Question

At $273K$, the density of a certain gaseous oxide at $2atm$ is same as that of dioxygen at $5atm$. The molecular mass of the oxide (in $gmo{l}^{-1})$ is:

• A. $80$
• B. $64$
• C. $32$
• D. $160$
• E. $70$

Answer 1

The correct option is A $80$

We know that

$pV=nRT=\frac{w}{M}RT$

$pM=\frac{w}{v}RT$

$pM=dRT$

or $d=\frac{pM}{RT}$

$\because R$ and $T$ are constant and $d_1=d_2$

$\therefore p_1{M}_1=p_2{M}_2$

$2\times M_1=5\times 32$

$M_1=\frac{5\times 32}{2}=80gmo{l}^{-1}$.