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Rate of reaction

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Mr. McGeorge - Blue June-July 2004 Plan Aim In my investigation I am trying to find out how concentration affects the rate of reaction. Introduction In my experiment I intend to see how long it takes for a solution of Hydrochloric acid and Sodium Thiosulphate to go cloudy. Then I will dilute the Sodium Thiosulphate by adding water. However I will keep the concentration of Hydrochloric acid the same. I will check to see how this affects my experiment. Here is the word equation for my experiment below. Sodium + Sulphuric Sodium + Sulphur + Sulphur + Water Thiosulphate Acid Sulphate Dioxide Here is the symbol equation for my experiment. Na S O + H SO Na SO +SO +S+H O I will know if my reaction is working because the water will go cloudy. Preliminary Work For my preliminary work I did my experiment at the following concentrations. Concentration of Thiosulphate (ml) Concentration of Water (ml) Amount of Hydrochloric acid (ml) 50 0 10 40 10 10 30 20 10 20 30 10 10 40 10 I did this to see if any of my concentrations were too quick or took too long. Here are my preliminary results. Concentration of Thiosulphate (ml) Concentration of Water (ml) ...read more.


To make it a fair test I will keep the amount of Hydrochloric acid the same because this is the control of the experiment. I will measure it with a small measuring cylinder because they are more accurate than the larger measuring cylinders. If I were to change the temperature then it would spoil my results because of the kinetic theory. For reliability I will repeat the test at each concentration three times then take an average of the three results. Prediction I predict that as the concentration of Sodium Thiosulphate decreases then the time taken for the solution to go cloudy will increase. I think this because if there are more Sodium Thiosulphate particles then they will have more of a chance of colliding with the particles of Hydrochloric acid so the solution will go cloudy quicker. If the Sodium Thiosulphate is diluted with water then it will take longer for the solution to go cloudy, as there will be less Sodium Thiosulphate particles to react with the Hydrochloric acid particles. I will test my prediction. Results Here are the results of my experiment. Concentration of Sodium Thiosulphate (ml) Concentration of Water (ml) Time 1 (seconds) Time 2 (seconds) Time 3 (seconds) Average time (seconds) ...read more.


I measured the rate of reaction by putting a cross on a piece of paper and when I could no longer see the cross because the solution was too cloudy I stopped the timer. The time on the stopwatch was the rate of reaction. To improve my experiment I could have changed the concentration of the acid. This would have improved the test because it would give me results and information about the test. The concentration I would use for the hydrochloric acid would be 20ml each time. I would do this to see how it would affect my experiment. Reliability of the Evidence My test was fair because I kept the amount of Hydrochloric acid the same throughout the experiment. This was the control of the experiment. I also controlled the independent variable, the Sodium Thiosulphate, by measuring it carefully and accurately. In my experiment I did not have any anomalous results. This is shown as my graph goes down in a curve, which is what it should do. I think that I do have enough data to get accurate results, however if I had done some more tests at different concentrations it would have made it more accurate. If I had done the same tests again I believe I would get similar results. To improve my method and the reliability of my experiment I could have used a thermometer to keep the temperature the same, because temperature affects the rate of reaction. ...read more.

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