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Find out how changing the concentration of Sodium Thiosulphate in a sodium thiosulphate and hydrochloric acid solution effects the reaction rate.

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Introduction

GCSE Chemistry Coursework Aim: to find out how changing the concentration of Sodium Thiosulphate in a sodium thiosulphate and hydrochloric acid solution effects the reaction rate. Planning the experiment. Apparatus: Conical flask Paper with a cross on 35ml of Hydrochloric Acid 245ml of Sodium Thiosulphate 2 Measuring cylinders 180ml of tap water Stopclock Prediction: I predict that the more sodium thiosulphate in the solution, the faster reaction rate will be. This is because the solution must be concentrated so that bonds can be broken quicker. The more collisions in a given time, the faster the reaction will be. The reactants must hit each other hard to break bonds so this is why the solution must be very concentrated. Not all the collisions result in bonds breaking but the higher the concentration then the more collisions there will be and so there will be a higher chance of more collisions happening. Planned method: We had done preliminary work which I have included the results from in the evaluation section. In this experiment the variable is going to be sodium thiosulphate. I am going to start off with 65cm3 of sodium thiosulphate, 5 cm3 of hydrochloric acid and no water in a conical flask. When I add the acid to the flask, I will start the stopclock and put the flask on top of the piece of paper with a cross on it. ...read more.

Middle

1 Time(s) 2 Reaction rate 1 2 AV. 65 0 5 37.1 18:94 25:42 0.05 0.04 0.045 55 5 5 36.7 29:56 27:38 0.034 0.037 0.0355 45 15 5 30 33:10 44:79 0.030 0.022 0.026 35 25 5 23.3 53:43 54:35 0.019 0.018 0.0185 25 35 5 16.7 67:42 69:28 0.015 0.014 0.0145 15 45 5 10 142:51 122:63 0.007 0.0082 0.0076 5 55 5 3.3 767:83 612:68 0.001 0.0016 0.0013 Evaluation: This experiment was overall a success. There are a couple of possible anomalous results-the last two results I gathered I think are anomalous because they have a much slower reaction rate than the rest of the results and this shows on the graph. They are it is only slightly different to the pattern of the rest of the results, but enough for me to tell that they are anomalous. These results could be anomalous because of many reasons. It could be because slightly less of HCl or too much of sodium thiosulphate was added. When I repeated the experiment the second the first result where sodium thiosulphate was 65 and water was 0, the different between the first and second results was about 7 seconds which is a big gap so shows that it was an anomalous result. In the experiment we used burettes to measure the amount of sodium thiosulphate and water that was added to the solution, this is a more accurate method than using a measuring cylinder or pipette. ...read more.

Conclusion

Rate 50 0 32.7 32 0.028 40 10 41.54 32 0.024 30 20 45.48 24 0.022 20 30 65.12 16 0.015 10 40 74.34 8 0.013 These results show the same pattern as the set of results I obtained for my experiment and are further evidence towards my conclusion. Conclusion: After carrying out my experiment I can conclude that as the concentration of the solution increases, the reaction rate also increases, which means that they are directly proportional. The reaction rate is found by 1/time. The higher the concentration of the solution the closer the ions are. When the ions are closer they will collide more often and there will be a greater chance of bonds breaking. The more bonds that are broken in a shorter period of time, the faster the reaction rate will be. If you were to keep the concentration of Sodium Thiosulphate constant and alter the concentration of HCL, the reaction rate would be proportional to the concentration of the acid. When Sodium Thiosulphate and Hydrochloric acid react they form a precipitate of sulphur, a liquid form of sodium chloride and a sulphur dioxide gas. The gas given off is what gives it such a strong smell. This is the word equation for the reaction: Hydrochloric + Sodium ==> Sodium + Sulphur + Water Acid Thiosulphate Chloride Dioxide The symbolic equation for the experiment is: Na S 0 +2HCl ==> S+ 2NaCl + SO ...read more.

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