Chemistry Equilibrium SZABMU 2022
PMDC Verified Question 52 of 102
For the chemical reaction;
\( \text{N}_{2(g)} + 3\text{H}_{2(g)} \rightleftharpoons 2\text{NH}_{3(g)} + \text{Heat} \)
We can maximize the yield of \( \text{NH}_3 \):
A
By increasing the temperature
B
By decreasing the pressure
C
By increasing the volume of the reaction vessel
D
By continuous withdrawal of ammonia
Tap any option to test your recall and reveal the step-by-step Propolis autopsy.

Propolis Cognitive Error Autopsy

Official Correct Choice:
Option D: By continuous withdrawal of ammonia
Concept:

According to Le Chatelier's Principle, continuously removing a product prevents the system from ever reaching equilibrium, forcing the forward reaction to proceed indefinitely.

Formula:

$$ Q_c = \frac{[\text{NH}_3]^2}{[\text{N}_2][\text{H}_2]^3} $$

Solution:

  • If \( \text{NH}_3 \) is continuously withdrawn from the vessel, its concentration drops to near zero.


  • This makes the reaction quotient \( Q_c \) practically zero, which is far less than \( K_c \).


  • To try and restore \( K_c \), the reactants will continuously convert into more product.


Why other options are incorrect:

Increasing temperature shifts this exothermic reaction backwards. Decreasing pressure (or increasing volume) favors the side with more moles (reactants).

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