Question

A compound having empirical formula X₂ Y is made of two elements X and Y. Find its molecular formula. If the atomic weight of X is 10 and that of Y is 5 and the compound has a vapour density 25. 

Answer 1

Empirical formula =X₂ Y, Empirical mass = 2 x 10 + 5 = 25

Vapour density of X₂ Y = 25

Molecular weight of X₂ Y = 2 x vapour density = 2 x 25 = 50

Now molecular weight =n x empirical weight = 50 = n x 25

n = 50/25 = 2

Molecular formula = n x Empirical formula = 2x X₂ Y = X₄ Y₂