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\mathrm{PCl_{5}}, dissociates as

\mathrm{PCl_{5}(g)\rightleftharpoons PCl_{3}(g) +Cl_{2}(g)}

5 moles of \mathrm{PCl_{5}} are placed in a 200 litre vessel which contains 2 moles of \mathrm{N_{2}}, and is maintained at 600 K. The equilibrium pressure is 2.46 atm. The equilibrium constant \mathrm{K_{p}}, for the dissociation of \mathrm{PCl_{5}} is _______ \mathrm{\times 10^{-3}}. (nearest integer)

(Given: \mathrm{R=0.082 \;L \;atm \;K^{-1}mol^{-1}}: Assume ideal gas behaviour)

Option: 1

1107


Option: 2

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Option: 3

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Option: 4

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Answers (1)

best_answer

\\\mathrm{PCl}_{5} \rightleftharpoons \mathrm{PCl}_{3}+\mathrm{Cl}_{2}\\ \mathrm{P_{\circ }-x}\;\; \; \; \; \mathrm{x}\;\; \; \; \; \; \; \;\; \mathrm{x}

\mathrm{K_{p}=\frac{x^{2}}{P_{0}-x}

Now, initially \mathrm{PCl_5} and \mathrm{N_2} were added to the container. \mathrm{N_2} is inert to the system and will not react under the given conditions

\mathrm{ P_{N_{2}}=\frac{n R T}{V}=\frac{2 \times R \times 600}{200}=6 R}

\mathrm{P_{0}=P _{P C l_{5}}=\frac{n R T}{V}=\frac{5 \times R \times 600}{200}=15 R}

Given,

\mathrm{P_{eq}=P_{0}-x+x+x+P_{N_{2}}}

\begin{aligned} \mathrm{2.46 =P_{0}+x+P_{N_{2}}=15 R+x+6 R} \\ \end{aligned}

\begin{aligned} \mathrm{2.46 =21 R+x} \\ \end{aligned}

\begin{aligned} &\mathrm{x=2.46-21 R=2.46-21 \times 0.082 }\end{aligned}

\mathrm{x=2.46-1.722=0.738}

and,

\begin{aligned} \mathrm{P_{0}-x =15 R-0.738=1.23=0.492} \end{aligned}

Now, \mathrm{K_{p}=\frac{x^{2}}{P_{0}-x}=\frac{(0.738)^{2}}{0.492}=1.107}

\mathrm{K_{p}=1107 \times 10^{-3}}

Hence, the answer is 1107

Posted by

Ritika Kankaria

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