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An investigation on the rates of reaction

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An investigation on the rates of reaction I plan to carry out an experiment to investigate the rates of reaction when hydrochloric acid is added to sodium thiosulphate. The rate of reaction depends on different factors. These are the main factors: Temperature Stirring or shaking the solution Concentrations Adding a catalyst I have chosen to change the concentrations and the temperature because it will be easier to measure and the results will be more accurate. Diagram: This is the word equation for the experiment: Sodium thiosulphate + hydrochloric acid sodium chloride + sulphur dioxide + water + sulphur The symbol equation: Na S O + 2HCl 2NaCl + H O + SO +S Fair test 1: Fix: The amounts of hydrochloric acid and sodium thiosulphate used The concentration of the hydrochloric acid The temperature of the solution Measure: The time taken for the solution to become so misty the cross is no longer visible Change: The concentration of the sodium thiosulphate Fair test 2 Fix: The amounts of hydrochloric acid and sodium thiosulphate used The concentration of the hydrochloric acid and sodium thiosulphate Measure: The time taken for the solution to become so misty the cross is no longer visible The temperature of the solution Change: The temperature of the solution Apparatus: Conical flask, hydrocloric acid (50g/dm3) in liquid because it will be easier to record, sodium thiosulphate (different concentrations) in liquid, small beaker, large beaker, small measuring cylinder, large measuring cylinder, funnel, thermometer, stopwatch, tile with a black cross on it, bunsen burner, tripod, gauze, mat, apron and goggles. ...read more.


When the temperature is increased the more kinetic energy the particles have, they move faster. Therefore: There are more collisions The collisions are more vigorous and energetic so more of them are successful in breaking the bonds. Prediction: I predict that the more concentrated the solution the faster the reaction because there are more particles for the acid to collide with and as shown in my theory there should be a faster reaction. If the concentration is doubled the amount of reacting particles are doubled therefore the reaction will take half as long and the rate is doubled. E.g. if the solution is 40g/dm3 the rate will be twice as fast as the solution at 20g/dm3. When the temperature increases I predict the particles will have more energy so there will be more collisions which break the bonds resulting in a faster reaction. When the temperature is increased by 10?C the number of molecules with activation energy (according to the Maxwell-Boltzmann distribution curves) will double. Therefore the rate of reaction will double. Results: Rate and time are inversely porportional. The rate is worked out by 1/time. The rate is multiplied by 1000 so it is easier to put on the graph with simpler numbers. Concentration of sodium thiosulphate/ g/dm3 Average time of the two experiments/s Temperature at the end of experiment /?C Rate x 1000/ s-1 Time 1 /sec Time 2 /sec 50 32.34 16 30.92 33.48 31.20 40 46.04 16 21.72 46.29 45.79 30 61.82 16 16.16 62.91 60.88 25 78.11 16 12.80 ...read more.


It would have been easier to put it in a water bath because this will make both the solutions at the same temperature, although that would have taken more time. It would have been set up like this: There were two anomalous results on the concentration graph these may have been caused by the fact that some of the experiments were done on different days so the temperature differed by nearly 5?C. My results would be more consistent if I repeated them at the same temperature. When I repeated the experiments they were usually similar to the original measurement. My results were what I expected them to be because as proved in my analysis the rate increased by double when the concentration increased by double as I predicted. When the temperature went up by 10?C the rate doubled as I predicted. The range and accuracy of my results were good enough to draw to a strong conclusion and in both experiments it supports the theory. To improve my conclusion I could do more repeats to make the results more reliable, do a larger range of concentrations e.g. do 60g/dm3 and 70g/dm3 . I could also close the gap between readings, for instance, doing 24?C between 16?C and 32?C and 45g/dm3 between 40g/dm3 and 50g/dm3. This would improve the trends on the graphs. To investigate the topic further I could do another experiment stirring the mixture at different speeds and observing the changes. ?? ?? ?? ?? James Robertson 10S ...read more.

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