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Controlled Assessment - Fertlilisers Research

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Introduction

Fertilisers Fertilisers are made from ammonia and are used in modern farming as they increase crop yield. The three main fertilisers made from ammonia include, ammonium nitrate, ammonium sulphate and urea. How are they manufactured? Fertilisers are made by the reaction of an acid and an alkali. The preparation of a fertiliser in a lab involves the following equipment: a measuring cylinder to measure the volume of a particular acid, a burette to add an alkali to the acid to try and make the solution neutral and a filter funnel to remove the solid crystals of fertiliser from the solution. The pH (power of hydrogen) value of the solution can be measured by taking samples while using universal indicator. In our examples; ammonia is reacted with nitric acid to make ammonium nitrate and ammonia is reacted with sulphuric acid to make ammonium sulphate. [2] NH3 + HNO3 � NH4NO3 Ammonia + Nitric Acid � Ammonium Nitrate NH3 + H2SO4 � (NH4)2SO4 Ammonia + Sulphuric Acid � Ammonium Sulphate When these fertilisers are manufactured in a factory the ammonia and the acid are pumped into a mixing vessel, where the solution is neutralised. ...read more.

Middle

- Urea usage involves little or no fire or explosion hazard. - Urea manufacture releases few pollutants to the environment. - Urea has the highest nitrogen content, at 46%. This percentage is much higher than other nitrogenous fertilizers available in the market. - The cost of production of urea is low because carbon dioxide, required for its manufacture, can be easily obtained from crude naphtha. Disadvantages of urea: - Urea is very soluble in water, and hygroscopic water (hygroscopic water creates a thin layer surrounding individual soil particles, which makes water unavailable to plants), and it therefore requires better packaging quality. - It is not as stable as other solid nitrogenous fertilizers. It decomposes even at room temperatures, particularly in a humid atmosphere. It releases ammonia and carbon dioxide into the air. - If urea contains impurities more than 2%, it cannot be used as a fertilizer, since the impurities are toxic to certain crops, particularly citrus. ...read more.

Conclusion

[6] Specific heat capacity for the acids: Nitric acid = 1.74 J/g �C Sulphuric acid = 1.42 J/g �C How an acid reacts with an alkali in a neutralisation reaction: An acid and an alkali react to produce salt and water. This is usually an exothermic process. In general, acid and alkali reactions can be simplified to: OH- + H+ � H2O Acids are generally pure substances that contain hydrogen ions (H+) or cause them to be produced in solutions. Sulphuric acid is an example of this (H2SO4). In water, it breaks apart into ions: H2SO4 � H+ + HSO4 - In general, alkalis are defined as substances that contain the hydroxide ion (OH-) or produce it in solution. One example would be sodium hydroxide (NaOH). To produce hydroxide ions in water, the alkali breaks apart into ions: NaOH � Na+ + OH- Therefore, the ions from an acid and an alkali react to cancel each other out and produce a neutral solution. The resultant pH value will generally be pH 7 and this is shown as a green colour on universal indicator paper. ...read more.

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Here's what a teacher thought of this essay

4 star(s)

A 4 star essay with good detailed scientific knowledge of a fertiliser. Some more general information would improve the introduction but there is a good balance of advantages and disadvantages next. Good accurate detail to describe neutralisation.

Marked by teacher Patricia McHugh 08/04/2013

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