Question

Vapour density of a volatile substance is 4 times the vapour density of methane. Its molecular mass is:

• A. 8
• B. 2
• C. 64
• D. 128

Answer 1

The correct option is C 64

Vapur density of given by the formula:

$V.D.=\frac{Mgas}{2}$

Vapour density of methane $=\frac{16}{2}=8$

Vapour density of gas $=4\times 8=32$

$\therefore M_{gas}=32\times 2$

$i.e.M_{gas}=64g/mol$

Hence, option $C$ is correct.