Question

Calculate $\%$ composition of underlined atom.
$H_2\underset{–}{O}=$ __________$\%$.

Answer 1

The molar mass of Oxygen = 16.00 x 1 = 16 g/mole

Hydrogen = 1.01 x 2 = 2.02 g/mol

Molar mass of $H_{2}O$ = 18.02 g/mol

% composition of oxygen $=\frac{6}{18.02}\times 100=88.79\%$