Nitrogen and hydrogen atoms combine in the ratio 14 : 3 by mass to form ammonia molecule. Find the formula of ammonia molecule by calculating the molar ratio. [Given atomic mass of N = 14 u and H = 1 u]

Number of nitrogen atom present in molecule = Proportion of mass / Ratio of mass = 14/14 = 1

Number of hydrogen atom present in molecule = Proportion of mass / Ratio of mass = 3/1 = 3

This means the number of nitrogen and hydrogen atoms combine in ratio = 1:3

Thus, the formula of molecule of ammonia is $N{ H }_{ 3 }$.