Topic 4: Gases, Equilibria and Ammonia

The Harber process
1. Fritz Harber, 1900's
2. Uses the reversible reaction of ammonia- the conditions allow the forward reaction to happen faster than the backward reaction as it is in equilibirum
3. 200 atmospheres, 450 ' C, iron catalyst
Molar volume of gases
1. Avogadro's gas law- 1 mole of any gas at room temperature and normal atmospheric pressure has a volume of 24dm'3
2. using the idea of molar volume we can calculate volumes of gases needed for reactions
  1. e.g. how much methane (CH4) is burned completely in oxygen if 11g of CO2 is produced?
    1. 1. balanced symbol equation, 2. work out number of moles in 11g of CO2, 3. work out molar ratio of methane to CO2,4 . number of moles x molar volume
3. volume (dm'3) = number of moles x molar volume of gas (dm'3)
Reversible reactions
1. A + B <> C + D
2. The products of a reaction will react to give the original reactants back
3. ammonium chloride + HEAT <<>> Ammonia + Hydrogen Chloride
Equilibrium
1. The forward and backward reactions happen at the same rate.
2. decreasing the temperature for the ammonia reaction will result in an increase of the rate of forward reaction because it is exothermic - heats up
  1. 'equilibirum has shifted to the right'
3. increasing pressure results in a higher yield of ammonia as the equilibrium again shifts to the right. This is to expensive, it is done at 200 at
Fertilisers
1. Over-use of nitrate fertilisers leads to Eutrophication
2. contain soluble nitrogen compounds which plants need to make proteins
3. Ammonia is a raw material used to make nitrogenous fertilisers
4. advantages of manmade- easy to store, distribute and handle, produced to match requirements, increase yield of crops
5. disadvantages of over use- high nitrate levels are dangerous in drinking water, eutrophication

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Topic 4: Gases, Equilibria and Ammonia

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