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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. ...read more.


Next insert the syringe to the end of the delivery tube 11. When the syringe is in place , start the stopwatch 12. For every five seconds for the next thirty seconds, measure the amount of carbon dioxide that is released and record the information in a table Minimising Errors Minimising errors is reducing the amount of potential errors and mistakes during an experiment. By doing this, we can make the results of the experiment more accurate. First, we are using a pipette to get accurate volumes of water and the standard solution. This is so that all the experiments are fair. The amount of citric acid was also measured using the pipette. The amount of citric acid and calcium carbonate were kept the same. This is, again, because we wanted to keep it a fair test. We also made sure to close the conical straight away with the rubber bung. This would prevent any carbon dioxide from escaping after the reaction had started to happen. We kept the syringe perfectly sideways and not tilted. This was so that gravity did not move the syringe around, changing the values. We made sure that the timings were recorded correctly and we used a scale with two decimal places. This gave us an accurate measure of time and how much substance we were using. Risk assessment Hazardous substance/equipment Nature of the hazard Source of information Control measures Calcium carbonate Irritation of eyes, skin and respiratory systems, coughing Cleapss Student safety sheet Wear goggles and avoid touching eyes. Electricity Water spilling near or into electrical sockets. ...read more.


Secondly, citric acid does not pose many risks to the environment around it. This cannot be said for ethanoic acid, which is a vinegar. Vinegar is usually used to as flavouring: therefore it may have an effect on the taste of coffee which is being made by the coffee machine if it is not cleaned thoroughly. Another reason is that citric acid has lower pH than ethanoic acid. This is because citric acid is tribasic while ethanoic is monobasic, meaning citric acid has more free hydrogen ions. Having a lower pH means that it has a faster rate of reaction as it has a higher concentration, meaning that the numbers of particles which collide are higher. This reduces the time needed to get rid of lime scale. Sulfamic acid is more expensive than citric acid. Sulfamic acid is often preferred to citric acid because it works more quickly. Explain why sulfamic acid works more quickly. Use information from your research and your investigation. Use relevant scientific explanations in your answer. The first reason why sulfamic acid works faster is that it has a pH of 2 while citric acid has a pH of 2.2. Having a lower pH value means that it is more acidic, therefore a more powerful de-scalar. It also means that the molar mass of sulfamic acid is higher than citric acid. This means that there are more hydrogen ions in the solution, thus the rate of reaction will be higher as there are more free ions available to collide and cause a reaction. Sulfamic also has a low toxicity and low volatility making it safe to use. It also is soluble in water making it easy to apply. ...read more.

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