations across math departments that are diverse to very differing degrees USNWR rendered the math ranking meaningless. Some of the other data collected, e.g. reputation, may be useful or relevant to some, and for completeness I’m including it with this post (here) in a form that allows for it to be examined properly (USNWR does not release it in the form of a table, but rather piecemeal within individual html pages on their site), but collating the data for each university into one number is problematic. In my paper with Peter Huggins we show both how to evaluate the sensitivity of rankings to weightings and also how to infer bounds on the weightings by USNWR from the rankings. It would be great if USNWR included the ability to perform such computations with their data directly on their website but there is a reason USNWR focuses on citations.

The impact factor of a journal is a measure of the average amount of citation per article. It is computed by averaging the citations over all articles published during the preceding two years, and its advertisement by journals reflects a publishing business model where demand for the journal comes from the impact factor, profit from free peer reviewing, and sales from closed subscription based access.  Everyone knows the peer review system is broken, but it’s difficult to break free of when incentives are aligned to maintain it. Moreover, it leads to perverse focus of academic departments on the journals their faculty are publishing in and the citations they accumulate. Rankings such as those by USNWR reflect the emphasis on citations that originates with the journals, as so one cannot fault USNWR for including it as a factor and weighting it highly in their rankings. Having said that, USNWR should have known better than to publish the KAU math rankings; in fact it appears their publication might be a bug. The math department rankings are the only rankings that appear for KAU. They have been ommitted entirely from the global overall ranking and other departmental rankings (I wonder if this is because USNWR knows about the adjunct faculty purchase). In any case, the citation frenzy feeds departments that in aggregate form universities. Universities such as King Abdulaziz, that may reach the point where they feel compelled to enter into the market of citations to increase their overall profile…

I hope this post frightened you. It should. Happy Halloween!

[Update: Dec. 6: an article about KAU and citations has appeared in the Daily Cal, Jonathan Eisen posted his exchanges with KAU, and he has storified the tweets]

The Genotype-Tissue Expression (GTEx) project is an NIH initiative to catalog human tissue-specific expression patterns in order to better understand gene regulation (see initial press release). The project is an RNA-Seq tour-de-force: RNA extracted from multiple tissues from more than 900 individuals is been quantified with more than 1,800 RNA-Seq experiments. An initial paper describing the experiments was published in Nature Genetics earlier this year and the full dataset is currently being analyzed by a large consortium of scientists.

I have been thinking recently about how to analyze genotype-tissue expression data, and have been looking forward to testing some ideas. But I have not yet become involved directly with the data, and in fact have not even submitted a request to analyze it. Given the number of samples, I’d been hoping that some basic mapping/quantification had already been done so that I could build on the work of the consortium. But, alas, this past week I got some bad news.

In a recent twitter conversation, I discovered that the program that is being used by several key GTEx consortium members to quantify the data is Flux Capacitor developed by Michael Sammeth while he was in Roderic Guigós group at the CRG in Barcelona.

What is Flux Capacitor?

Strangely, the method has never been published, despite the fact that it has been used in ten publications over the course of four years, including high profile papers from consortia such as ENCODE, GENCODE, GEUVADIS and GTEx. There is no manuscript on the author’s website or in a preprint archive. There is a website for the program but it is incomplete and unfinished, and contains no coherent explanation of what the program does. Papers using the method point to the article S. B. Montgomery, … , E. T. DermitzakisTranscriptome genetics using second generation sequencing in a Caucasian population, Nature 464 (2010) and/or the website http://sammeth.net/confluence/display/FLUX/Home for a description of the method. Here is what these citations amount to:

The Montgomery et al. paper contains one figure providing the “FluxCapacitor outline”. It is completely useless in actually providing insight into what Flux Capacitor does:

Modification of the top half of Supplementary Figure 23 from Montgomery et al (2010) titled “Flux Capacitor Outline” (although it actually shows a splice graph if one corrects the errors as I have done in red).

The methods description in the Online Methods of Montgomery et al. can only be (politely) described as word salad. Consider for example the sentence:

In our approach we estimate the biases characteristic of each experiment by collecting read distribution profiles in non-overlapping transcripts, binned by several transcript lengths and expression levels. From these profiles, we estimate for each edge and transcript a flux correction factor $b^j_i$ that following the language of hydro-dynamic flow networks, we denote as the capacity of the edge, as the area under the transcript profile between the edge boundaries (Supplementary Fig. 23).

The indices and j for $b^j_i$ are never defined, but more importantly its completely unclear what the the correction factor actually is, how it is estimated, and how it is used (this should be compared to the current sophistication of other methods). On the program website there is no coherent information either. Here is an example:

The resulting graph with edges labelled by the number of reads can be interpreted as a flow network where each transcript representing a transportation path from its start to its end and consequently each edge a possibly shared segment of transportation along which a certain number of reads per nucleotide — i.e., a flux — is observed.

I downloaded the code and it is undocumented- even to the extent that it is not clear what the input needs to be or what the output means. There is no example provided with the software to test the program.

I therefore became curious why GTEx chose Flux Capacitor instead of many other freely available tools for RNA-Seq (e.g. ALEXA-SeqCLIIQCufflinks, eXpress, iReckon IsoEM, IsoformExMISO, NEUMARSEM, rSEQrQuantSLIDE, TIGAR, …). Although many of these programs are not suitable for production-scale analysis, Cufflinks and RSEM certainly are, and eXpress was specifically designed for efficient quantification (linear in the number of mapped reads and constant memory). I looked around and no benchmark of Flux Capacitor has ever been performed–there is literally not even a mention of it in any paper other than in manuscripts by Sammeth, Guigó or Dermitzakis. So I thought that after four years of repeated use of the program in high profile projects, I would take a look for myself:

After fumbling about with the barely usable Flux Capacitor software, I finally managed to run it on simulated data generated for my paper: Adam Roberts and Lior Pachter, Streaming fragment assignment for real time analysis of sequencing experiments, Nature Methods 10 (2013), 71–73. One example of the state of the software is the example page (the required sorted file is posted there but its download requires the realization that is is linked to from the non-obviously placed paperclip). Fortunately, I was using my own reads and the UCSC annotation. The Roberts-Pachter simulation is explained in the Online Methods of our paper (section “Simulation RNA-Seq study”). It consists of 75bp paired-end reads simulated according to parameters mimicking real data from an ENCODE embryonic stem cell line. I tested Flux Capacitor with both 10 million and 100 million simulated reads; the results are shown in the figure below:

Flux Capacitor accuracy on simulations with 10 million and 100 million reads. The top panels show scatterplots of estimated transcript abundance vs. true transcript abundance. The lower panels show the same data with both axes logged.

For comparison, the next figure shows the results of RSEM, Cufflinks and eXpress on a range of simulations (up to a billion reads) from the Roberts-Pachter paper (Figure 2a):

Modification of Figure 2a from A. Roberts and L. Pachter, Nature Methods (2013) showing the performance of Flux Capacitor in context.

Flux Capacitor has very poor performance. With 100 million reads, its performance is equivalent to other software programs at 10 million reads, and similarly, with 10 million reads, it has the performance of other programs at 1 million reads. I think its fair to say that

Using Flux Capacitor is equivalent to throwing out 90% of the data!

The simulation is a best case scenario. It adheres to the standard model for RNA-Seq in which fragments are generated uniformly at random with lengths chosen from a distribution, and with errors. As explained above, all these parameters were set according to an actual ENCODE dataset, so that the difficulty of the problem corresponds to realistic RNA-Seq data. I can’t explain the poor performance of Flux Capacitor because I don’t understand the method. However my best guess is that it is somehow solving min-flow using linear programming along the lines of the properly fomulated ideas in E. Bernard, L. Jacob, J. Mairal and J.-P. VertEfficient RNA isoform identification and quantification from RNA-seq data with network flows, Technical Report HAL-00803134, March 2013. If this is the case, the poor performance might be a result of some difficulties resulting from the minimization of isoforms and reflected in the (incorrectly estimated) stripes on the left and bottom of the log-log plots. That is not to say the conclusions of the papers where Flux Capacitor is used are wrong. As can be seen from our benchmark, although performance is degraded with Flux Capacitor, the quantifications are not all wrong. For example, abundant transcripts are less likely to be affected by Flux Capacitor’s obviously poor quantification. Still, the use of Flux Capacitor greatly reduces resolution of low-expressed genes and, as mentioned previously, is effectively equivalent to throwing out 90% of the data.

As far as GTEx is concerned, I’ve been told that a significant amount of the analysis is based on raw counts obtained from reads uniquely mapping to the genome (this approach appears to have also been used in many of the other papers where Flux Capacitor was used). Adam Roberts and I examined the performance of raw counts in the eXpress paper (Figure S8, reproduced below):

Figure S8 from A. Roberts and L. Pachter, Nature Methods (2013) showing the limits of quantification when ignoring ambiguous reads. NEUMA (Normalization by Expected Uniquely Mappable Areas) calculates an effective length for each transcript in order to normalize counts based on uniquely mappable areas of transcripts. We modified NEUMA to allow for errors, thereby increasing the accuracy of the method considerably, but its accuracy remains inferior to eXpress, which does consider ambiguous reads. Furthermore, NEUMA is unable to produce abundance estimates for targets without sufficient amounts of unique sequence. The EM algorithm is superior because it can take advantage of different combinations of shared sequence among multiple targets to produce estimates. The accuracy was calculated using only the subset of transcripts (77% of total) that NEUMA quantifies.

Quantification with raw counts is even worse than Flux Capacitor. It is not even possible to quantify 23% of transcripts  (due to insufficient uniquely mapping reads). This is why in the figure above the eXpress results are better than on the entire transcriptome (third figure of this post). The solid line shows that on the (raw count) quantifiable part of the transcriptome, quantification by raw counting is again equivalent to throwing out about 90% of the data. The dashed line is our own improvement of NEUMA (which required modifying the source code) to allow for errors in the reads. This leads to an improvement in performance, but results still don’t match eXpress (and RSEM and Cufflinks), and are worse than even Flux Capacitor if the unquantifiable transcripts are taken into account. In the recent Cufflinks 2 paper, we show that raw counts also cannot be used for differential analysis (as “wrong does not cancel out wrong”–  see my previous post on this).

One criticism of my simulation study could be that I am not impartial. After all, Cufflinks and eXpress were developed in my group, and the primary developer of RSEM, Bo Li, is now my postdoc. I agree with this criticism! This study should have been undertaken a long time ago and subjected to peer review by the author(s?) of Flux Capacitor and not by me. The fact that I have had to do it is a failure on their part, not mine. Moreover, it is outrageous that multiple journals and consortia have published work based on a method that is essentially a black box. This degrades the quality of the science and undermines scientists who do work hard to diligently validate, benchmark and publish their methods. Open source (the Flux Capacitor source code is, in fact, available for download) is not open science. Methods matter.


text:
CGAL 4.12 - Triangulated Surface Mesh Simplification
StopPredicate Concept Reference

## Definition

The concept StopPredicate describes the requirements for the predicate which indicates if the simplification process must finish.

Has Models:

CGAL::Surface_mesh_simplification::Count_stop_predicate<ECM>

CGAL::Surface_mesh_simplification::Count_ratio_stop_predicate<ECM>

CGAL::Surface_mesh_simplification::Edge_length_stop_predicate<FT>

## Types

typedef unspecified_type ECM
The type of the surface mesh to simplify. More...

typedef unspecified_type FT
A field type representing the collapse cost.

typedef unspecified_type size_type
An integer type representing the number of edges.

typedef unspecified_type Profile
The type of the edge profile cache. More...

## Operations

bool operator() (FT const &current_cost, Profile const &profile, size_type initial_count, size_type current_count) const
This predicate is called each time an edge is selected for processing, before it is collapsed. More...

## ◆ ECM

 typedef unspecified_type StopPredicate::ECM

The type of the surface mesh to simplify.

Must be a model of the EdgeCollapsableSurfaceMesh concept.

## ◆ Profile

The type of the edge profile cache.

Must be a model of the EdgeProfile concept.

## ◆ operator()()

 bool StopPredicate::operator() ( FT const & current_cost, Profile const & profile, size_type initial_count, size_type current_count ) const

This predicate is called each time an edge is selected for processing, before it is collapsed.

current_cost is the cost of the selected edge.

initial_count and current_count are the number of initial and current edges.

If the return value is true the simplification terminates before processing the edge, otherwise it continues normally.

format: plain


text:
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# 11.2: Radical Expressions

Difficulty Level: At Grade Created by: CK-12

Radicals are the roots of values. In fact, the word radical comes from the Latin word “radix,” meaning “root.” You are most comfortable with the square root symbol \begin{align*}\sqrt{x}\end{align*}; however, there are many more radical symbols.

A radical is a mathematical expression involving a root by means of a radical sign.

\begin{align*}\sqrt[3]{y}=x && \text{because} \ x^3=y && \sqrt[3]{27}=3, \ because \ 3^3=27\\ \sqrt[4]{y}=x && \text{because} \ x^4=y && \sqrt[4]{16}=2 \ because \ 2^4=16\\ \sqrt[n]{y}=x && \text{because} \ x^n=y && \end{align*}

Some roots do not have real values; in this case, they are called undefined.

Even roots of negative numbers are undefined.

\begin{align*}\sqrt[n]{x}\end{align*} is undefined when \begin{align*}n\end{align*} is an even whole number and \begin{align*}x<0\end{align*}.

Example 1: Evaluate the following radicals:

• \begin{align*}\sqrt[3]{64}\end{align*}
• \begin{align*}\sqrt[4]{-81}\end{align*}

Solution: \begin{align*}\sqrt[3]{64} = 4\end{align*} because \begin{align*}4^3=64\end{align*}

\begin{align*}\sqrt[4]{-81}\end{align*} is undefined because \begin{align*}n\end{align*} is an even whole number and \begin{align*}-81<0\end{align*}.

In Chapter 8, you learned how to evaluate rational exponents:

\begin{align*}a^{\frac{x}{y}} \ where \ x=power \ and \ y=root\end{align*}

This can be written in radical notation using the following property.

Rational Exponent Property: For integer values of \begin{align*}x\end{align*} and whole values of \begin{align*}y\end{align*}:

\begin{align*}a^{\frac{x}{y}}= \sqrt[y]{a^x}\end{align*}

Example: Rewrite \begin{align*}x^{\frac{5}{6}}\end{align*} using radical notation.

Solution: This is correctly read as the sixth root of \begin{align*}x\end{align*} to the fifth power. Writing in radical notation, \begin{align*}x^{\frac{5}{6}}=\sqrt[6]{x^5}\end{align*}, where \begin{align*}x^5>0\end{align*}.

Example 2: Evaluate \begin{align*}\sqrt[4]{4^2}\end{align*}.

Solution: This is read, “The fourth root of four to the second power.”

\begin{align*}4^2=16\end{align*}

The fourth root of 16 is 2; therefore,

\begin{align*}\sqrt[4]{4^2}=2\end{align*}

In Chapter 1, Lesson 5, you learned how to simplify a square root. You can also simplify other radicals, like cube roots and fourth roots.

Example: Simplify \begin{align*}\sqrt[3]{135}\end{align*}.

Solution: Begin by finding the prime factorization of 135. This is easily done by using a factor tree.

\begin{align*}&\sqrt[3]{135}= \sqrt[3]{3 \cdot 3 \cdot 3 \cdot 5} = \sqrt[3]{3^3} \cdot \sqrt[3]{5}\\ & 3 \sqrt[3]{5}\end{align*}

To add or subtract radicals, they must have the same root and radicand.

\begin{align*}a \sqrt[n]{x}+b\sqrt[n]{x}=(a+b)\sqrt[n]{x}\end{align*}

Example 3: Add \begin{align*}3\sqrt{5}+6\sqrt{5}\end{align*}.

Solution: The value “\begin{align*}\sqrt{5}\end{align*}” is considered a like term. Using the rule above,

\begin{align*}3 \sqrt{5}+6\sqrt{5}=(3+6) \sqrt{5}=9\sqrt{5}\end{align*}

Example: Simplify \begin{align*}2\sqrt[3]{13} + 6 \sqrt[3]{12}\end{align*}.

Solution: The cube roots are not like terms, therefore there can be no further simplification.

In some cases, the radical may need to be reduced before addition/subtraction is possible.

Example 4: Simplify \begin{align*}4\sqrt{3}+2\sqrt{12}\end{align*}.

Solution: \begin{align*}\sqrt{12}\end{align*} simplifies as \begin{align*}2\sqrt{3}\end{align*}.

\begin{align*}4\sqrt{3}+2\sqrt{12} &\rightarrow 4\sqrt{3}+2\left ( 2\sqrt{3} \right )\\ 4\sqrt{3}+4\sqrt{3}&=8\sqrt{3}\end{align*}

## Multiplying or Dividing Radicals

To multiply radicands, the roots must be the same.

\begin{align*}\sqrt[n]{a} \cdot \sqrt[n]{b}= \sqrt[n]{ab}\end{align*}

Example: Simplify \begin{align*}\sqrt{3} \cdot \sqrt{12}\end{align*}.

Solution: \begin{align*}\sqrt{3} \cdot \sqrt{12}=\sqrt{36}=6\end{align*}

Dividing radicals is more complicated. A radical in the denominator of a fraction is not considered simplified by mathematicians. In order to simplify the fraction, you must rationalize the denominator.

To rationalize the denominator means to remove any radical signs from the denominator of the fraction using multiplication.

Remember: \begin{align*}\sqrt{a} \times \sqrt{a}= \sqrt{a^2}=a\end{align*}

Example 1: Simplify \begin{align*}\frac{2}{\sqrt{3}}\end{align*}.

Solution: We must clear the denominator of its radical using the property above. Remember, what you do to one piece of a fraction, you must do to all pieces of the fraction.

\begin{align*}\frac{2}{\sqrt{3}} \times \frac{\sqrt{3}}{\sqrt{3}}=\frac{2\sqrt{3}}{\sqrt{3^2}}=\frac{2\sqrt{3}}{3}\end{align*}

Example: Simplify \begin{align*}\frac{7}{\sqrt[3]{5}}\end{align*}.

Solution: In this case, we need to make the number inside the cube root a perfect cube. We need to multiply the numerator and the denominator by \begin{align*}\sqrt[3]{5^2}\end{align*}.

\begin{align*}\frac{7}{\sqrt[3]{5}} \cdot \frac{\sqrt[3]{5^2}}{\sqrt[3]{5^2}}=\frac{7^3\sqrt{25}}{\sqrt[3]{5^3}}=\frac{7^3\sqrt{25}}{5}\end{align*}

Example: A pool is twice as long as it is wide and is surrounded by a walkway of uniform width of 1 foot. The combined area of the pool and the walkway is 400 square-feet. Find the dimensions of the pool and the area of the pool.

Solution:

1. Make a sketch.
2. Let \begin{align*}x=\end{align*} the width of the pool.
3. Write an equation. \begin{align*}Area=length \cdot width\end{align*}

Combined length of pool and walkway \begin{align*}=2x+2\end{align*}

Combined width of pool and walkway \begin{align*}=x+2\end{align*}

\begin{align*}\text{Area}=(2x+2)(x+2)\end{align*}

Since the combined area of pool and walkway is \begin{align*}400 \ ft^2\end{align*} we can write the equation.

\begin{align*}(2x+2)(x+2)=400\end{align*}

4. Solve the equation:

\begin{align*}&& & (2x+2)(x+2)=400\\ & \text{Multiply in order to eliminate the parentheses}. && 2x^2+4x+2x+4=400\\ & \text{Collect like terms}. && 2x^2+6x+4=400\\ & \text{Move all terms to one side of the equation}. && 2x^2+6x-396=0\\ & \text{Divide all terms by} \ 2. && x^2+3x-198=0\end{align*}

\begin{align*}x & = \frac{-b\pm \sqrt{b^2-4ac}}{2a}\\ & = \frac{-3 \pm \sqrt{3^2-4(1)(-198)}}{2(1)}\\ & = \frac{-3\pm \sqrt{801}}{2} \approx \frac{-3\pm 28.3}{2}\end{align*}

Use the Quadratic Formula. \begin{align*}x \approx 12.65\end{align*} or –15.65 feet

5. We can disregard the negative solution since it does not make sense for this context. Thus, we can check our answer of 12.65 by substituting the result in the area formula.

\begin{align*}\text{Area} = [2(12.65)+2)](12.65+2)=27.3 \cdot 14.65 \approx 400 \ ft^2.\end{align*}

The answer checks out.

## Practice Set

Sample explanations for some of the practice exercises below are available by viewing the following videos. Note that there is not always a match between the number of the practice exercise in the videos and the number of the practice exercise listed in the following exercise set.  However, the practice exercise is the same in both.

1. For which values of \begin{align*}n\end{align*} is \begin{align*}\sqrt[n]{-16}\end{align*} undefined?

Evaluate each radical expression.

1. \begin{align*}\sqrt{169}\end{align*}
2. \begin{align*}\sqrt[4]{81}\end{align*}
3. \begin{align*}\sqrt[3]{-125}\end{align*}
4. \begin{align*}\sqrt[5]{1024}\end{align*}

Write each expression as a rational exponent.

1. \begin{align*}\sqrt[3]{14}\end{align*}
2. \begin{align*}\sqrt[4]{zw}\end{align*}
3. \begin{align*}\sqrt{a}\end{align*}
4. \begin{align*}\sqrt[9]{y^3}\end{align*}

Write the following expressions in simplest radical form.

1. \begin{align*}\sqrt{24}\end{align*}
2. \begin{align*}\sqrt{300}\end{align*}
3. \begin{align*}\sqrt[5]{96}\end{align*}
4. \begin{align*}\sqrt{\frac{240}{567}}\end{align*}
5. \begin{align*}\sqrt[3]{500}\end{align*}
6. \begin{align*}\sqrt[6]{64x^8}\end{align*}
7. \begin{align*}\sqrt[3]{48a^3b^7}\end{align*}
8. \begin{align*}\sqrt[3]{\frac{16x^5}{135y^4}}\end{align*}
9. True or false? \begin{align*}\sqrt[7]{5} \cdot \sqrt[6]{6}=\sqrt[42]{30}\end{align*}

Simplify the following expressions as much as possible.

1. \begin{align*}3\sqrt{8}-6\sqrt{32}\end{align*}
2. \begin{align*}\sqrt{180}+6\sqrt{405}\end{align*}
3. \begin{align*}\sqrt{6}-\sqrt{27}+2\sqrt{54}+3\sqrt{48}\end{align*}
4. \begin{align*}\sqrt{8x^3}-4x\sqrt{98x}\end{align*}
5. \begin{align*}\sqrt{48a}+\sqrt{27a}\end{align*}
6. \begin{align*}\sqrt[3]{4x^3}+x\sqrt[3]{256}\end{align*}

Multiply the following expressions.

1. \begin{align*}\sqrt{6}\left ( \sqrt{10} + \sqrt{8} \right )\end{align*}
2. \begin{align*}\left ( \sqrt{a} - \sqrt{b} \right ) \left ( \sqrt{a} + \sqrt{b} \right )\end{align*}
3. \begin{align*}\left ( 2\sqrt{x}+ 5 \right ) \left ( 2\sqrt{x}+5 \right )\end{align*}

Rationalize the denominator.

1. \begin{align*}\frac{7}{\sqrt{15}}\end{align*}
2. \begin{align*}\frac{9}{\sqrt{10}}\end{align*}
3. \begin{align*}\frac{2x}{\sqrt{5}x}\end{align*}
4. \begin{align*}\frac{\sqrt{5}}{\sqrt{3}y}\end{align*}
5. The volume of a spherical balloon is \begin{align*}950 cm^3\end{align*}. Find the radius of the balloon. (Volume of a sphere \begin{align*}=\frac{4}{3} \pi R^3\end{align*})
6. A rectangular picture is 9 inches wide and 12 inches long. The picture has a frame of uniform width. If the combined area of picture and frame is \begin{align*}180 in^2\end{align*}, what is the width of the frame?
7. The volume of a soda can is \begin{align*}355 \ cm^3\end{align*}. The height of the can is four times the radius of the base. Find the radius of the base of the cylinder.

Mixed Review

1. An item originally priced \begin{align*}\c\end{align*} is marked down 15%. The new price is 612.99. What is \begin{align*}c\end{align*}? 2. Solve \begin{align*}\frac{x+3}{6}=\frac{21}{x}\end{align*}. 3. According to the Economic Policy Institute (EPI), minimum wage in 1989 was3.35 per hour. In 2009, it was 7.25 per hour. What is the average rate of change? 4. What is the vertex of \begin{align*}y=2(x+1)^2+4\end{align*}? Is this a minimum or a maximum? 5. Using the minimum wage data (adjusted for inflation) compiled from EPI, answer the following questions. 1. Graph the data as a scatter plot. 2. Which is the best model for this data: linear, quadratic, or exponential? 3. Find the model of best fit and use it to predict minimum wage adjusted for inflation for 1999. 4. According to EPI, the 1999 minimum wage adjusted for inflation was6.58. How close was your model?
5. Use interpolation to find minimum wage in 1962.
Year Minimum Wage Adj. for Inflation Year Minimum Wage Adj. for Inflation
1947 3.40 1952 5.36
1957 6.74 1960 6.40
1965 7.52 1970 7.81
1978 7.93 1981 7.52
1986 6.21 1990 6.00
1993 6.16 1997 6.81
2000 6.37 2004 5.80
2006 5.44 2008 6.48
2009 7.25

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text: Paiye sabhi sawalon ka Video solution sirf photo khinch kar. - Get the answer to this question and access a vast question bank that is tailored for students. … Add your answer and earn points. Among the following elements, which one exhibits both positive and negative oxidation states? To find this oxidation number, it is important to know that the sum of the oxidation numbers of atoms in compounds that are neutral must equal zero. What is the oxidation number of sulfur in Na2S2O4. ... Cl is -1 so S has to be +2 SO2 - +4, O is -2 SO3 - +6, the same reason H2SO4 - +6, O is -2, H is +1. Sulphur bonded to three oxygen is considered to have +6 (Sulphur A) and other sulphur has -2 (Sulphur B). Chemistry, 30.06.2020 15:01, sierras0330 Oxidation number of sulphur in H2SO4 Classification of Elements and Periodicity in Properties, The oxidation number of sulphur in H2SO4, H2S2O4 and H2S2O6 are respectively. The sum of the oxidation numbers is zero for a compound, and the charge on the ion for an ion. Answered Oxidation number of sulphur in H2SO4 See answer The oxidation number of O in compounds is usually -2, but it is -1 in peroxides. Thus, [oxidation state of S x 4] + [(-2) (6)] = -2 Let color (red) y be the oxidation state of S. please follow me and mark as brainliest Calculate the oxidation number of sulphur in AL2(SO4)3 ... + H2SO4(aq) → Al2(SO4)3(aq) + H2(g) What is the coefficient of H2 in the balanced equation, obtained by using oxidation numbers? Chemistry. Lv 7. chemistry. The oxidation number is synonymous with the oxidation state. S = 4 The oxid'n number of sulphur. Therefore, the oxidation number of sulfur in the compound is -2, and the sum of the oxidation numbers is 0. SO2(g) + H2O(l) → H2SO3(l) What mass of sulfur dioxide is . Click here to get an answer to your question  what is the oxidation number of sulphur in H2so4 abu338452 abu338452 35 minutes ago Chemistry Secondary School What is the oxidation number of sulphur in H2so4 2 See answers abu338452 is waiting for your help. 1 answer. Ans-B In H2SO4, the oxidation number of H is +1, that of S is +6,& that of O is -2. Ans-A In CaF2, the oxidation number of Ca is +2,& that of F is -1. I recommend reading it thoroughly. Sulfur dioxide will react with water to form sulfurous acid (see balanced equation below). Log in. asked Oct 9, 2017 in Chemistry by jisu zahaan (29.7k points) redox reaction; cbse; 0 votes. The oxidation number (O.N.) Also hydrogen has different oxidation numbers, -1, 0, +1 . $\endgroup$ – Eashaan Godbole May 20 '19 at 14:34 $\begingroup$ Note that an oxidation number of $+8$ on $\ce{S}$ would require to open up the 2p shell, which does not happen for sulfur. it is +6. CRYSTALLIZATION OF A PROTEIN WITH A SULPHUR SALT. How many moles of sulfur are present in 2.9 moles of Al2(SO4)3 . Relevance. MgSO4 +H2O Use oxidation numbers to identify which element has been oxidised and explain. The oxidation number of sulphur in sulphuric acid H2SO4 is Ask for details ; Follow Report by SYLTANMIRZA 21.09.2019 Log in to add a comment The oxidation number of sulphur in S_(8),S_(2)F_(2),H_(2)S and H_(2)SO_(4) respectively are: Doubtnut is better on App. Oxygen is almost always -2. But H2SO4 is a neutral compound to neutralize this compound sulfer show the overall valence of +6.Hence it shows +6 charge to stable the compound. Oxidation number of hydrogen in H 2 is +1. the equivalent weight of ferrous ion. We can find these numbers on the periodic table. H2SO4 Oxidation number of H = +1 Oxidation number of O = -2 Let oxidation number of sulfur be X. Bonds between atoms of the same element (homonuclear bonds) are always divided equally. NCERT P Bahadur IIT-JEE Previous Year Narendra Awasthi MS Chauhan. Get an answer to your question “The oxidation number of S in H2SO4 is: * ...” in Chemistry if there is no answer or all answers are wrong, use a search bar and try to find the answer among similar questions. pulakmath007 pulakmath007 Answer: Oxidation Number of Oxygen= -2. Sulphur bonded to three oxygen is considered to have +6 (Sulphur A) and other sulphur has -2 (Sulphur B). Log in. So overall oxidation number of sulphur is - 8+2=-6 . 4. You set it up like an algebraic equation and solve for S, the unknown oxidation … Oxidation Number It is an artificial concept to help with redox reactions. 6. i.e., the oxidation number of 2 oxygen atoms is -2. Indeed, +6− 1 2 = 2.5. -6 +2 +4 +6 - e-eduanswers.com of C. The two carbon atoms present in this molecule are present in different environments. Flats on Carpenter. 2 0. pisgahchemist. The sum of the oxidation numbers in a compound must equal zero. +2.5 (No, this isn't an anomaly. Calculate Physics. What is the oxidation Number of sulfur in SO2 and SO3? What is the oxidation number of sulphur in H2so4 2 See answers abu338452 is waiting for your help. Chemistry . Answer and Explanation: The compound H2SO4 H 2 S O 4 is a neutral compound. CRYSTALLIZATION OF A PROTEIN WITH A SULPHUR SALT. Then , 2 x (+1) + X + 4 x (-2) = 0 Solving we get, +2 + X - 8 = 0 X = +6 Thus oxidation number of sulfur in H2SO4 is +6. Sulphur atom in the sulphur dioxide molecule is reduced to sulfur while sulphur atom in the hydrogen sulphide is oxidized to sulfur. What is the oxidation number of oxygen in CO2-2. If you have learned the electronegativity rules yet, here is a good place to use. Calculate the oxidation number of sulphur in $\ce{H2SO5}$? In Naâ Sâ Oâ , the oxidation number of S is +5. Answer to: Determine the oxidation number of each element in H2SO4. Use a … FLATS ON CARPENTER; About; Properties; Parking; Residents. What is the overall change in the oxidation number of sulfur for this . Completing the CAPTCHA proves you are a human and gives you temporary access to the web property. 12 months ago. How tried it: \begin{align} 2(+1) + 1(x) + 5(-2) &= 0\\ 2 + x - 10 &= 0\\ x&=\pm8 \end{align} oxidation-state. So that sulfur atom can be oxidized to sulfur's other higher oxidation states such as 0, +2 and +6. Substituting HSO_4^- with its oxidation state values we have: (+1) + x + [(-2) * (4)] = - What is the oxidation number of sulfur in SO2. Books. 1 Answer The oxidation number of a free element is always 0. Let x be the oxidation number of sulphur in sulphuric acid. nitrogen(II) oxide. Determining oxidation numbers from the Lewis structure (Figure 1a) is even easier than deducing it from the molecular formula (Figure 1b). What is the oxidation number of vanadium in $R{{b}_{4}}Na[H{{V}_{10}}{{O}_{28}}]$ ? Relevance. $\ce{H2SO5}$ exists it is named as "peroxy sulfuric acid". oxidation number of H = +1. (a) +2 +2x -6=0 x= +2 b) +2 +4x -12=0 x= +2.5 c) +2 +x -6=0 x= +4 d) +2 +x -8=0 x= +6. I. E x = +6. 1 decade ago. Substituting HSO_4^- with its oxidation state values we have: (+1) + x + [(-2) * (4)] = - 2- Besides the French Revolution the effect on Romantic Revolution: a- American Revolution b- Napoleonic wars So SO2 has S+4 and SO3 has S+3. What is the oxidation number of sulfur in Na2S2O4. We can find oxidation numbers of sulfur and hydrogen in H 2 S by several methods.. It has very little physical meaning. Solution for What is the oxidation number of sulfur (S) in sulfuric acid (H2SO4)? Potassium has a +1 charge. Name the compound SO2 using the Stock system. sulfur(IV) oxide. Identify compound X in the following sequence of reactions: Identify a molecule which does not exist. What volume of 0.490 M H2SO4 is needed to react with excess aluminum to produce 1.60 g of Al2(SO4)3? MgSO4 +H2O Use oxidation numbers to identify which element has been oxidised and explain. NCERT DC Pandey Sunil Batra HC Verma Pradeep Errorless. In H2SO4, the hydrogen atoms create 2*(+1) charge and the oxygen atoms create 4*(-2) charge. But H2SO4 is a neutral compound to neutralize this compound sulfer show the overall valence of +6.Hence it shows +6 charge to stable the compound. They are not the actual charges on atoms in compounds. The oxidation number of sulphur in $S_{8}$ molecule is. What is to bolster as Battery is to torch? What is the oxidation number of sulfur in H2SO4. (Compare hydrogen peroxide, H 2 O 2) 2 atoms of oxygen will get -1 oxidation number each. Over the range of conditions studied, the rate of sulfur dioxide oxidation is zero-order in oxygen, ï¬ rst-order in sulfur dioxide and inhibited by sulfur trioxide. In H2SO5, one peroxide bond is present. In Peroxydisulphiric acid (H2S2O8) has sulphur in the +6 oxidation state, hydrogen in the +1 oxidation state, the two O's between the two S-atoms are in the -1 oxidation state and all other oxygens are in the -2 oxidation state. You may need to download version 2.0 now from the Chrome Web Store. Oxygen almost always has an oxidation number of −2, so 4 oxygen atoms means the charge is 8 −. H2SO4 is a compound and as such does not have an oxidation number. Find an answer to your question Calculate the oxidation number of sulphur in H2SO4 danichenwo danichenwo 10/09/2020 Chemistry High School Calculate the oxidation number of sulphur in H2SO4 1 See answer danichenwo is waiting for your help. Give the oxidation number of sulfur in the following:(a) SOCl2 (b) H2S2 (c) H2SO3 (d) Na2S Solution 51PHere, we have to calculate the oxidation number of sulfur in each of the following.Step 1 of 4a.SOCl2Oxidation state of oxygen = -2Oxidation state of Chlorine = -1.S + 1(-2) + 2(-1) = 0S - 2 -2 =0S - … Cloudflare Ray ID: 60e1f2b0a980e25f SciMann. Oxidation numbers are assigned numbers. Uncategorized The oxidation number of H is +1, but it is -1 in when combined with less electronegative elements. Relevance. SO4 has -2 oxd. 6 Answers. H2SO4 is a compound and as such does not have an oxidation number. In the compound sulfur dioxide (SO2), the oxidation number of oxygen is -2. Oxidation number ... S . Reaction between acetone and methyl magnesium chloride followed by hydrolysis will give : Identify the correct statements from the following: Which of the following set of molecules will have zero dipole moment ? Favorite Answer. Which of them does not react with aqueous solution of $KMnO_4$ in presence of $H_2SO_4$ ? On electrolysis of dil.sulphuric acid using Platinum (Pt) electrode, the product obtained at anode will be: An element has a body centered cubic (bcc) structure with a cell edge of 288 pm. First we need to calculate the oxidation state of S atom the usual way. of sulphur â ¦ In thiosulphate, two sulphurs have oxidation state of -2 and +6. The oxidation no. According to the structure, the symmetry suggests a −1 on each bridging sulfur (blue) (just like the bridging O atoms in a peroxide), and a +6 (red) on each central sulfur (like in sulfate). Sulfur, in this case, has an oxidation number of +6, which means that SO4 ion has an overall charge … The oxidation number for sulfur in SO2 is +4. The remaining 3 atoms will have +2 oxidation number each. Ans-C In CaSO4, the oxidation number of Ca is +2, that of S is +6,& that of O is -2. As a whole it has oxidation number 0. 0 votes . The oxidation number of sulphur in sulphuric acid h2so4 is? Oxidation Number: By default, the oxidation number of hydrogen and oxygen are +1 and -2, respectively, in most circumstances but there are exceptions. 1 7. so Sulfur must be a +6 each, for the molecule H2SO4 … All the bonds are covalent. Oxidation state of sulphur in oleum is +6. Steve O. Lv 7. Sulphur bonded to three oxygen is considered to have +6 (Sulphur A) and other sulphur has -2 (Sulphur B). Answer Save. Draw the structure of (i) H2S2O8 (ii) H2S2O7. Add your answer and earn points. Solution for (1) Calculate oxidation number of: a) Cr in CrO7 2- (b) P in Na2HPO4 (c) S in H2SO4 (11) Write the balanced equation for the reaction when: zinc… Hence, the fractional oxidation state. Ask your question. Sulfur can have many oxidation states in this method. Ans-D In HF, the oxidation number of H is +1,& that of F is -1. Find an answer to your question Oxidation number of sulphur in H2SO4 1. Different ways of displaying oxidation numbers of ethanol and acetic acid. In thiosulphate, two sulphurs have oxidation state of -2 and +6. let x= oxidation number of sulphur, and +1 is oxidation number of Na, -2 is oxidation number of O, also assume total charge on compound = 0 then solving we get. That means the algebraic sum of all the anion or cation numbers is zero. Check A Chemistry. So, in SO3, in order to create a net neutral, or zero charge, the S must have an oxidation number 6+ to cancel out the 3*(-2)= -6 of the oxygen in the compound. Choose the disproportionation reaction among the following redox reactions. Calculate the oxidation number of sulphur in AL2(SO4)3 . Figure 1. The sum of the oxidation states equals zero. Certain elements have commonly assigned oxidation numbers: Hydrogen is +1. 1 decade ago. Explanation: 2(+1) + x + 4 (-2) = 0. x-6 = 0. What is to bolster as Battery is to torch? Lv 7. In the reaction, $3B{{r}_{2}}+6CO_{3}^{2-}+3{{H}_{2}}O\xrightarrow{{}}5B{{r}^{-}}$ $+BrO_{3}^{-}+6\,HCO_{3}^{-}$ Choose the correct statement. Another way to prevent getting this page in the future is to use Privacy Pass. Find differences of oxidation numbers. If you are at an office or shared network, you can ask the network administrator to run a scan across the network looking for misconfigured or infected devices. Oxygen is -2. 2- Besides the French Revolution the effect on Romantic Revolution: a- American Revolution b- Napoleonic wars Hence, they cannot have the same oxidation number. Thus, C exhibits the oxidation states of +2 and –2 in CH 3 COOH. However, 0 is average O.N. H2SO4 has no overall charge, so the sum of the oxidation numbers must be equal to 0. Correct answer to the question What is the oxidation number of sulfur (s) in sulfuric acid (h2so4)? Favourite answer. Sufuric acid is a molecule: it is not an element. feyisayoadebajo feyisayoadebajo 06/30/2020 Chemistry High School +5 pts. Oxygen has an oxidation number of 2-. Biology. Your teacher used an interesting example that doesn't obey the rules cleanly. Ask your question. The atomic radiusis: Find out the solubility of $Ni(OH)_2$ in 0.1 M NaOH. In sulfuric acid, the molecular formula is H2SO4. of sulphur â ¦ In thiosulphate, two sulphurs have oxidation state of -2 and +6. The oxidation number of each atom can be calculated by subtracting the sum of lone pairs and electrons it gains from bonds from the number of valence electrons. Answer Save. what is the oxidation number of sulfur in H2SO4? The individual atoms in this compound have oxidation number +1 for each hydrogen atom, +6 for sulfur, and -2 for each oxygen Relevance. The individual atoms in this compound have oxidation number +1 for each hydrogen atom, +6 for sulfur, and -2 for each oxygen atom. • With six covalent bonds with four different oxygen atoms, sulfur has +6 oxidation number. There should be rules for determining oxidation states in your book. Hope it helped! Oxidation number of sulfur in H 2 is -2. Answer to: Determine the oxidation number of each element in H2SO4. Performance & security by Cloudflare, Please complete the security check to access. Al(s) + H2SO4(aq)-> Al2(SO4)3(aq) + H2(g) Consider the unbalanced equation above. • The oxidation number of sulfur in sulfate anion (SO42-) and in sulfuric acid (H2SO4), respectively, are? Use MathJax to format equations. -6 +2 +4 +6 If you are on a personal connection, like at home, you can run an anti-virus scan on your device to make sure it is not infected with malware. In Wolff‐Kishner reduction, the carbonyl group of aldehydes and ketones is converted into. So overall oxidation number of sulphur is - 8+2=-6 . What is Oxidation Number of sulphur in H2SO4? Oxidation number, also called Oxidation State, the total number of electrons that an atom either gains or loses in order to form a chemical bond with another atom. Question: Calculate Oxidation Number Of: (a) Cr In Cr2O7 2- (b) P In Na2HPO4 (c) S In H2SO4 (ii) Write The Balanced Equation For The Reaction When Zinc Sulphide Reacts With Oxygen Giving Zinc Oxide And Sulphur … We also know that since there is no charge on the compound, all the oxidation numbers add up to 0. Sulfur trioxide, SO3, is made from the oxidation of SO2, and the reaction is represented by the equation 2SO2 + O2 2SO3 A 25-g sample of SO2 gives 18 g of SO3. (as per suggestions). chemistry. Join now. What is the oxidation number of gold in the complex $\ce{[AuCl_4]^{1-}}$ ? S_4O_6^"2-" : overall oxidation state is -2 [oxidation state of S x 4] + [oxidation state of O atom x 6] = -2 The most common oxidation state of oxygen is -2. 4 oxygen at -2 each adds up to -8, 2 hydrogens @ +1 each, add up to +2. Chemistry. of H is +1. $\begingroup$ Structures are more important than chemical formulae while finding oxidation numbers of individual atoms. In the compound hydrogen sulfide, H2S, the two hydrogen atoms have an oxidation number of +1, for a total of +2. Hydrogen has an oxidation number of 1+. (The answer is given as as $+6$.) Квартиры, виллы, участки, коттеджи и дома на Северном Кипре. share | improve this question | follow | edited May 20 '19 at 12:57. 1.6K views View 1 Upvoter H2SO4 is a compound and as such does not have an oxidation number. Elemental sulfur can be converted to sulfur dioxide by combustion in air. An example of a disproportionation reaction is : Consider the following reduction processes : 1 mole of $FeSO_4$ (atomic weight of Fe is $55.84 \, g \, mol^{-1}$) is oxidized to $Fe_2(SO_4)_3$. But, sulfur atom cannot be reduced furthermore because -2 is the lowest oxidation state of sulfur. Let me explain first.) Квартиры, виллы, участки, коттеджи и дома на Северном Кипре. What Is The Oxidation State Of The Sulfur Atom In SO2? of sulphur in H2SO3 , H2SO4 , H2SO5 or sulphuric acid, Caro’s acid (permono sulphuric acid) is respectively___ asked Apr 4, 2019 in Redox reactions and electrochemistry by Simrank ( … x + 3(+1) + x + (-2) + (-2) + 1(+1) = 0 ⇒ 2x + 3 - 2 - 2 + 1 = 0 ⇒ 2x + 0 = 0 ⇒ x = 0. Luxury Uptown Apartments. Oxidation number, also called Oxidation State, the total number of electrons that an atom either gains or loses in order to form a chemical bond with another atom. of -2, and that alkali metals and alkali earth metals have oxidation numbers corresponding to their charges. The oxidation number of sulphur in H2SO4, H2S2O4 and H2S2O6 are respectively (A) +3, +4, +5 (B) +5, +4, +3 (C) +6, +3, + 5 (D) +3, +5, +4. Name the compound N2O2 using the Stock system. H 2 S Oxidation Number | Oxidation State of Sulfur in H 2 S. Sulfur forms different oxidation numbers from -2 to +6. The oxidation number of each atom can be calculated by subtracting the sum of lone pairs and electrons it gains from bonds from the number of valence electrons. 2(+1) + 1(+6) + 4(-2) = 0 ===== Follow up ===== Joshua is a bit confused as well. Sulphur cannot have more than +6 oxidation number as it belongs to VI(A) group. The oxidation number rules state that most every time, oxygen will have an O.N. oxidation number of O = -2. let late oxidation number of Sulphur be 'x' H2SO4 +1*2 + X + (-2)*4. by solving we get, I hope this helps you. The oxidation number of sulphur in H2SO4 is: (i) – 2 (ii) +2 (iii) + 5 (iv) + 4 (v) None of these Educators Sample Paper-1 (MCQs Solved) 1- Lyrical Ballads opens with; a- Tintern Abbey b- Michael c- Dejection: an Ode d- Rime of Ancient Mariner e- Immortality Ode. Then we got: Oxidation number of Oxygen= -2 Oxidation number of Hydrogen= +1 1 ⋅ 2 + x − 2 ⋅ 4 = 0 2 + x − 8 = 0. x − 6 = 0. x = 6 I recommend reading it thoroughly. The oxidation number of a monatomic ion equals the charge of the ion. 1.6K views View 1 Upvoter H2SO4 is a compound and as such does not have an oxidation number. $\endgroup$ – TAR86 May 20 '19 at 16:24 2 Answers. 1. remmeigaiguilunglu remmeigaiguilunglu Answer: +6. Join now. Please enable Cookies and reload the page. Given that the ionic product of $Ni(OH)_2$ is $2 \times 10^{-15}$. Open App Continue with Mobile Browser. The oxidation number of sulphur in H2SO4 is: (i) – 2 (ii) +2 (iii) + 5 (iv) + 4 (v) None of these Educators Sample Paper-1 (MCQs Solved) 1- Lyrical Ballads opens with; a- Tintern Abbey b- Michael c- Dejection: an Ode d- Rime of Ancient Mariner e- Immortality Ode. Your IP: 128.199.143.245 May 20 '19 at 16:24 so overall oxidation number of sulfur and in! To bolster as Battery is to Use converted to sulfur dioxide by combustion in air of... The molecule H2SO4 … There should be rules for determining oxidation states such as 0, +2 and.. For your help +2.5 ( no, this is n't an anomaly +1,. 8 } $exists it is -1 every time, oxygen will Get -1 number! Access to the question what is the oxidation number of sulfur ( S ) in sulfuric (... H2So4 H 2 O 2 ) 2 atoms of oxygen is considered to have +6 sulphur. Sulphur in sulphuric acid 0.490 M H2SO4 is and Explanation: 2 ( +1 ) + H2O ( )! 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Simple (postscript) printer setup in OpenBSD 4.3

Printing in UNIX may sometimes be somewhat of a hurdle. This is also very dependent on which type of setup you want (local or remote and which software to use) and which type of printer you have.

In general you need; a properly configured printer driver towards the printer (assumes a local printer) and a spooler which handles queue management of print jobs. In addition you may use print filters which are able to convert input to a suitable format understandable by the printer.

Printer setup is not much different in OpenBSD compared to any other UNIX system (e.g. FreeBSD). Most programs needed are available in packages collection. I would highly recommend Dru Lavigne UNIX Pringting Overview for a good start for UNIX printing.

I explain the simple setup I needed to do for my USB connected printer, HP LaserJet 1320.

First you need to identify a suitable driver for you printer. I checked linuxprinting.org for my printer and the printer manual. Here I found out that my printer has (emulates) postscript but for full capabilites I need HPLIP driver. The hplip-2.7.10 driver is available in the packages. But as this requires quite a lot of extra effort (see install message) I just stick the emulated postscript support which is the easiest setup.

My printer is connected to USB which is automatically identified at boot. A virtual printer device is setup on /dev/ulpt0 which can be seen in dmesg output.

# dmesg
...
ulpt0 at uhub1 port 2 configuration 1 interface 0 "Hewlett-Packard hp LaserJet 1320 series" rev 1.10/1.00 addr 3
ulpt0: using bi-directional mode
...

You may want to try to send something directly to the printer device. lptest just print a character stream.

# lptest 70 5 > /dev/ulpt0

Something should show up on the printer. I only does this after printing a test page (directly on the printer) afterwards.

Next step is to setup the spooler. This is done using apsfilter which is the simplest setup. Install apsfilter from packages and run the setup utility (logged in as root).

# pkg_add apsfilter-7.2.8p0
# /etc/apsfilter/basedir/SETUP

Just follow the instructions during the configuration. Because my printer support postscript this setup is really simple. In the main menu you are also able to print a test page which is very useful to see that everything is working. See Printing for the Impatient for more information about this.

After this you should have a working configuration stored in /etc/printcap. The last step is to start the spooler deamon lpd. Start it from command line by issuing lpd and add it to /etc/rc.conf.local to start it at boot time.

lpd_flags=""		# for normal use: ""

Now everything should be setup with printing support. Try printing a page from e.g. firefox.