Answer 1

Given:
Empirical formula  = XY₂
Vapor density  = Empirical formula weight
Molecular formula =?
Molecular weight  = n(Empirical formula weight)

= 2 x V.D.

n(Empirical formula weight) =  2 x V.D.

Since Vapour density Empirical formula weight

 n = 2

Molecular formula  = 2(Empirical formula)

= 2(XY₂)

Molecular formula = X₂Y₄