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Rates of reaction in a sodium thiosulphate and hydrochloric acid solution.

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Aim: - To investigate the effects of changes in concentration of sodium thiosulphate on the rate of its reaction with hydrochloric acid. The word equation of the reaction is: - Sodium Thiosulphate + Hydrochloric Acid ==> Sodium Chloride + Water + Sulphur Dioxide + Sulphur Na2S2O3 (aq) + 2HCl (aq) ==> 2NaCl (aq) + H2O (l) + SO2 (g) + S (s) Introduction: - I am going to be testing the effect that the concentration of sodium thiosulphate solution has on the rate of reaction when mixed with hydrochloric acid. When these two chemicals start out they are both clear liquids. As they react after being mixed together the solution gets cloudy. In order to measure the time taken to react I shall use a simple method. I shall draw a cross on a piece of white paper and put it under the conical flask containing the solution. When can no longer see the cross, I shall stop the stopwatch. I predict that the greater the concentration of thiosulphate solution the faster the reaction, and so the faster the solution will go cloudy. ...read more.


Once they are both in the conical flak I then stated the stopwatch. When the mixture has turned cloudy so that the letter X could no longer be seen the stopwatch was stopped and the time was recorded. The experiment is repeated with all the concentrations. The whole procedure is then repeated four times to ensure that I have a fair test and then I can calculate the averages then the rate of reaction. Safety: - A pair of goggles was worn during the experiment in order to protect the eyes from any possible splash that might be caused by the sulphur dioxide released. When handling beakers and measuring cylinders I used a pair of tongs. Care was taken to protect the table from acid I also tucked in any of my loss clothing to prevent it dipping in the acid. Fair Test: - In order for my findings to be valid the experiment must be a fair one. I will use the same standard each time for judging when the X has disappeared. I will make sure that the measuring cylinders for the HCl and thiosulphate will not be mixed up. ...read more.


I expected the line of the graph to be a lot more curved. Adding also that when you look at the graph for the rates of reaction you can quite easily see that it shows a strong negative correlation. The line of this graph goes in a straight line like I expected it to. In my prediction I predicted that, as the concentration of the hydrochloric acid increases the rate of reaction will also increase. So as the concentration gets weaker the time taken for the solution to go cloudy will be of a longer period of time. I think now that I have completed the experiment I can quite easily state that the prediction that I made was very good and accurate. I think that if we done this investigation in the summer we might have had different results because in the summer the temperature in the room is a lot hotter than in the winter and that might have had an effect on the overall readings. Also if we had a stronger solution perhaps the results might have been effected.; 2 1 James Gillett SC1 Chemistry ...read more.

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