Question

A compound with empirical formula AB₂ has the vapour density equal to its empirical formula weight. Find its molecular formula.

Answer 1

Now since the empirical formula is equal to vapour density and we know that vapour density is half of the molecular mass i.e. we have n = 2 so, the molecular formula is A₂B₄.

Answer 2

Empirical formula of the given compound = AB₂

As we know, Vapour density = Empirical formula weight

∴ Molecular weight = 2 x vapour density

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

= `(2 xx"vapour density")/"vapour density"` 

= 2

∴ Molecular formula = A₂B₄