C6.1.4 - The Contact process

Question 1

What is the Contact process?

Answer 1

Industrial process to make sulphuric acid

Question 2

What are the raw materials needed to make sulphuric acid?

Answer 2

Sulfur, air (a source of oxygen), water

Question 3

In the second stage of the Contact process what the conditions chosen for the reversible reaction?

Answer 3

• a pressure of 2 atmospheres (200 kPa)
• a temperature of 450C
• a vanadium(V) oxide catalyst

Question 4

What happens in the Contact process?

Answer 4

Stage 1: Sulfur burns in air to produce sulfur dioxide
Stage 2: Sulfur dioxide and oxygen react together to produce sulfur trioxide
Stage 3: Sulfur trioxide is converted to sulfuric acid

Question 5

Is the forward reaction in Stage 2 of the Contact process exothermic or endothermic?

Answer 5

Exothermic

Question 6

Is the backward reaction in Stage 2 of the Contact process exothermic or endothermic?

Answer 6

Endothermic

Question 7

Why is the temperature chosen for Stage 2 of the Contact Process a compromise?

Answer 7

It is low enough to achieve a reasonable equilibrium yield, but high enough to achieve a reasonable rate of reaction. In addition, the vanadium(V) oxide catalyst only works above 380C