An Experiment To Investigate The Rate Of Reaction Between Marble Chips And Hydrochloric Acid.

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An Experiment To Investigate The Rate Of Reaction Between Marble Chips And Hydrochloric Acid

        The aim of this experiment is to find out if the concentration of hydrochloric acid affects the amount of carbon dioxide given off by marble chips while reacting with the acid.

Apparatus:-

Test tube 

Stopper connected to rubber tube

2 measuring cylinders

Basin of water 

Stopwatch

20 ml solution of acid and water

3g of marble chips

Scales

The experiment will begin by setting up the above apparatus. 20 millilitres of 2 molar hydrochloric acid will then be measured out using a measuring cylinder and put into a test tube, and 3 grams of calcium carbonate, in the form of 5 marble chips, will be weighed out using some electronic scales. The upturned measuring cylinder in the basin of water will be put in so that all the air inside is replaced by water, and will have to be kept upright in order to read to volumes accurately. The marble chips will then be added to the acid in the test tube, and the stopwatch will be started as the stopper is put in.

Being a base, marble, or CaCO3, reacts with acid to produce a salt (calcium chloride), water and carbon dioxide. The carbon dioxide generated by the reaction will travel through the airtight tube and will displace the water in the measuring cylinder, which will allow the volume of gas to be measured. The stopwatch will be stopped when the amount of carbon dioxide collected reaches 20cm3, and the time will be recorded, along with enough tests to obtain three concordant results. This will be done in order to make it a fair test and make sure that any anomalies can be identified. Since the experiment is exploring the rate of reaction between marble chips and different concentrations of hydrochloric acid, the whole experiment will be repeated using 15ml, 10ml, 5ml and 0ml of 2 molar HCl, and adding the appropriate amount of water to bring the total volume of the solution up to 20ml.

A preliminary experiment showed that the reaction between 5 marble chips weighing 3g in total and 20ml of acid produced 20cm3 in 18.50 seconds. When the same amount of chips reacted with 5ml of acid and 15ml of water, it took 85.56s, which showed a large enough difference so that each concentration could be easily distinguished from one another. The following table and graph show the results ascertained from the preliminary experiment.

        Reactions cannot occur by simply putting two substances together. The substances must be reactant with each other, the particles must collide with each other, and they must collide with enough energy to break the bonds that keep the particles together. This amount of energy is called the activation energy, or the Ea. There are two ways in which to increase the rate of reaction: giving the particles more energy, which gives more particles the activation energy, and also by increasing the frequency of collisions. This can be done in a few ways. Heating up a reaction gives the particles more energy, making more particles collide with the activation energy. Another way to speed up a reaction is to increase the concentration of reactants, which means that there are more particles to collide with each other making collisions occur more frequently. Two other ways to speed up a reaction are using a catalyst to lower the activation energy needed for the particles to react, and grinding up a solid in order to increase the surface area and allowing more particles to react.

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        However, this experiment is to find out if the concentration of hydrochloric acid affects the reaction. This means that all the other ways to speed up a reaction will not be used in order to prove that it is the concentration that causes any changes. Since the concentration of the acid will be the only variable, the mass of the marble chips will be kept at 3g, there will only be 5 similarly sized chips per reaction in order to keep the surface area about the same, the volume of the acid solution will always be 20ml and the temperature ...

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