In which of the following reactions heterogeneous catalysis is involved?I -  2SO2(g)+O2(g) →NO2SO3(g)II - 2SO2(g) →Pt(s) 2SO3(g)III -  N2(g)+3H2(g) →Fe(s) 2NH3(g)IV - CH3COOCH3(l)+H2O(l) →HCl(l) CH3COOH(aq)+CH3OH(aq)

Reaction in which catalyst is in different phase than other (reactants and products) is known as heterogeneous catalysis.(ii) 2SO2(g) →Pt(s) 2SO3(g)     Here, reactant SO2 and product SO3 are in gaseous phase while platinum is in solid phase. So, this reaction represents a heterogeneous catalysis.(iii) N2(g)+3H2(g) →Fe(s) 2NH3(g)     Similarly, here, reactant N2 and H2 and product NH3 are in gaseous phase, while Fe is in solid phase. So, this reaction represents a heterogeneous catalysis. Whereas, in other reactions catalyst is in same phase with reactant(s) and product(s).