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Investigating a Factor affecting the rate of reaction between Sodium Thiosulphate and dilute Hydrochloric acid

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Investigating a Factor affecting the rate of reaction between Sodium Thiosulphate and dilute Hydrochloric acid Planning We have been asked to investigate the rates of a reaction and the effect different changes have on it. The rate of a reaction can be described as the rate of loss of a reactant or the rate of formation of a product during a chemical reaction. This rate is calculated by dividing 1 by the time taken for the reaction to occur. The reaction I have been asked to investigate is: Sodium Thiosulphate + Hydrochloric Acid ? Sodium Chloride + Water + Sulphur Dioxide + Sulphur Na2 S3 O2 (aq) + 2HCl (aq) ? 2NaCl (aq) + H2O (l) + SO2 (aq) + S(s) The dilute Hydrochloric acid reacts with the Sodium Thiosulphate solution to give a precipitate of sulphur. Both liquids are clear and colourless before they react. The appearance of the insoluble sulphur during the reaction makes the mixture cloudy. The cloudiness increases as the reaction is allowed to proceed. According to the collision theory of reacting particles, there are five factors that affect the rate of a reaction: * Concentration (of solution) * Temperature * Pressure (in gases) ...read more.


I can do this by either swirling it a set number of times or not swirling it at all. I have decided to do the latter of the two, which will be easier and because if I swirled the flask a set number of times, there would be a possibility of swirling it with different forces. The stopwatch I used measured only to seconds and not any decimal places, which means that the results were not accurate enough. For my actual experiment I will use a stopwatch which measures to two decimal places. Volume of Sodium Thiosulphate (ml) Volume of Water (ml) Concentration of Solution (mol/dm3) Time taken for reaction to occur (s) Average time (s) Rate of Reaction 1 2 50 0 0.15 31.31 33.57 32.44 0.031 40 10 0.12 38.84 40.59 39.72 0.025 30 20 0.09 57.05 57.71 57.38 0.017 20 30 0.06 78.40 81.56 79.98 0.013 10 40 0.03 164.61 148.81 156.71 0.006 0 50 0.00 No reaction No reaction No reaction No reaction Results To improve the reliability of my results, we used the same person to look at the cross through the solution and decide when they could not see the cross anymore. If we hadn't done this the experiment would not have been a fair test because my partner and I have very different eye sight. ...read more.


If I did the experiment again I would repeat the experiment one more time to improve the reliability. I don't think the way we measured when the experiment had stopped was very accurate because it was very hard to tell when the cross was impossible to see anymore. So, if I was to do the experiment again I would choose a reaction which results in bubbling, so that it would be easier to tell when the experiment has come to a halt. My results are reliable as well because when I took the repeats of each concentration, they did not vary much. All of my results are consistent with each other and no results were so different that they should have been ignored. However, I could have repeated the experiment again, but I doubt that they would have changed the average very much unless they were particularly anomalous. To extend my enquiry I could investigate the rate of a different reaction using solid and a liquid instead of two liquids. This would also give me a chance to change the surface area of the solid reactant, which I could not do in this experiment. I could then look at the graphs that my results will have given me to see if they show the same trends as in this experiment. ...read more.

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