Question

For the gas phase reaction $2NO\iff N_2+O_2,\Delta H=-43.5kcals$. Which one of the following is true for the reaction?

• A. $K_c$ is independent of temperature
• B. $K_c$ increases as T decreases
• C. $K_c$ decreases as T decreases
• D. $K_c$ varies with the addition of $NO$

Answer 1

Answer: (B)

$K_c$ increases as T decreases

Given fa reaction in gas phase reaction, $2NO\iff N_2+O_2,\Delta H=-43.5Kcals$

The negative value of enthalpy of the reaction indicates that it is an exothermic reaction. When temperature is lowered, the reaction will proceed in the forward direction so as to liberate heat and nullify the effect of lowering temperature. This will increase the value of the equilibrium constant $K_c$. Hence, option B is the correct answer.