For a reaction taking place in a container in equilibrium with its surroundings, the effect of temperature on its equilibrium constant in terms of change in entropy is described by
- (A)With increase in temperature, the value of for exothermic reaction decreases because the entropy change of the system is positive
- (B)With increase in temperature, the value of for endothermic reaction increases because unfavourable change in entropy of the surroundings decreases✓ Correct
- (C)With increase in temperature, the value of for endothermic reaction increases because the entropy change of the system is negative
- (D)With increase in temperature, the value of for exothermic reaction decreases because favourable change in entropy of the surroundings decreases✓ Correct
Answer: (B), (D)
Solution
[B] Correct: For an endothermic reaction, . At higher temperature, the unfavorable entropy change of surroundings () becomes less negative (less unfavorable), making more negative and increasing .
[D] Correct: For an exothermic reaction, . At lower temperature, the favorable entropy change of surroundings () is larger. As temperature increases, this favorable contribution decreases, making less negative and decreasing .
[A] Incorrect: The entropy change of the system is not necessarily positive for an exothermic reaction.
[C] Incorrect: The entropy change of the system is not necessarily negative for an endothermic reaction.
[D] Correct: For an exothermic reaction, . At lower temperature, the favorable entropy change of surroundings () is larger. As temperature increases, this favorable contribution decreases, making less negative and decreasing .
[A] Incorrect: The entropy change of the system is not necessarily positive for an exothermic reaction.
[C] Incorrect: The entropy change of the system is not necessarily negative for an endothermic reaction.
JEE Advanced · 2017 · 21 May 2017 · Paper 2 · One or more correct options