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)+ 3 H2(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),