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How Concentration Affects a Reaction.

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Chemistry Coursework How Concentration Affects a Reaction Aim: The aim of this experiment is to find out how concentration affects the rate of reaction between Hydrochloric Acid and Sodium Thiosulphate. Introduction: This experiment will be carried out by drawing a cross on a piece of paper and mixing hydrochloric acid and sodium thiosulphate together to see if the cross disappears. The concentration of hydrochloric acid would change every reaction to show that concentration effects a reaction. The time in which the cross took to disappear would be recorded as well as the temperature at the start and end of the reaction, the concentration of the hydrochloric acid and the amount of hydrochloric acid and sodium thiosulphate used. Preliminary Work: The problems that arose whilst doing the preliminary experiment was that the beakers and measuring cylinders were not cleaned out properly and some of the sodium thiosulphate turned cloudy were there was previously hydrochloric acid inside the beaker. The preliminary experiment showed that concentration effects the rate of reaction as well as the temperature does. Attempts Concentration (M) Amount of HCl/STs (ml�) ...read more.


Apparatus: * 2 Beakers * 2 Measuring Cylinders * Hydrochloric Acid (0.25M, 0.5M, 1M, 1.25M, 1.5M, 2M) * Sodium Thiosulphate * Conical Flask * Stand * Palm Top * Apron * Goggles * Thermometer Method: 1. Put on apron and goggles 2. Collect chosen amount of HCl and STs 3. Collect all equipment 4. Measure the correct amount of HCl and STs 5. Set up palm top and stand 6. Measure starting temperature 7. Mix together HCl and STs 8. Start the timing and when LUX decreased by 10% stop timing 9. Measure ending temperature and record results 10. Repeat with different concentrations Attempts Concentration of HCl (M) Time taken for 10% decrease in LUX (seconds) Volume of HCl/STs (ml�) Starting Temp. (�C) Ending Temp (�C) Starting light intensity (%) Ending light intensity (%) 1 2 3 Average 0.25 48.53 54.53 51.28 51.45 20 28 29 28 28.3 29 27 28 28 80 70 1 2 3 Average 0.50 35.78 38.37 43.19 39.11 20 27 28 28 27.7 28 28 27 27.7 80 70 1 2 3 Average 1.00 33.18 34.72 33.91 33.94 20 28 27 29 28 29 28 27 28 80 70 1 2 3 Average 1.25 42.37 45.24 ...read more.


The graph shows that the time rapidly decreased after the first concentration but then over the next three concentrations only gradually decreased and then on the final concentration rapidly decreased again. The results however didn't fit that neatly into the line of best fit but they are clear and easy to understand. There were some anomalies within the experiment and this may have been caused by the stirring or the timer being started and stopped wrongly. I think that our group had a good method because our results showed what we were trying to find out, which was to test how the change of concentration affects a reaction. To get rid of any anomalies we could have either not stir the mixture or use a machine to stir it at the same speed each time. I think that the procedure that we had used was adequate to test and that it was reasonably reliable. In my prediction I had stated that as the concentration increases, the time taken for a 10% decrease in light intensity would decrease.This is because more particles would be in the higher concentration causing more effective collisions to happen. In future experiments we could increase the range of results as well as having more intermediate values. Ricky Pitt 1180 Edenham High School 14320 ...read more.

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