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How Does Temperature Affect the Rate of Reaction Between Hydrochloric Acid and Sodium Thiosulphate

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Investigating How Temperature Affects The Rate Of Reaction Between Hydrochloric Acid and Sodium Thiosulphate Aim: To investigate how temperature affects rate of reaction between hydrochloric acid and sodium thiosulphate. Background Info When sodium thiosulphate reacts with hydrochloric acid (or any acid) it forms a yellow precipitate. This is sulphur, as shown in this equation: Na2S2O3(aq) + 2HCl(aq) ---> 2NaCl(aq) + SO2(g) + H2O(l) + S(s) Sodium thiosulphate + hydrochloric acid --> sodium chloride + sulphur dioxide + water + sulphur The sulphur precipitate, when the beaker is placed over a cross, will obscure the cross and by timing how long this takes we can time the rate of reaction. It should work out that the higher the temperature, the faster the rate of reaction. This is because higher temperatures give particles more energy so they move around more, and in turn this means that there are more collisions per second. When particles collide, they react with each other so more collisions means a faster reaction. This is called collision theory. Activation energy is the minimum energy needed to start a reaction. If particles collide with less than the activation energy, no reaction will occur. It can be thought of as a barrier to the reaction. Various things increase energy and break this barrier so that reaction can take place. Shaking the mixture (in a conical flask) is one of time, because it makes particles collide more frequently and more violently. Higher temperature is another, because it gives particles more energy and they move more, so collide more frequently. ...read more.


Unfortunately, because the unheated sodium thiosulphate which is added afterwards will cool it down and it will cool down while reacting, it will be very hard to get the exact right temperature. I predict that the actual temperature will be about three degrees lower than what we aim for. One more thing that could decrease the reliability of our results is if we use different apparatus for the different temperatures and repeats, for instance a more powerful bunsen burner or a slightly faulty thermometer could affect our results. For this reason, we will make sure we use the same apparatus each time. Results The graphs I plotted support my prediction to an extent and support the background information. However, my prediction was not accurate because I predicted that with every 10�C increase, the time taken to obscure the cross would decrease by 4 seconds. In reality, the rate of reaction increased by less and less with each 10�C increase. For instance when we increased the temperature from 20�C to 30�C, the time taken to react decreased by 30.31s, whilst when the temperature was increased from 30�C to 40�C, the time decreased by 7.03s, nowhere near as dramatic an increase in rate as the 20�C to 30�C jump. By my original prediction, in both the 20�C to 30�C increase and the 30�C to 40�C increase, the time taken to react would have decreased by 4s, consistently. I drew a graph of time plotted against temperature, and the results formed a steep downwards curve, presenting visually the fact that each 10�C increase does not decrease the time taken by the same amount. ...read more.


or not, and as we shook it for five seconds each time, the cross could have been obscured whilst we were shaking the beaker so our times might be slightly off. There is also the danger of us shaking more vigorously for one temperature than another (for whatever reason), which would make the results for which the beaker was shaken harder have a faster reaction time than the others. To combat this, we could have of course just waited for the reactants to obscure the cross without touching the beaker, but I believe this would have taken too long, considering the amount of time available to us. I think stirring would be the best option as this allows you to see whether the cross has been obscured, but would still speed up the reaction enough to be practical. If I was to look into this area further, I could stay with hydrochloric acid and sodium thiosulphate, and try a different range of temperatures. For instance, it would be interesting to see whether differences of about 2�C, for instance from 30�C to 40�C increasing in 2�C jumps, would give as strong results - how much rate of reaction is affected by small fluctuations in temperature. I could also try the experiment whilst both reactants were on the heat. This would get rid of the problem of the unheated sodium thiosulphate and the surrounding air cooling down the hydrochloric acid, but it would also mean adjusting the bunsen burner constantly to keep them reacting at the needed temperature. This could be difficult to manoeuvre, and therefore unreliable. ...read more.

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