The Haber process template

Ammonia synthesis for GCSE, A-level and NCERT: plant flow (feed gases, compressor, iron-catalyst converter, condenser, recycle), the equations with ΔH = −92 kJ mol⁻¹, Kp, and why 450 °C and 200 atm are a compromise between yield (Le Chatelier) and rate and cost.

What the template shows

• N₂(g) + 3H₂(g) ⇌ 2NH₃(g), ΔH = −92 kJ mol⁻¹: iron catalyst, about 200 atm and 450 °C, with the unreacted gases recycled
• Plant flow
• Feed gases
• N₂ from liquid air
• H₂ from natural gas
• beds of iron catalyst
• gases cooled:
• Liquid ammonia
• run off and stored
• under pressure
• unreacted N₂ + H₂ recycled (≈ 15% converted per pass)
• Choosing the conditions
• ΔH = −92 kJ mol⁻¹ (−46 kJ per mole of NH₃) · 4 mol of gas → 2 mol of gas
• steam reforming of natural gas, Ni catalyst, ≈ 800 °C
• shift reaction: more H₂; CO₂ is then removed
• Equilibrium constant
• Kp falls as T rises (exothermic); pressure and the catalyst do not change Kp.
• Equilibrium yield of NH₃
• Higher at low T (forward reaction exothermic)
• Faster at high T
• Higher at high p (4 mol → 2 mol gas)
• Faster at high p
• ≈ 200 atm: limited by cost and safety
• Faster; equilibrium reached sooner

Drawn with 37 shapes – every one editable in MolDraw.

Sources

• Housecroft & Sharpe, Inorganic Chemistry, 5th ed., Pearson 2018, ch. 15 Textbook
• Atkins, de Paula & Keeler, Atkins' Physical Chemistry, 11th ed., OUP 2018, ch. 6 Textbook
• NCERT, Chemistry Part I, Class XI, ch. 6 Equilibrium Textbook