Question

During the production of sulphuric acid by the contact process, the three reactions represented by the equations below occur.

S(l) + O₂(g) → SO₂(g)

2SO₂(g) + O₂(g) → 2SO₃(g)

SO₃(g) + H₂SO₄(l) → H₂S₂O₇(l)

Which of the following statements is true for all three of these reactions?

• A. All occur at elevated pressures to ensure maximum yield.
• B. All take place at high temperatures to increase the reaction rate
• C. All are redox reactions
• D. All are exothermic

Answer 1

The correct option is D

All are exothermic

All are exothermic. 1 and 2 are redox, but 3 is not. High temperatures and pressures are not used for all reactions here. For example, 3 takes place rapidly and completely at room temperature and pressure, so elevated pressures and temperatures are not required.