A Level Chemistry OCR Practice Exam

Homologous catalysis refers to a reaction in which the catalyst and the reactants are in the same physical state, which is precisely what the correct answer states. This can occur in various contexts, such as in solution or gas phase when both the catalysts and the reactants are liquids or gases. Having the catalyst in the same phase as the reactants typically facilitates interactions, leading to effective catalytic action. This type of catalysis is contrasted with heterogeneous catalysis, where the catalyst is in a different phase from the reactants, which can alter the kinetics and mechanisms of the reaction. Therefore, understanding the phase relationship is crucial in catalysis studies and applications where the efficiency of the reaction can depend significantly on these factors.