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Introduction

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. ...read more.

Middle

As mentioned before, the surface area of a reactant affects the rate of the reaction therefore the same number of similarly sized chips will be used for each test in order to keep this the same. Also, the clock will be stopped at a certain volume of gas instead of reading the gas at a certain time. This is done so that it is possible to just look at the amount of gas, instead of having to check the volume when the stopwatch reaches a specific time, as it may have changed making it less accurate. Results:- A Table To Show How the concentration of hydrochloric acid affects the amount of carbon dioxide given off by marble chips while reacting Rate of reaction (ml/s) 1.27 0.94 0.45 0.25 0.0 Average (s) 15.8 21.3 44.8 80.4 0.0 Ex 4 (s) 16.1 20.9 42.1 95.4 0.0 Ex 3 (s) 12.3 22.5 54.8 78.4 0.0 Ex 2 (s) 15.4 20.4 44.1 79.6 0.0 Ex 1 (s) 15.9 26.5 48.2 83.2 0.0 Mass (g) 3 3 3 3 3 Concentration of acid (g/l) 72.0 54.0 36.0 18.0 0.0 Volume of water (ml) 0 5 10 15 20 Volume of acid (ml) 20 15 10 5 0 Volume of gas (cm3) 20 20 20 20 20 Analysis:- These results obtained from the experiment show that, like I predicted in my hypothesis, the reaction between the hydrochloric acid and the marble chips speeds up as the concentration of the acid increases. ...read more.

Conclusion

Another way to make the test more accurate, and one of the reasons that all the results were not concordant, could be to grind up the marble chips in order to give them all the same surface area while keeping the same mass. The same number and total weight of the chips was kept the same throughout the test, but it was too difficult to ensure that all chips were of the same surface area, which could have altered the speed of the reaction. Grinding the chips up into a powder would guarantee that the same surface area is used for each test, which would help to prove that it is the change in concentration that causes the changes in the rate of reaction, not other unintended variables. The experiment could be repeated with a larger number of concentrations at smaller intervals, maybe decreasing by two ml per test from 100ml of acid and no water down to no acid and 100ml of water. It could also be repeated with different masses of chips and volumes of carbon dioxide, such as seeing how long it takes for a reaction between 75ml of hydrochloric acid and 15ml of water, and 7g of marble chips to produce 50cm3 of carbon dioxide. Should these steps be taken then the experiment would provide better evidence to support the fact that the rate of reaction increases as the concentration of the acid increases. 1 Matthew Gerrett 11PR ...read more.

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