Question

For calculating the percentage composition of compound its molecular weight must be known. Give reason

Answer 1

For calculating the percentage composition of a compound, its molecular weight must be known.

1) Let us first understand what is percentage composition of a compound. Percentage composition of a compound is the amount of each element present in a compound with respect to the total weight of the compound, multiplied by 100.

2) Therefore, molecular weight of the compound forms the basis for calculating its percentage composition.

3) It can calculated using the formula: (mass of element in the compound/ molecular mass of the compound) × 100 %

4) This can be better understood with the help of an example.

H2O has a molecular weight of 18 g. It has two atoms of hydrogen and one atom of oxygen. Now, the percentage composition of H2O is,

% of hydrogen = (2/18) × 100 % = 11.19 %

% of oxygen = (16/18) × 100 % = 88.81 %

Thus, the molecular weight of a compound must be known to calculate its percentage composition.