In which of the following reactions heterogeneous catalysis is involved ? 

(i)2SO2(g)+O2(g)→NO(g)2SO3(g)

(ii)2SO2(g)→Pt(s)2SO3(g)
(iii)N2(g)+3H2(g)→Fe(s)2NH2(g)
(iv)CH3COOCH3(l)+H2O(l)→CH(l)
CH3COOCH(aq)+CH3OH(aq)

1.  (ii), (iii)

2.  (ii), (iii) and (iv)

3.  (i), (ii) and (iii)

4.  (iv)

NEETprep Answer: 
(i) Reaction in which catalyst is in a different phase than other (reactants and products) is known as heterogeneous catalysis.

(ii) 2SO2(g)→Pt(s)2SO3(g)
Here, reactant SO, and product SQ, 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 N2 and H2 reactants are in gaseous phase while NH3 is in solid phase. Whereas in other reactions catalyst is in same phase with reactant(s) and product(s),