Question

The imprical formula of a compound is CHO2 and its V.D is 45 then find its molecular formula

Answer 1

Answer:

Molecular formula = C₂H₂O₄

Explanation:

We know that,

Vapour Density = $\dfrac{Molecular \ mass}{2}$

Hence,

Molecular mass = Vapour density * 2

Also,

n(Empirical formula) = Molecular formula

Here,

n = $\dfrac{Molecular \ formula \ mass}{Empirical \ formula \ mass}$

Given that,

Vapour Density = 45

Empirical formula = CHO₂

Therefore,

Empirical formula mass = 12 + 1 + 16*2

                                       = 45 g

Substituting value of vapour density in Molecular mass = Vapour density * 2 we get,

Molecular mass = Vapour density * 2

Molecular mass = 45 * 2

Molecular mass = 90 g

Therefore,

n = $\dfrac{Molecular \ formula \ mass}{Empirical \ formula \ mass}$

n = $\dfrac{90}{45} = 2$

Hence,

Molecular Formula = 2 * (Empirical Formula)

Molecular Formula = 2 * (CHO₂)

Molecular Formula = C₂H₂O₄