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To find how changing the concentration changes the rate of reaction."

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David Robinson... Chemistry Science 1 Miss Armitstead Year 11 Boys. Preliminary Research... Before I conducted my research I tried to do my experiment using only 5cm2 of both the chemicals but found that this was to little and I found it to hard to decipher weather or not the chemical reaction had finish. So to help my experiment be more accurate I used 50cm2. Before I carry out the real experiment I am going to do a smaller one to see what molar acid I will use for the final experiment. I am using 100% sodium thiosulphate and a variety of molars. 100% thio 1m 2m 3m 4m Time(secs) 37.61 29.39 14.87 5.11 I am going to use one molar acid as I will be able to produce more accurate results, this is because it takes longer for the reaction to take place, and so this will make it easier to measure precisely. Secondary Research... The Graph above is a graph to show the relationship between Rate of Reaction and Concentration. ...read more.


Method. To start I will need to set up all my equipment as you can see from my diagram above. (Under the flask you should place you should place your cross.) I will start by measuring 50cm* of Hydrochloric acid and pour this into the flask. I will then take 50cm* of sodium Thiosulphate. As soon as you pour this into the flask you must start timing. You should only stop timing when you can no longer see the cross I will repeat each different concentration five times. As I have realised the temperature is a variable I will take the temperature throughout this experiment. I will do this to ensure it stays at a constant temperature, as it will not effect my results. Safety. To make my experiment safe I will wear safety and clean up any spills immediately. Results. % Concentration Time (secs) 1 2 3 4 5 avg. Reac. Rate 100% 28.09 29.41 28.54 25.63 30.06 28.35 0.035 80% 37.03 30.18 32.25 33.27 34.5 33.44 0.029 60% 38.94 40.38 41.63 45.13 42.06 41.63 0.024 40% 60.61 59.92 62.47 60.31 102.69 69.2 0.014 20% 135.28 ...read more.


2.7% + 7.4% + 10.9% + 9.6% + 1.6% = 32.2% = 6.44% 5 Conclusion. I have found out that my quantified prediction was correct, as when the concentration doubled so does the rate of reaction. I have proved this by my percentage error only being 6.44% This is because when the concentration doubles the amount of particles have also doubled and so the amount of time taken for each particle to collide and react has shortened or halved and so the time taken has also done the same. Improvements. If I did the experiment again I could improve it by reacting the two chemicals more times. Currently I have only reacted each concentration five times if I did each one ten times the accuracy would be better. I could also change the percentage of Sodium Thiosulphate by 10% instead of 20%. I could change the concentration of the acid and see what happens. The final alteration I could make would be to test for temperature instead of concentration. ...read more.

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