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 $B=\frac{Molwt.}{2}=\frac{150}{2}=75$