Question

A one-litre vessel containing $0.015$ moles of $N _{2( g )}$ and $0.02$ moles of $PCI _{5( g )}$ are heated at $227^{\circ} C$, where the total pressure was found to be $1.843 atm$. Assuming nitrogen to be inert, determine $K _{ p }$ for the following decomposition reaction:
$ PCl _{5( g )} \rightleftharpoons PCl _{3( g )}+ Cl _{2( g )} $
(Put your answer by multiplying with 100 )

Answer 1

$ n _{\text {Total }}=\frac{ PV }{ RT }=\frac{1.843 \times 1}{0.082 \times 500}=0.045 $
$ n _{ N _2}=0.015 \Rightarrow n \left( PCl _5+ PCl _3+ Cl _2\right)=0.03 $
$ \begin{array}{ccc} PCl _{5( g )} & \rightleftharpoons PCl _{3( g )} & + Cl _{2( g )} \\ 0 \cdot 02- x & x & x \end{array} $
$0.02+x=0.03 \therefore x=0.01$ mole
$ X _{ PCl _3}=\frac{0.01}{0.045\left( n _{\text {Total }}\right)}=\frac{2}{9}= X _{ Cl _2} $