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 Y is 5 and the compound has a vapour density (V.D.) 25, find its molecular formula.

Answer 1

Empirical formula = X₂Y

Atomic weight (X) = 10

Atomic weight (Y) = 5

Empirical formula weight = (2 × 10) + 5 = 25

n = `"Molecular weight"/"Empirical formula weight"`

= `[2 xx "V.D."]/"Empirical formula weight"`

= `[ 2 xx 25]/25`

= 2
∴ Molecular formula = X₂Y × 2

= X₄Y₂