Ch 10 Ammonia

• Why should red litmus paper be damp when testing for ammonia gas?

  So ammonia gas ionises when in contact with the damp red litmus paper to turn it from red to blue
• What is a reversible (chemical) reaction?


  reversible reaction can go both forward and backward at the same time
• How is hydrogen gas obtained for the Haber process?

  from breaking down of crude oil fractions
• How is nitrogen gas obtained for the Haber process?

  from fractional distillation of liquid air
• What is the equation for the Haber process?

  nitrogen + hydrogen <- -> ammonia
• What is the forward reaction of N2 (g) + 3H2 (g) <--> 2NH3 (g)?

  reactant(s) = N2 (g) + 3H2 (g)

  product(s) = 2NH3 (g)
• What is the backward reaction of N2 (g) + 3H2 (g) <--> 2NH3 (g)?

  reactant(s) = 2NH3 (g)

  product(s) = N2 (g) + 3H2 (g)
• How does the forward reaction of the Haber Process start?

  At room temperature; Nitrogen gas unreactive

  -> forward reaction does not take place

  High pressure and relatively high temperature required to start forward reaction between nitrogen and hydrogen

  Iron added as catalyst
• Reversible reaction -> some ammonia produced may break down and decompose back into nitrogen and hydrogen
• What is the effect of pressure on ammonia yield?

  Higher pressure leads to higher ammonia yield and faster reaction

  maintaining high pressure incurs large cost -> as it requires expensive equipment

  and large amount of electricity

  Compromise pressure of 250 atm
• What is the effect of temperature on yield of ammonia?

  lower temperature leads to higher yield of ammonia

  -> as it decreases decomposition of ammonia

  lower temperature slows down reaction

  -> compromise temperature of 450 degrees Celsius
• What is the purpose of a catalyst?

  reaction slow despite high pressure and relatively high temperature

  iron catalyst added to speed up process
• What are the optimal conditions for the Haber process?

  pressure of 250 atm

  Temperature of 450 degrees celsius

  pressure of finely-divided iron catalyst
• Heated on hydrated copper (II) sulfate


  Colourless droplets formed on inner walls of test tube -> Hydrated SuSO4 decomposed upon heating to form water and anhydrous CuSO4

  Colour change from blue crystals to white

  Forward reaction: Heat

  Backward reaction: Add water
• Heated ammonium chloride

  White solid becomes gas upon heating and cools at top part of test tube, forming white solid

  Forward reaction: Thermal decomposition

  Backward reaction: cooling