Chemistry Controlled Assesment Research

Chemistry Controlled Assessment Research – Descaling coffee machines
Q1) The advantages and disadvantages of these commonly used de-scalers
Ethanoic Acid (Acetic Acid)
Citric Acid
Sulfamic Acid
Ethanoic Acid
Advantages:
Ethanoic acid is non-toxic and is a weak acid [4], meaning it will not do any damage to most surfaces as it does not corrode or bind to other metals, therefore can be easily removed through washing or rinsing it [2].
Disadvantages:
Ethanoic Acid is the slowest de-scaler of the three acids, and is therefore the least effective. It also may cause an unpleasant smell, and can have a negative effect on the taste of coffee [6] meaning one would need to spend longer time rinsing and cleaning the machine thoroughly to ensure that the taste of the coffee is not affected.
Citric Acid
Advantages:
Citric acid leaves behind zero toxic residues and has just enough acidic concentration to descale without etching or damaging household surfaces in any way and there are no volatile compounds or products that harm the environment.
Disadvantages:
Because citric acid is a weak acid, it won't remove heavy build-up of scale very quickly. It is also a powder hence it must be dissolved for use. It also works best with hot water meaning there will be higher energy consumption. Even when used with hot water, citric acid is not as effective at descaling as Sulfamic acid.
Sulfamic Acid
Advantages:
Sulfamic acid is the fastest de-scaler - It dissociates into hydroxonium ions more readily in aqueous solution than the others, therefore giving a greater concentration of atoms that are able to react with the calcium in lime scale. It is safe to use because it does not produce chlorine gas [5], which can be toxic. Sulfamic acid also has a low volatility.
Disadvantages:
Sulfamic Acid can be an irritant to eyes or skin and is the most expensive of the de-scalers.

Limescale is mainly composed of calcium carbonate, CaCO3. All acids react with carbonate compounds to...