Q1. In the following reactions: (1) 2SO2 + O2 ⇌ 2SO3 (2) N2 + 3H2 ⇌ 2NH3 (3) N2 + O2 ⇌ 2NO (4) H2 + I2 ⇌ 2HI Which reactions occur in the presence of a catalyst?
A I and III
B II and IV
C I and II Correct
D I, II and III
Explanation
The oxidation of sulphur dioxide to sulphur trioxide in the Contact process uses a catalyst, commonly vanadium pentoxide. The combination of nitrogen and hydrogen to form ammonia in the Haber process also needs a catalyst, commonly iron. The direct combination of nitrogen and oxygen to form nitric oxide is favoured at very high temperature and is not the standard catalytic equilibrium asked here. Hydrogen and iodine forming hydrogen iodide is a reversible reaction normally discussed without requiring a catalyst in this comparison.