Answer:
(A) The value of Kc for this reaction increases as temperature increases, because the reaction is endothermic.
Step-by-step explanation:
N₂O₄ ⇌ 2NO₂
colourless reddish-brown
NO₂ is a reddish-brown gas, while N₂O₄ is colourless.
When you cooled the sample to 0 °C, the position of equilibrium shifted to form more N₂O₄, that is, it <em>shifted to the left</em>.
According to <em>Le Châtelier's Principle,</em> when a stress is applied to a system at equilibrium, the system will respond in a way that tends to relieve the stress.
You applied a stress: you removed heat from the system. It responded by shifting in the direction that produces more heat (<em>to the left</em>).
If you consider heat as part of the reaction, the equation must be
N₂O₄ + heat ⇌ 2NO₂
The reaction is endothermic.
Furthermore, since the position of equilibrium shifted in the direction of reactants, the equilibrium constant decreased.
The value of K <em>decreases as the temperature decreases</em>. If we say it the other way, the value of K increases as the temperature increases.
The correct answer is (A) The value of Kc for this reaction increases as temperature increases, because the reaction is endothermic.
(B) and (D) are <em>wrong</em>, because the reaction is endothermic.
(C) is <em>wrong</em>, because the value of Kc decreases as temperature decreases.
