A7LAM CSCA ACADEMYCSCA Academy / Chemistry / Experiments and applications
CSCA Chemistry · Lesson 21 of 21Industrial chemistry
Chimie industrielle · الكيمياء الصناعية
▶ Watch the video lesson (A7LAM students)
Industry picks conditions that give a good yield at a good speed and a reasonable cost. Ammonia synthesis is the classic example.
Key ideas
- Haber process: N₂ + 3H₂ ⇌ 2NH₃, exothermic.
- Conditions: about 400–500 °C, 10–30 MPa, iron catalyst; unreacted gases are recycled.
- Contact process: 2SO₂ + O₂ ⇌ 2SO₃ (V₂O₅ catalyst); SO₃ is then turned into H₂SO₄.
- Chlor-alkali: electrolysis of brine gives NaOH, Cl₂ and H₂.
Formulas to know
- N₂ + 3H₂ ⇌ 2NH₃ (ΔH < 0)
- 2NaCl + 2H₂O → 2NaOH + H₂↑ + Cl₂↑ (electrolysis)
- 4NH₃ + 5O₂ → 4NO + 6H₂O (Pt catalyst)
Worked example
Ammonia synthesis is exothermic. Why run it at about 450 °C rather than a low temperature?
- Yield: a low temperature favours NH₃ (exothermic)
- Rate: but at low temperature the reaction is far too slow
- Compromise: about 450 °C with an iron catalyst
Answer: A compromise between rate and yield
Practice questions
1. High pressure in the Haber process:
favours NH₃ (fewer gas moles) ✓ · lowers the rate · has no effect · favours N₂
4 moles of gas → 2.
2. Products at the cathode in brine electrolysis:
Cl₂ · H₂ and NaOH ✓ · O₂ · Na
Water is reduced to H₂, leaving OH⁻.
3. The iron catalyst in the Haber process:
increases the yield · helps reach equilibrium faster ✓ · is used up · changes ΔH
Catalysts do not shift equilibria.