Question
Chemistry Question on Law Of Chemical Equilibrium And Equilibrium Constant
For the reaction in equilibrium:
N2(g) + 3H2(g) ⇌ 2NH3(g), ΔH = -Q
Reaction is favoured in forward direction by:
use of catalyst
decreasing concentration of N2
low pressure, high temperature and high concentration of ammonia
high pressure, low temperature and higher concentration of H2
high pressure, low temperature and higher concentration of H2
Solution
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, N 2(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 N 2 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 N 2 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.