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 that has a lower activation energy. This means that more reactant particles have sufficient energy to collide and form products in a given time.

Scientists can predict the effects of changing conditions on the position of an equilibrium in a closed system. This includes how changes in concentration, temperature, or pressure will affect the yield of reactants and products.

A reversible chemical reaction reaches equilibrium when the rates of the forward and reverse reactions are equal. This occurs in a closed system where reactants and products are neither added nor removed, allowing them to stabilize at a constant concentration.

Increasing the pressure on the system will increase the yield of ammonia. This is because the reaction produces fewer moles of gas on the right-hand side (2 moles of NH3) compared to the left (4 moles: 1 N2 and 3 H2). According to Le Chatelier's Principle, the system will shift to the side with fewer moles.

Increasing the temperature will decrease the yield of ammonia because the forward reaction is exothermic. As a result, the system will shift to favor the endothermic reverse reaction to absorb the added heat, leading to a lower concentration of ammonia.