Question

A gas has density $2.5$ $gm/l$ at ${127}^{0}C$ and $1$ atm pressure, the molecular weight of a gas is:

• A. $78$
• B. $82.1$
• C. $44$
• D. $64$

Answer 1

Answer: (B)

$82.1$

$PV=nRT$

$\Rightarrow P=\frac{n}{V}RT=\frac{W}{MV}RT$

$=\frac{d}{M}RT$

$\therefore$ $P=\frac{d}{M}RT\Rightarrow M=\frac{dRT}{P}$

$\Rightarrow M=\frac{2.5gm/lit\times 0.0821Lit-atm/K-mol\times 400K}{1atm}$

$\Rightarrow M=82.1gm/mol$

Hence, option $B$ is correct.