Question

A compound exists in the gaseous state both as a monomer $\left(A\right)$ and dimer $\left(A_2\right)$. The molecular weight of the monomer is $48$. In an experiment, $96$ g of the compound was confined in a vessel of volume $33.6$ litres and heated to ${273}^0$C. Calculate the pressure developed, if the compound exists as a dimer to the extent of $50$ per cent by weight, under these conditions. $(R=0.082)$

Answer 1

$A$ & $A_2$ are two states in gaseous phase having ratio of $50$% i.e $1:1$ .

$\therefore$ Mole of $A=\frac{96}{2}\times \frac{1}{48}=1$

We know $n=\frac{W}{m}$

$\therefore$ Mole of $A_2=\frac{96}{2}\times \frac{1}{96}=\frac{1}{2}$

Total moles of $A$ & $A_2$ are=$1+\frac{1}{2}=\frac{3}{2}$

$PV=nRT$

$\Rightarrow P\times 33.6=\frac{3}{2}\times 0.0821\times 546$

$\Rightarrow$ Pressure= $2atm$