Question

Given the following reaction at equilibrium \(N_2(g) + 3H_2(g) \rightleftharpoons 2NH_3(g)\). Some inert gas at constant pressure is added to the system. Predict which of the following facts will be affected.

• A. More \(NH_3(g)\) is produced
• B. Less \(NH_3(g)\) is produced
• C. No effect on the equilibrium
• D. \(K_p\) of the reaction is decreased

Hint:

Adding an inert gas:
At constant \textbf{volume}: no effect on equilibrium
At constant \textbf{pressure}: equilibrium shifts towards side with more gas moles
\(K_p\) remains unchanged (depends only on temperature)

Answer 1

The Correct Option is B

Step 1: When an inert gas is added at constant pressure, the volume of the system increases.
Step 2: Increase in volume leads to a decrease in partial pressures of all reacting gases.
Step 3: According to Le Chatelier’s principle, the equilibrium shifts towards the side with greater number of moles of gas. \[ \text{Left side moles} = 1 + 3 = 4 \] \[ \text{Right side moles} = 2 \]
Step 4: Since the reactant side has more gaseous moles, equilibrium shifts towards the left.
Step 5: As a result, less \(NH_3\) is formed.
Step 6: The equilibrium constant \(K_p\) depends only on temperature and remains unchanged.