Question

What is the law of conservation of mass? If $12g$ of Carbon is burnt in presence of oxygen, how much $C{O_2}$ will be formed?

Answer 1

We need to remember that toms cannot be created or destroyed. Atoms of different elements may combine with each other in fixed, simple, whole number ratios to form compound atoms. Carbon and oxygen combine together to form carbon dioxide; this process is also known as combustion.

Complete answer:
As we know that the law of conversion of masses states that the mass is neither created nor destroyed in a chemical reaction. In simple terms we can say that mass of reactants must be equal to mass of products. For example: In Combustion process there is burning of wood which is a conservation of mass as the burning of wood involves Oxygen, Carbon dioxide, water vapor and ashes. During a chemical reaction, atoms are neither created nor destroyed. The atoms of the reactants are just rearranged to form products. Hence, there is no change in mass in a chemical reaction.
Now it is asked if $12g$ of carbon is burnt in presence of oxygen how much carbon dioxide is formed. So
Total mass of carbon = $12g$
Total mass of oxygen = $32g$
Total mass of carbon dioxide =?
On Applying law of conservation of mass
Total mass of reactant = total mass of product
$C$ + ${O_2}$ = $C{O_2}$
$12g$ + $32g$ = $C{O_2}$
$44g$ = $C{O_2}$

Note:
According to the law of conservation of mass, during any physical or chemical change, the matter is neither created nor destroyed. However, it may change from one form to another. Mass can be calculated as the sum of the relative formula masses of the reactants is equal to the sum of the relative formula masses of the products.