hello students today we are going to start 1 chapter of class 11 chemistry
so we will study the first chapter of chemistry which is basic concepts of chemistry
 
 
In this, we see  why chemistry is important and which chemical we use and what are the significant
how it helps us in many ways what is a significant figure  what is an element
what is mixture all these basic we will not do
which is some basic parts of chemistery
we will tell you what is a chemical combination and we will tell you that what is the law of combination
 
so the laws of chemical combination we will study today
there are 5 big laws in chemistry yes there are 5 big laws
 
who decide how the element will combine
and  form compound {repeated}
 
 
 
so a mass of one element form compound form with other elements
in which percentage it will react in how many moles
which gas will divide in which ratio
all these things
are decide  by 5 laws says laws of chemical
combination
so we will start laws of combination
and the first and first law is studied by all
law of conservation of mass
law of conservation of mass
so I tell these all things were discovered in the 1740s and 1780s
it means all these concepts are too old  so no new laws will be added
so the law of conservation says that
 
in chemistry when two compounds are combined they form a new compound
so the  mass  of two compounds on one side is equal to newly formed compound
 
that means mass can be  neither be created nor be destroyed
the  mass  of two compounds on one side is equal to newly formed compound
 
means the sum of the mass of reactants should be equal to the sum of the mass of products
 
it  is too basic still I want that you will make notes of these concepts
put a heading law of chemical combination and start note making
so 1 law is sum of the mass of reactants should be equal to the sum of the mass of products
 
so we start this story with examples
carbon  combined with oxygen to give carbon dioxide
this reaction is balanced  1 carbon  and 2 oxygen
 
the atomic mass of carbon is 12 and mass oxygen is 16
see how many carbons are there is 12
and oxygen is 16 multiply 2 is 32
and how carbon dioxide will form
12+16 multiply by 2
it becomes 44
 
do sum of these 2 it becomes 44 and another side also it is 44
the sum of the mass of reactant is equal to the sum of the mass of product
so it is not a big thing it is too simple
everybody knows that
when a chemical reaction occurs the sum of the mass of reactant is equal to the sum of the mass of product applied
nowadays it is not applicable because
you all know that there are some reactions in which
E=MC^2 IS applied
and some mass released  in the forms of energy
but these are very old laws
and in that time these things were no discussed
so buddy question arises
we come with a question let see
you are able to do or not first question is good
and the question is
1.5 gram of ethane
1.5 gram of ethane
on complete combustion
gives
44 gram of
carbon dioxide
and
2.7 gram of
H2O SHOW THAT
the reaction
obeys
law of
conservation of mass
so you have to prove
this reaction follows the law of conservation of mass
 
so we need to write a reaction
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
