Nitrogen & the chemical industry and food

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Nitrogen Chemistry

Nitrogen exists as a diatomic atom, N2, which has a triple bond so nitrogen is very unreactive.
  • Ammonia is formed between nitrogen and hydrogen, with each N atom forming covalent bonds by sharing one of its electrons to each H atom- this leaves a lone pair of electrons on the N.
  • Ammonia can form hydrogen bonds with water- this makes it very soluble in water.
  • The lone pair on the N atom means ammonia can form dative covalent bonds- can act as a ligand to form complex ions with transition metals.
  • Ammonia can behave as a base too because of the lone pair- molecule forms a dative covalent bond with protons to form the ammonium ion (NH4+)
  • Nitrogen can also form several oxides- NO is nitrogen monoxide, nitric oxide or nitrogen (ll) oxide- it is a colourless gas.
  • N2O is dinitrogen monoxide, nitrous oxide or nitrogen (l) oxide- it has a sweet smell and is also a colourless gas.
  • NO2 is called nitrogen dioxide or nitrogen (V) oxide- it is a brown gas which has a sharp odour and is toxic.
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Nitrogen oxidation states

Form                             Formula           Oxidation state          What produces this form of N2

Nitrogen from the air         N2(g)                    0                             Denitrifying bacteria

Ammonium ions in soil     NH4+(aq)             -3                            Bacteria/microorganisms in soil

Nitrate(V) ions in soil        NO3-(aq)             +5                    Nitrifying bacteria in soil/root nodules

Nitrate(lll) ions in soil        NO2-(aq)             +3                   Nitrifying bacteria in soil/root nodules

Nitrogen(ll) oxide              NO(g)                  +2   Thunderstorms, car engines, denitrifying bacteria

Nitrogen(V) oxide             NO2(g)                +4                Oxidation of NO in atmosphere

Nitrogen(l) oxide              N2O(g)                +1                   Denitrifying bacteria in soil  

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The Nitrogen cycle

(http://anthony.darrouzet-nardi.net/works/nitrogenbiochemistry.jpg)

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The Nitrogen cycle cont.

Reduction/Oxidation in the cycle:

1) N2 + 3H2 --> 2NH3

2) NH3 + H+ --> NH4+

3) NH4+ + O2 --> NO2- + 4H+ + 2e-

4) NO2- + H2O --> NO3- + 2H+ + 2e-

5) 2NO3- + 10e- + 12H+ --> N2 + 6H2O

6) N2 + O2 --> 2NO

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Chemical production- cost and factors

% Atom economy = mass of desired product / total mass of all products x 100

% yield = actual product yield / theoretical yeild x 100

COSTS INVOLVED IN CHEMICAL PRODUCTION

  • Raw materials
  • Fuel/Energy
  • Overheads/Fixed costs
  • Disposal costs

Risks involved:

  • Some chemicals are highly flammable so carry the risk of explosions- must be stored and handled correctly.
  • Some chemicals are toxic to humans- must be stored and handled correctly.
  • Some chemicals can damage the environment.
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Chemicals & food production

The chemical industry can help with food production-

1) Fertilising the soil- this provides the crops with nutrients which improves plant growth and crop yield. 

However, rain can wash them into rivers which can cause excessive algae growth which can deplete the water of oxygen, killing off some species.

2) Acid neutralisation- adding chemicals into the soil can neutralise pH of the soil, leading to better plant growth overall.

3) Killing pests- pesticides can kill insects, weeds or moulds which all decrease crop yield and quality, so with them killed, yield and quality increases.

However, they can kill some beneficial organisms, and can be washed into water supplies which may be used for drinking water.

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