Question

For the following gases equilibrium $N_2{O}_4\left(g\right)\rightleftharpoons 2N{O}_2\left(g\right)$
$K_P$ is found to be equal to $K_C$. This is attained when :

• A. $0^{o}C$
• B. $273K$
• C. $1K$
• D. $12.19K$

Answer 1

The correct option is D $12.19K$

$K_c$ and $K_p$ are the equilibrium constants of gaseous mixtures. However, the difference between the two constants is that $K_c$ is defined by molar concentrations, whereas $K_p$ is defined by the partial pressures of the gasses inside a closed system. The equilibrium constants do not include the concentrations of single components such as liquids and solid, and they do not have any units.

The relation between the two constants is given by $K_p=K_c\times {\left(RT\right)}^{\Delta n}$, where $\Delta n$ is (Total moles of gas on the products side) - (Total moles of gas on the reactants side).
Hence in the given question $\Delta n=2-1=1$.
In question,the given condition is $K_p$ is found to be equal to $K_c$
$K_p=K_c\times {\left(0.0821T\right)}^{1}T=\frac{1}{0.0821}=12.19K$