JAMB Chemistry 2024 Paper

Firstly, Relative Molecular mass = 2 x Vapour Density

The challenge is to find the relative molecular mass = Molar mass of the gas

But we were given V = 560cm$^{3}$ , Molar Volume = 22.4 dm$^{3}$ = 22400cm$^{3}$ and Mass = 0.4g

However, we can obtain the value for Number of moles, then easily obtain the value for our Molar mass, using mass given.

⇒ n = $\;\frac{V}{M.V}$ = $\;\frac{560}{22400}$ = 0.025 mole

Also, n = $\;\frac{m}{M}$

M = $\;\frac{m}{n}$ = $\;\frac{0.4}{0.025}$ = 16.0

Recall that Molar mass of gas = 2 x V.D

Therefore, V.D = $\;\frac{16.0}{2}$ = 8.0