Question

For the reaction in equilibrium:
N₂(g) + 3H₂(g) ⇌ 2NH₃(g), ΔH = -Q
Reaction is favoured in forward direction by:

• A. use of catalyst
• B. decreasing concentration of N₂
• C. low pressure, high temperature and high concentration of ammonia
• D. high pressure, low temperature and higher concentration of H₂

Answer 1

The Correct Option is D

According to Le Chatelier's principle, if a change of condition is applied to a system in equilibrium, the system will shift in a direction that relieves the stress. For the given reaction, N₂(g) + 3H₂(g) ⇌ 2NH₃(g), which is exothermic (ΔH = -Q):

High Pressure: The forward reaction produces fewer moles of gas (2 moles of NH₃) than the reactants (4 moles of N₂ and H₂). Increasing the pressure favors the side with fewer moles of gas, shifting the equilibrium towards the formation of ammonia.

Low Temperature: Since the reaction is exothermic, decreasing the temperature favors the forward reaction (heat is treated as a product).

Higher Concentration of Reactants: Increasing the concentration of N₂ or H₂ shifts the equilibrium to the right to consume the added reactant.

A catalyst speeds up both the forward and reverse reactions equally but does not affect the equilibrium position.