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Sodium thiosulphate and hydrochloric acid

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Introduction

Sodium thiosulphate and hydrochloric acid Investigation I am measuring the rate of reaction of sodium thiosulphate and hydrochloric acid. There are different variables I could use to see the change in the rate of reaction. These include temperature, concentration or catalysts. I am going to do two experiments, one changing the temperature and one changing the concentration of the sodium thiosulphate. Sodium Thiosulphate + Hydrochloric Acid Sulphur + Sulphur dioxide + sodium chloride Na2S2O3 (aq) + 2HCl (aq) S(s) + SO2 (g) + 2NaCl(aq) Equipment Sodium thiosulphate (Na2S2O3) of different concentrations Hydrochloric acid (HCl) Tile marked with a cross Measuring cylinder (x2) Beaker Bunsen Tripod Test tube (x2) Stopwatch Thermometer Cold water Experiment Firstly I will measure the right amount of sodium thiosulphate and hydrochloric acid into two separate test tubes. If it is needed, these will then be put into water and heated with a Bunsen burner and tripod until they are up to temperature, which will be measured with a thermometer in the water. They will then be put into the beaker. Firstly, the experiment will be done with the substances in cold water then at room temperature. ...read more.

Middle

This is because the molecules will collide more often and with greater energy and so will be more likely to react because their bonds break. Therefore I predict that in the experiment were the temperature is changed, the rate of reaction will go up as the temperature goes up. In the experiment where the concentration of the thiosulphate is to be varied, I expect also the rate of reaction to go up as the concentration goes up. If the concentration doubles, I would expect the rate of reaction to double and if the concentration is zero I would expect the rate of reaction to be zero. In the first half of the experiment everything will be kept the same except the temperature, which will range from 10oC to 60oC. The concentration of the sodium thiosulphate used throughout will be 30g/dm. In the other half to the experiment everything will be the same apart from the concentration of the sodium thiosulphate. The concentration will be no less than 15g/dm because any less than this would probably take too long. ...read more.

Conclusion

The reason there are two graphs for the first table is that one shows time taken for cross to disappear and the other shows rate of reaction. The third shows the time taken for the cross to disappear in the second experiment and the fourth shows the rate of reaction in the second experiment. Graph one and three show negative correlations while graph two and four show positive correlation. Evaluating evidence The way I used to do the experiments was good and produced good results but it could have been improved. The results are good, there are no odd results and itcame out as predicted. This could mean that the experiment was done perfectly. Although all the average times and rates of reaction all correlate, they are not all evenly spaced and therefore are probably not perfect. Improvements It would have been good to do more repeats. Three tests were managed each time but if one had been wrong this could have severely changed the average time and therefore rate of reaction. Conclusion I think this was a good experiment and was done as well and as accurately as I could have made it. The results support my predictions and they seem to be reliable. ...read more.

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