fertilisers

• there are 3 key elements which provide the nutrients required for plant growth: nitrogen, phosphorus and potassium
• sometimes the soil does not contain enough of these important elements to fertilisers are used
• synthetic fertilisers are used in place of natural fertilisers due to the high demands of food production
• ammonia is a clear, colourless gas which dissolves in water to produce an alkaline solution
• ammonia is a very strong gas which can affect your breathing
• ammonia is a very soluble gas
• ammonia solution is a weak alkali with mostly NH3 molecules with a very few OH- ions
• ammonia solution + acid ⇌ ammonium salt + water
• ammonia can be reacted with nitric acid to to produce soluble, nitrogen containing salts that can be used as fertilisers
• ammomium chloride gas

  A) cotton wool soaked in ammomia

  B) white ring of ammonium chloride forms

  C) cotton wool soaked in hydrochloric acid

  
• ammonium chloride + sodium hydroxide ⇌ ammonia + water + sodium chloride
• because the reaction is reversible, the ammonium salt can be decomposed back into ammonia gas if heated with a strong alkali like sodium hydroxide
• a platinum catalyst is used to increase surface area in the ostwald process
• N2(g) + 3H2(g) ⇌ 2NH3(g)
• a high temperature is used to speed up the rate of reaction even though it gives a low yield
• in the haber process the mixture is heated to about 450 degrees
• an iron catalyst is used to increase the rate of reaction in the haber process
• the pressure in the haber process is around 200 atmospheres
• the most cost effective process gives about a 15% yield
• unreacted hydrogen and nitrogen are recycled to save valuable energy
• nitrogen oxides in the atmosphere can contribute to acid rain
• NH3(g) + 2O2(g) → 4HNO3(aq) + H2O(l)
• the ostwald process used ammonia, oxygen and water to produce nitric acid