Question

A and $B$ are two identical vessels. A contains $45g$ ethane at $1$ atm and $298K.$ The vessel $B$ contains $225g$ of gas $X_{2}$ at same temperature and pressure. The vapour density of $X_{2}$ is:-

• A. $150$
• B. $75$
• C. $45$
• D. $37.5$

Answer 1

Answer: (B)

Both containers have same volume
$P=1atm$
$T=298K$
$PV=n_{A}RT\left(P_{A} = P_{B}\right)=1atm$
$PV=n_{B}RT\left(V_{A} = V_{B}\right)=V$
$n_{A}=n_{B}T=298$
Number of moles of $A=$ no of moles of $B$
$\left(\frac{45}{30}\right)_{\text{ethane }}=\left(\frac{225}{M_{0} wt}\right)_{B}$
Mol. wt. of $B=\frac{225 \times 30}{45}=150$
V.D. of $B=\frac{Molwt .}{2}=\frac{150}{2}=75$