Question

A compound made up of two elements X and Y has an empirical formula X₂Y. If the atomic weight of X is 10 and that of Y is 5 and the compound has a vapour density 25, find its molecular formula. 

Answer 1

Emp. formula = X₂Y, At. wt. of X = 10, At .wt. of of Y = 5

∴ Empirical formula mass = 2 x 10 + 5 = 25

If Vapour density V.D = 25

Mol.Mass = V.D. x 2 = 25 x 2 = 50 u

n =  \(\frac{Mol.\,Mass}{Emp.\,formula\,mass}\) = \(\frac{50}{25}\) = 2

Mol. formula = Emp. formula x 2 = X₂Y x 2

=  X₄Y₂