Given below are certain reactions. Identify the reaction for which $K_P
eq K_C$.

Question

Given below are certain reactions. Identify the reaction for which $K_P 
eq K_C$.

Accepted Answer

B. 1. **Relating Kp and Kc**: For any gaseous equilibrium, the pressure-based equilibrium constant $K_P$ and the concentration-based equilibrium constant $K_C$ are connected by the formula below, where $\Delta n_g$ is the change in moles of gas (moles of gaseous products minus moles of gaseous reactants).
$$K_P = K_C(RT)^{\Delta n_g}$$

2. **When are they equal?** Since $(RT)^0 = 1$, $K_P$ equals $K_C$ only when $\Delta n_g = 0$. If $\Delta n_g 
eq 0$, then $K_P 
eq K_C$.

3. **Checking Option A**: $H_2O(g) + CO(g) ightleftharpoons H_2(g) + CO_2(g)$ has 2 moles of gas on each side, so
$$\Delta n_g = 2 - 2 = 0$$
Hence $K_P = K_C$ here.

4. **Checking Option B**: $N_2(g) + 3H_2(g) ightleftharpoons 2NH_3(g)$ has 4 moles of gaseous reactants and 2 moles of gaseous product, so
$$\Delta n_g = 2 - 4 = -2$$
Since $\Delta n_g 
eq 0$, this is the reaction where $K_P 
eq K_C$.

5. **Checking Options C and D**: Both $H_2(g)+I_2(g)ightleftharpoons 2HI(g)$ and $N_2(g)+O_2(g)ightleftharpoons 2NO(g)$ have 2 moles of gas on both sides, so $\Delta n_g = 0$ and $K_P = K_C$ for both.

Hence, the answer is **Option B**.

Given below are certain reactions. Identify the reaction for which KP≠KCK_P \neq K_CKP​=KC​.

Given below are certain reactions. Identify the reaction for which $K_P \neq K_C$ .