Ncert Exercises & Solutions

In which of the following reactions heterogeneous catalysis is involved ?

$(i) 2 S O_{2} (g) + O_{2} (g) \overset{N O (g)}{\to} 2 S O_{3} (g)$

$(i i) 2 S O_{2} (g) \overset{P t (s)}{\to} 2 S O_{3} (g)$
$(i i i) N_{2} (g) + 3 H_{2} (g) \overset{F e (s)}{\to} 2 N H_{2} (g)$
$(i v) C H_{3} C O O C H_{3} (l) + H_{2} O (l) \overset{C H (l)}{\to}$
$C H_{3} C O O C H (a q) + C H_{3} O H (a q)$