Investigate how the concentration of hydrochloric acid affects the rate of reaction between calcium carbonate and hydrochloric acid.

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GCSE Chemistry Coursework                Autumn Term 2003

My aim is to investigate how the concentration of hydrochloric acid affects the rate of reaction between calcium carbonate and hydrochloric acid.

The word and chemical equation which I have constructed for the experiment is:

Calcium    +  hydrochloric                    calcium  +   water   +   carbon

Carbonate            acid                             chloride                          dioxide.

  CaCo3       +     2HCL                            CaCl2     +    H2 O   +     CO2

               Reactant                                                      Product

I chose this reaction because it is easy to control as the production of carbon dioxide being produced can be monitored with ease. Additionally the amount of carbon dioxide given out can me measured accurately and fairly quickly.

From this equation, it is evident to us that hydrochloric acid has a large effect on the reaction. The calcium displaces the hydrogen from the hydrochloric acid which results in calcium chloride (marble) in being formed

I chose concentration as the variable because of its ease in changing in comparison to the other variables – temperature, surface area, concentration and catalyst. I did not choose the variable to be temperature because it is difficult to maintain and requires precise measurements. The surface area of the marble chips would too be too difficult to measure. Additionally catalysts was not the variable I chose, because this would only give me two results – whether the rate of reaction is faster with the catalyst or whether it is faster without the catalyst. I chose not to keep the concentration constant because it is easy to change and in comparison to these three other variables I think that it will be the quickest and most accurate variable. So temperature and surface area will be kept constant, no catalyst will be used and the concentration of hydrochloric acid will be the variable.

I could have investigated the effect of concentration on the reaction in several different ways as shown overleaf:

  • By observing or measuring how much of a product is used up, in this case how much calcium carbonate is dissolved in the hydrochloric acid.
  • By measuring the volume of carbon dioxide gas given off.
  • By counting the amount of bubbles given off.
  • By timing the reaction until a certain volume of carbon dioxide is produced.
  • By measuring the amount of carbon dioxide gas produced every 10 seconds.

I chose to measure the volume of carbon dioxide gas given off and by measuring the amount of carbon dioxide gas produced every 10 seconds for the main experiment because it was the two methods that are likely to give me the most accurate results. Additionally for the preliminary experiment I timed the reaction until 50 cm3 of carbon dioxide gad was produced, because I found this to be a fairly quick method but yet accurate, although not as accurate as the methods I used for the main experiment.

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In the preliminary experiment I will investigate the suitable conditions for this experiment – the volume of hydrochloric acid to use and the surface area of marble chips.

For this experiment I predict that the higher the concentration of hydrochloric acid, the faster the rate of reaction will be. I predict that the reaction will occur as shown below:

Calcium    +  hydrochloric                    calcium  +  water +  carbon

Carbonate   ...

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