Question

At 298 K, the value of $K_c$ for the reaction A$_2$O$_4$(g) $\rightleftharpoons$ 2AO$_2$(g) is $x$ mol L$^{-1}$. What is the approximate $K_p$ value for this reaction?
Given: $R = 0.082$ L atm mol$^{-1}$ K$^{-1}$

• A. 24.4x
• B. 12.2x
• C. $\dfrac{x}{24.4}$
• D. $\dfrac{24.4}{x}$

Hint:

Use $K_p = K_c(RT)^{\Delta n}$ to convert equilibrium constants between pressure and concentration.

Answer 1

The Correct Option is A

Use the relation: $K_p = K_c(RT)^{\Delta n}$
$\Delta n = 2 - 1 = 1$ (2 moles of gas on product side, 1 on reactant)
$K_p = x \cdot (0.082 \cdot 298)^1 = x \cdot 24.4$