This question is about catalysts and equilibrium - AQA - GCSE Chemistry Combined Science - Question 6 - 2022 - Paper 2

A catalyst increases the rate of a reaction by providing a different reaction pathway with a lower activation energy. This allows more reactant particles to successfully collide and react, thus increasing the rate of the reaction.

Le Chatelier's Principle allows scientists to predict how changes in conditions, such as concentration, pressure, or temperature, will affect the position of equilibrium in a closed system.

A reversible chemical reaction reaches equilibrium when the forward and reverse reactions occur at the same rate in a closed system, preventing the escape of reactants and products. At this point, the concentrations of reactants and products remain constant.

Increasing the pressure on the equilibrium position of the ammonia reaction favors the side with fewer moles of gas. Therefore, the yield of ammonia increases, as there are fewer moles of gas on the product side (2 moles of NH₃) than on the reactant side (4 moles in total: N₂ + 3H₂).

Increasing the temperature decreases the yield of ammonia because the forward reaction is exothermic. The system shifts in the endothermic direction to absorb the added heat, therefore favoring the reactants over the products at higher temperatures.