Testing Acids To Use For De-Scaling Coffee Machines

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Controlled Assessment De-scaling Kettles

Research and Collecting Secondary Data

De-scalers are substances that help remove limescale of many household products. They are found in many homes. Limescale is found in products such as washing machine, kettles and pipes. The most common de-scalers are ethanoic acid, citric acid and sulfamic acid. These react with calcium carbonate which is limescale. This is a neutralisation reaction.

Advantages and Disadvantages of Ethanoic Acid, Citric Acid and Sulfamic Acid

Advantages of ethanoic acid:

Ethanoic is an acid that is non-toxic and weak. This means that it will not do any harm to most surfaces because dies not corrode or attach to other metals, and so are often simply removed through washing or rinsing it.

Disadvantages of ethanoic acid:

The problem with ethanoic acid is that it is the slowest de-scaler out of the three acids, and is consequently the least effective. It additionally might cause unpleasant smells, and may have a negative result on the taste of coffee, which means one would want to spend longer time cleaning the machine completely to make sure that the taste of the coffee isn’t affected.

Advantages of citric acid:

Like ethanoic acid, citric acid is not toxic and doesn’t leave any toxic deposit. It just has enough acidity to descale without leaving marks or damaging household surfaces. There are also no unstable compounds or products that harm the environment.

Disadvantages of citric acid:

Citric acid is a weak acid. This means that it won’t remove a lot of scale very quickly. Also it is a powder. This means that it needs to be dissolved in a liquid before it can be used. It also works better if you use boiling water as there is more energy to be used for the reaction. However, it is still not as effective sulfamic acid

Advantages of sulfamic acid:

This acid is the fastest de-scaler. It separates into hydroxonium ions more readily in watery liquids than the other acids. Therefore there are more atoms to react with the calcium in limescale. This acid does not produce any harmful and toxic gases such as chlorine.

Disadvantages of sulfamic acid:

Sulfamic acid is very irritating to some people’s eyes and skin and is also the most expensive.


How do de-scalers remove limescale??

Limescale is formed when hard water is boiled above 60oC or more. Hard water is when water is boiled in the presence of calcium. When this is boiled it reacts with carbon dioxide leaving behind the limescale (calcium carbonate). De-scalers react with the calcium carbonate in a neutralisation reaction.

Sulfamic Acid + Calcium Carbonate ---> Calcium Sulfamate + Carbon Dioxide + Water

2H3NSO3+ CaCO3 ---> Ca (S03NH2)2 + CO2 + H2O

Citric Acid + Calcium Carbonate = Calcium Citrate + Carbon dioxide + Water.

2C6H8O7 + 3CaCO3 ---> Ca3 (C6H5O7)2 + 3CO2 + 3H2O

Ethanoic Acid + Calcium Carbonate --> Calcium Ethanoate + Carbon Dioxide + Water

2CH3COOH + CaCO3 ---> Ca (CH3CO2)2 + CO2 + H2O

What is Collision Theory?

As the temperature increases, the kinetic energy in the atoms increases and they move faster. The faster the movement of the atoms the more chance of a collision occurring, thus the rate of collisions increases. Therefore, the more collisions there are the faster the reaction. As the atoms have more energy when they collide, the more chance for a successful. Increasing concentration increases the number of particles in the same volume as the particles are more crowded together. The more crowded the particles the more chance of them colliding together.

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PH in Descaling

PH is used to measure the acidity or alkalinity a substance is, the scale ranging from 1-14. If the substance is 7 on the scale, it is neutral. If it is less than 7 it is acidic, but if it higher than 7 it is an alkaline. The lower the number, the stronger the acid is. The higher the number the more alkaline it is. If a substance is acidic, you can use an alkaline to make it neutral, and vice-versa. This is called neutralisation. The experiment we conducted was a neutralisation reaction test. We had used ...

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