Question

For the reaction
$2{NO}_2\left(g\right)\rightleftharpoons 2NO\left(g\right)+O_2\left(g\right)$
$K_c=1.8\times {10}^{-6}$ at ${184}^{o}C$
$R=0.0831kJ{K}^{-1}{mol}^{-1}$
when $K_p$ and $K_c$ are compared at ${184}^{o}C$ it is found that:

• A. $K_p$ is greater than $K_c$
• B. $K_p$ is less than $K_c$
• C. $K_p=K_c$
• D. Whether $K_p$ is greater than, less than or equal to $K_c$ depends upon the total gas pressure

Answer 1

The correct option is A $K_p$ is greater than $K_c$

For the reaction
$2{NO}_2\left(g\right)\rightleftharpoons 2NO\left(g\right)+O_2\left(g\right)$
$K_c=1.8\times {10}^{-6}$ at ${184}^{o}C$
$R=0.0831kJ{K}^{-1}{mol}^{-1}$
when $K_p$ and $K_c$ are compared at ${184}^{o}C$ it is found that
$K_p$ is greater than $K_c$
$K_p=K_c{\left(RT\right)}^{\Delta n}$
$\Delta n=(2+1)-2=1$
$K_p=K_c{\left(RT\right)}^1$
$K_p=K_c\left(RT\right)$
$K_p>K_c$ as $\left(RT\right)=0.0831kJ{K}^{-1}{mol}^{-1}\times (184+273)K=38>1$