The Question is from neet-chemistry chemical-equilibrium , and it was created by the author Mr. S M HUSSAIN

Question

Consider the endothermic reaction: $N_2O_4(g) \rightleftharpoons 2NO_2(g)$. A sealed container filled with an equilibrium mixture of $N_2O_4$ and $NO_2$ is suddenly immersed in an ice bath. Which of the following changes will occur initially?

Mr. S M HUSSAIN · Accepted Answer

## CORE INFORMATION
✓ **Answer**: B
## CONCEPT FRAMEWORK
 **Primary Concept**: Le Chatelier's Principle
 **Related Topics**: Equilibrium, Endothermic reactions, Exothermic reactions
 **Prerequisites**: Understanding of equilibrium shifts in response to changes in temperature and pressure.
## SOLUTION PATHWAY
**Given Information**:
  * Reaction: $N_2O_4(g) ightleftharpoons 2NO_2(g)$ (endothermic)
  * System at equilibrium
  * Temperature decrease (ice bath)
**Method & Steps**:
 1. Identify the type of reaction:
  Reasoning: The reaction is endothermic, meaning it absorbs heat.  We can represent this as: $N_2O_4(g) + heat ightleftharpoons 2NO_2(g)$
 2. Apply Le Chatelier's principle:
  Reasoning: Le Chatelier's principle states that if a change of condition is applied to a system in equilibrium, the system will shift in a direction that relieves the stress.
  Working: Decreasing the temperature (removing heat) stresses the system. To relieve this stress, the equilibrium will shift to the left, favoring the exothermic direction (heat-releasing).
 3. Determine the initial change:
  Reasoning: Shifting to the left means consuming $NO_2$ and producing $N_2O_4$.
  Result: The concentration of $N_2O_4$ will initially increase, and the concentration of $NO_2$ will initially decrease.
  Verification: This shift towards reactants is consistent with Le Chatelier's principle's response to a decrease in temperature for an endothermic reaction.
 ## OPTION ANALYSIS
[A] :x: The concentration of $NO_2$ decreases initially, not increases.
[B] ✓: The concentration of $N_2O_4$ increases initially as the equilibrium shifts to the left to compensate for the reduced temperature.
[C] :x: The equilibrium constant ($K_c$) is temperature-dependent.  While it will change, this is not the initial change observed; the concentrations adjust first.
[D] :x: A change in temperature will inevitably disturb the equilibrium, leading to a shift.
 ## LEARNING AIDS
 **Common Mistakes**:
  1. Confusing endothermic and exothermic reactions: Remember that endothermic reactions absorb heat, while exothermic reactions release heat.
  2. Incorrect application of Le Chatelier's principle:  Always consider which direction the equilibrium shifts to relieve the applied stress.
 **Quick Tips**:
  1. Think of heat as a reactant or product in endothermic and exothermic reactions respectively to apply Le Chatelier's principle easily.
  2. Visualize the equilibrium shifting to counteract the change in temperature.

Mr. S M HUSSAIN · Answer

The concentration of $NO_2$ increases.

Mr. S M HUSSAIN · Answer

The correct Option is "The concentration of $N_2O_4$ increases."

Mr. S M HUSSAIN · Answer

The equilibrium constant ($K_c$) increases.

Mr. S M HUSSAIN · Answer

No change occurs.

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