Question

$2.8g$ of a gas at $1atm$ and $273K$ occupies a volume of $2.24$ litres. The gas can not be:

• A. $O_2$
• B. $CO$
• C. $N_2$
• D. $C_2{H}_4$

Answer 1

The correct option is A $O_2$

Let the molecular weight of gas be M.

Weight of gas $=2.8g$

no. of moles of gas, $\left(n\right)=\frac{\text{wt.}}{\text{mol. wt.}}=\frac{2.8}{M}$

Pressure, $\left(P\right)=1atm$

Volume, $\left(V\right)=2.24L$

Temperature, $\left(T\right)=273K$

$R=0.082Latm{mol}^{-1}{K}^{-1}$

From ideal gas equation,

$PV=nRT$

$\Rightarrow 1\times 2.24=\frac{2.8}{M}\times 0.082\times 273$

$\Rightarrow M=\frac{62.68}{2.24}$

$\Rightarrow M=27.98g\approx 28g$

Hence the molecular mass of gas must be 28 g.

Since molecular mass of $O_2$ is 32 g, hence the gas cannot be $O_2$.