King of Chemicals Factory
Master the Contact Process steps
What this lesson covers
Why it matters
Sulphuric acid is the king of chemicals, powering everything from car batteries to fertilizers. But you can't just mix sulphur and water; you must build it step-by-step in a factory.
Predict first
Why do we absorb SO₃ gas into concentrated H₂SO₄ instead of directly into water?
Direct absorption creates a fine mist of H₂SO₄ that is hard to condense and dangerous. Absorbing into conc. H₂SO₄ forms oleum (H₂S₂O₇), which is then safely diluted.
- Water reacts too violently, creating a dangerous mist of acid droplets — correct
- SO₃ does not dissolve in water
- Concentrated acid is cheaper than water
- Water would dilute the acid too much immediately
What you do
Balance the factory line: S + O₂ → SO₂, then 2SO₂ + O₂ → 2SO₃ over V₂O₅, absorb with SO₃ + H₂SO₄ → H₂S₂O₇, and finally H₂S₂O₇ + H₂O → 2H₂SO₄.
Check yourself
What is the catalyst used in the conversion of SO₂ to SO₃?
Vanadium(V) oxide is the standard industrial catalyst because it is efficient and resistant to poisoning.
Which equation represents the formation of oleum?
Oleum (pyrosulphuric acid, H₂S₂O₇) is formed by dissolving SO₃ in concentrated H₂SO₄.
Why is the reaction S + O₂ → SO₂ carried out with heat?
Burning sulphur needs heat only to ignite it and provide the activation energy; the combustion itself is exothermic and produces SO₂.
- Vanadium(V) oxide (V₂O₅) — correct
- Iron filings
- Platinum
- No catalyst is needed
- SO₃ + H₂O → H₂SO₄
- SO₃ + H₂SO₄ → H₂S₂O₇ — correct
- 2SO₂ + O₂ → 2SO₃
- S + O₂ → SO₂
- To provide activation energy for combustion — correct
- To melt the sulphur into a liquid for storage
- To increase the yield of SO₃ directly
- To remove impurities from the air