6.1.2 haber process

• Plants need nitrogen to produce proteins (for growth)

  • cannot absorb nitrogen from the air
  • soluble nitrates are absorbed through the roots
  • nitrates re-enter the soil when plants decompose
  • harvesting crops takes the nitrogen out of the system, so farmers should manually add nitrogen back to the soil
• Plants remove carbon dioxide from the atmosphere and provide us with a food source
• Uses of ammonia:

  • fertiliser
  • explosives
• N2+3H2 ⇌ 2NH3

  nitrogen + hydrogen ⇌ ammonia
• Using a low temperature will give high yield, slow rate

  Using a high temperature will give a low yield, high rate

  A compromise temperature between rate and yield is used
• Using high pressure will give high yield and fast rate but it is dangerous and expensive (thicker pipes)
• Any temperature below 450 degrees celsius would give the highest yield

  Any pressure higher than 200 atmospheres would give the highest yield

  Lower temp = slower rate of reaction

  450 degrees celsius is a compromise between rate and yield

  Higher pressures are too dangerous/safety risk, also more expensive