Law of chemical combination Formula
A chemical reactions in a process in which one or more substances that is reactant chemically combine together and converted to one or more new substance that is product.
Example: Reactant A and B chemically react together or chemically combine together and form a compound AB that is new product.
The combination of elements to form compound governed by following laws which is proposed by two scientists Lavoisier and joseph L. Proust.
I) Law of conservation of Mass.
II) Law of constant proportion.
Law of conservation of Mass
Antoine Lavoisier gave the first law of chemical combination That is law of conservation of mass in 1789.
“The law of conservation of mass means that in chemical reactions the total mass of products is equal to the total mass of the reactant . There is no change of mass during the chemical reactions.”
Antoine Lavoisier state that “Mass can neither be created nor be destroyed.”
Formula:
Total mass of reactant = Total mass of product
- When sodium hydroxide react with hydrochloric acid to give new products that is common salt (sodium chloride) and water.
Question:
What mass of silver nitrate will react with 5.85 g of sodium chloride to produce 14.35 g of silver chloride and 8.5 g of sodium nitrate if the law of conservation of mass is true?
Silver nitrate + sodium chloride —-> silver chloride + sodium nitrate
Sodium chloride= 5.85g
Silver chloride. = 14.35g
Sodium nitrate. = 8.5g
Silver nitrate. =. ? (X)
Formula
Total mass of reactant = Total mass of product
X. +. 5.85. =. 14.35. +. 8.5
X. +. 5.85. =. 22.85
X. =. 22.85. – 5.85
X. =. 17 g
Law of constant proportion
The law was proposed by a French chemist joseph L. Proust.
Law State:
In a chemical substance elements are always in fixed proportion by mass.
“A chemical compounds always found to be made up of same elements chemically combine together in the same fixed proportion by mass”.
Similarly in any chemical substance the elements present are always in fixed proportion by mass so that’s why its is also called law of definite proportion.
Example of ammonia :
If we decomposed ammonia by any means say by extreme heat or some other way, then we get the nitrogen and hydrogen atoms in the same proportions by mass.
If we take 17gm of ammonia and decomposed it then we will get 14gm Nitrogen and 3 gm Hydrogen. So we can say Nitrogen and Hydrogen are present in ammonia , in a constant ratio 14:3.
If we decomposed ammonia in other way the ratio of Nitrogen and Hydrogen in the compound will always be the same 14:3.
Question:
Calculate the ratio of water molecule?
In the water molecule 2 atom of hydrogen and one atom of oxygen are present
So ratio of water molecule (H2O)is calculate by following procedure
2×H/O. .
=2×1/16
=2/16
=1/8
So by the above procedure the ratio of water molecule is 1:8