NPK fertilisers

• NPK fertilisers provide plants with the essential elements for growth
• formulated fertilisers are better as they are more widely available, easier to use, don't smell and have enough nutrients.
• three main elements in fertilisers are nitrogen, phosphorus and potassium. If plant don't get enough, their growth and life processes are affected. elements may be missing in soil if used up by previous crop
• fertilisers replace the missing elements or provide more. increase crop yield. nitrogen makes plants grow faster- increasing productivity.
• NPK contain salts of nitrogen, phosphorus and potassium in the right percentages of the elements.
• ammonia can be reacted with oxygen and water in a series of reaction to make nitric acid.
• you can also react ammonia with acids to get ammonium salts
• ammonia and nitric acid react together to produce ammonium nitrate - a good compound to use in a fertiliser because it has nitrogen from two sources
• ammonia + nitric acid -> ammonium nitrate
• in industry, the reaction is carried out in giant vats, high concentrations, very exothermic reaction. heat released is used as evaporate water from the mixture to make a very concentrated ammonium nitrate product
• in the lab the reaction is carried out on s smaller scale by titration and crystallisation. reactants at lower concentration than in industry less heat is produced so safer. after titration, mixture needs to be crystallised to give pure ammonium nitrate crystal.
• crystallisation not used in industry as it is slow
• nitrogen is for healthy foliage - healthy leaves for photosynthesis
• the phosphorus gives strong roots and a thick stem, which helps the plant to absorb water and minerals
• the potassium is for healthy growth
• ammonium salts are a source of nitrogen
• ammonia is reacted with oxygen and a platinum catalyst to produce nitric oxide. this then reacts with oxygen and water to produce nitric acid. this then reacts with ammonium to produce ammonium nitrate
• potassium salts are soluble so can be directly used as fertilisers
• phosphate in rocks is insoluble, so we react it with acids to produce soluble phosphates
• phosphorus compounds in rocks reacting with acids creates nitric acid, sulfuric acid, phosphoric acid