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  • Level: GCSE
  • Subject: Science
  • Essay length: 2214 words

Experiment to investigate the rates of reaction between sodium thiosulphate solution and dilute hydrochloric acid.

Extracts from this essay...

Introduction

Experiment to Investigate the Rates of Reaction between Sodium Thiosulphate Solution and Dilute Hydrochloric Acid I am going to be doing an experiment to study the rate of reaction between sodium thiosulphate solution and dilute hydrochloric acid. The chemical equation for this reaction is: Na2S2O3 (aq) + 2 HCl (aq) ? S (s) + SO2 (g) + 2 NaCl (aq) + H2O (l) During this chemical reaction there is a slow formation precipitate of solid sulphur. As a result, the solution in which the reaction is taking place gets gradually cloudier. The time the reaction takes to reach a certain point of cloudiness can be measured, by placing the flask over a white sheet of paper onto which a black cross is drawn. Eventually the solution will become so cloudy that you can no longer see the cross. In this way you can study the rate of reaction (how fast it goes under different conditions). Prediction: I predict that the higher the concentration of sodium thiosulphate solution, the quicker the rate of reaction will be to produce solid sulphur, which is the precipitate formed from the chemical reaction. So, the more dilute the sodium thiosulphate solution is, the slower the rate of reaction will be to produce the precipitate.

Middle

10. Once this has been repeated three times, the experiment will be done again, except that the amount of sodium thiosulphate solution used, will be decreased by 10ml, and the amount of dilute hydrochloric acid will remain the same. To keep the total volume the same, to keep it a fair experiment, 10ml of water will also be added, which will dilute the sodium thiosulphate solution to make it a weaker solution. 11. This will also be repeated three times, so that an average can be worked out. Once this has been completed, the experiment will continue, but the amount of sodium thiosulphate solution will be decreased by 10ml each time, and more water will be added each time to keep the total volume of the solution constant, and to lower the concentration of the sodium thiosulphate solution. The amount of dilute hydrochloric acid must be kept the same throughout the whole experiment, since we are testing for the difference in the rate of reaction, that sodium thiosulphate solution makes happen when tested at different concentration levels with dilute hydrochloric acid. 12. All together, there should be five slightly different experiments where the concentration of the sodium thiosulphate solution will vary by 10ml each time. All of these will be repeated three times to give averages and more reliable results.

Conclusion

E.g. If any water is left in the flask from washing it up, if a different flask can't be used then any of the excess water could dilute sodium thiosulphate solution more than it is supposed, therefore affecting the results. Further work, which could be done to give more evidence for rates of reaction, could be to test the effect of temperature on particles in a solution, since scientists believe that 6as we increase the temperature, we increase the rate of reaction. Further improvements, could be to re-do the experiment over again to check if the anomalous result resulted in any thing that went wrong during the first experiment, so to be as accurate as possible, this could be done to check it. 1 T. Lister and J. Renshaw Understanding Chemistry for Advanced Level (Cheltenham: Stanley Thornes (Publishers) Ltd, 1991), 373 2 L. Ryan Chemistry For You (Cheltenham: Stanley Thornes (Publishers) Ltd, 1996), 194 3 L. Ryan Chemistry For You (Cheltenham: Stanley Thornes (Publishers) Ltd, 1996), 195 4 T. Lister and J. Renshaw Understanding Chemistry for Advanced Level (Cheltenham: Stanley Thornes (Publishers) Ltd, 1991), 373 5 L. Ryan Chemistry For You (Cheltenham: Stanley Thornes (Publishers) Ltd, 1996), 197 6 L. Ryan Chemistry For You (Cheltenham: Stanley Thornes (Publishers) Ltd, 1996), 192 C: My Documents/ Kirsten Stone 11X/ Chem Exp. Rates of Reaction (Coursework) 1

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