Question

A compound exists in the gaseous phase both as monomer $\left(A\right)$ and dimer $A_2$. The molecular weight of $A$ is $48$. In an experiment $96g$ of compound was confined in vessel of volume $33.6L$ and heated to ${273}^{o}C$. Calculate the pressure (in $\text{atm}$ developed if the compound exists as dimer to the extent of $50\%$ by weight under these conditions.

Answer 1

Since $A$ and $A_2$ are two states in gaseous phase having their weight ratio $50\%$ i.e., $1:1$
$\therefore \text{Mole of A}=\frac{96}{2}\times \frac{1}{48}=1$
$\text{Moles of}{A}_2=\frac{96}{2}\times \frac{1}{96}=\frac{1}{2}$
$\therefore ,\text{Total moles of A and}{A}_2\text{are}=1+\frac{1}{2}=\frac{3}{2}$
Thus from
$PV=nRT$
$P\times 33.6=\frac{3}{2}\times 0.0821\times 546$
$P=2\text{atm}$