Question

For which of the following reaction, $K_{p}=K_{c}$ ?

• A. $2 \mathrm{NOCl}(\mathrm{g}) \rightleftharpoons 2 \mathrm{NO}(\mathrm{g})+\mathrm{Cl}_2(\mathrm{~g})$
• B. $\mathrm{N}_2(\mathrm{~g})+3 \mathrm{H}_2(\mathrm{~g}) \rightleftharpoons 2 \mathrm{NH}_3(\mathrm{~g})$
• C. $\mathrm{H}_2(\mathrm{~g})+\mathrm{Cl}_2(\mathrm{~g}) \rightleftharpoons 2 \mathrm{HCl}(\mathrm{g})$
• D. $\mathrm{PCl}_3(\mathrm{~g})+\mathrm{Cl}_2(\mathrm{~g}) \rightleftharpoons \mathrm{PCl}_5(\mathrm{~g})$

Answer 1

Answer: (C)

$\mathrm{K}_{\mathrm{p}}=\mathrm{K}_{\mathrm{c}} \times(\mathrm{RT})^{\Delta \mathrm{n}_{(\mathrm{g})}}$

$\Delta n _{( g )}=$ Sum of gaseous products $-$ Sum of gaseous reactants $K _{ p }= K _{ c }$ when $\Delta n _{( g )}=0$

$\Delta n _{( g )}=2-2=0$

So the correct option is $H _{2}( g )+ Cl _{2}( g ) \rightleftharpoons 2 HCl ( g )$

In rest other options $K _{ p }$ and $K _{ c }$ can not be equal as $\Delta n _{( g )}$ is not zero.