Question

State and explain laws of chemical combination.

Answer 1

Law of Chemical Combination

$\left(1\right)$ Law of Conservation of Mass

In a chemical change, the total mass remains conserved. i.e. mass before the reaction is equal to mass after the reaction.

$H_2\left(g\right)+{Cl}_2\left(g\right)⟶2HCl$

Mass before reaction=$2+71=73g$

Mass after reaction=$2$x$36.5=73g$

$\left(2\right)$ Law of constant or Definite Proportions

All Chemical compounds are found to have constant composition irrespective of their method of preparation or source.

For g. in water $\left(H_{2}O\right)$, hydrogen and oxygen combine in $2:1$ molar ratio, this ratio remains constant whether it is tap water or river water.

$\left(3\right)$ Law of Multiple Proportions

When one element combines with the other elements to form two or more different compounds, the mass of one element which combines with a constant mass of the other, bear a simple ratio to one another.

For eg. $C$ and $O_2$ reacts together to form $CO$ and ${CO}_2$. Here, fixed mass of carbon $\left(12g\right)$ reacting with different masses of oxygen $(16g$ and $32g)$ . Therefore, ratio of the masses of oxygen has ratio $16:32$ or $1:2$