Question

At STP, 5.6 litre of a gas weighs 60 g. The vapour density of gas is:

• A. 60
• B. 120
• C. 30
• D. 240

Answer 1

The correct option is B 120

At STP,

1 mole of gas has volume 22.4 L

then no of moles in 5.6 L gas will be $\frac{5.6}{22.4}=0.25$moles

If 0.25 moles of gas weighs 60 g

then 1 mole of gas weighs$=\frac{60}{0.25}=240g$

Molar mass$=240g$

Molar mass$=2\times Vapourdensity$

$240=2\times V.D$

$\Rightarrow V.D=120$

Hence, the correct option is $\left(B\right)$.