Rate of Reaction Experiment

Rate of Reaction Experiment
Rate of Reaction Experiment The aim of this investigation is to discover how a varying temperature affects the rate of reaction between sodium thiosulphate and hydrochloric acid. The reaction I will be testing is: Na2S2O3 + 2HCl à 2NaCl + H2O + S02 + S Sodium thiosulphate + Hydrochloric acid à Sodium chloride + water + Sulphur dioxide + Sulphur I aim to find this by running a series of experiments, gradually increasing the temperature for different tests. To make this a fair investigation, I will have to keep all other variables as constant as possible. These variables include: - concentration - volume - light I will also have to control human input ? even though I will be able to keep most variables in my investigation constant, different people may measure the volumes slightly differently. Because of this, I will make sure that the same person measures out the volumes of the substances for each test. Prediction I predict that the amount of sulphur produced in a certain amount of time in this reaction will increase as the temperature increases. It is the sulphur that turns the reaction cloudy. I shall time how long it takes to produce a certain amount of sulphur at different temperatures.
Scientific Reason I believe that the rate of reaction will increase as the temperature of the reactants increase due to ?collision theory?. A rise in temperature will increase the rate of most chemical reactions; a fall in temperature slows them down. As the rate of reaction depends on how many and how often useful collisions occur, this means the more often collisions occur, the faster the reaction will be. As the reactants are heated, the particles gain more energy and move about more. This creates a greater chance of effective collisions, so the rate of reaction increases. The Q10 law states that, in most cases, a rise of 10˚C doubles the rate of reaction. Method and Equipment Equipment - 300cm³ Sodium Thiosulphate - 75cm³ Hydrochloric acid - Beaker - Bunsen burner, heat proof mat, tripod & gauze - Thermometer - 2 Measuring cylinders (narrower ones are more accurate) - Piece of paper with black dot on. - Stopclock. - Boiling tube Method - Set up equipment: Each test requires: 1. 20cm³ sodium thiosulphate 2. 5cm² hydrochloric acid - Heat sodium thiosulphate to one of the five temperatures: room temperature (23ºC), 28ºC, 33ºC, 38ºC, 43ºC. I have selected to use these temperatures to show quite a large range of results, and so that changes and patterns in reaction rate can be easily analysed. If I went up in tens of degrees Celsius, my results would have been too widespread and my analysis would have been very vague. However, if I went up in twos, the analysis would have been very precise, but the range of results would have been very small. - Combine the sodium thiosulphate with the hydrochloric acid, and record how long it takes for the black dot on the paper to be obscured from view. Na2S2O3 + 2HCl à 2NaCl + H2O + S02 + S It is the ?S? (sulphur) that turns the reaction cloudy. When so much sulphur is produced that the black spot is obscured from view, I shall stop the timer. As temperature shall be my only variable, I shall keep the other variables, such as concentration and volume, as constant as possible, to make this a fair test. Results Temp. (ºC) Time (seconds) 1 2 3 Average 23 45.72 41.17 43.94 43.61 28 39.95 31.39 34.04 32.46 33 23.37 24.27 27.66 25.10 38 24.93 20.08 22.92 22.64 42 17.98 16.52 15.28 16.59 From my graph and results I have found that the temperature of the reactants is inversely proportional to the time it takes for the reaction to occur. I predict that the temperature of the reactants will be proportional to 1/time. Temp. (ºC) Time (Avg.) 1/time 23 43.61 0.023 28 32.46 0.031 33 25.10 0.040 38 22.64 0.044 43 16.59 0.060 This graph shows that my prediction was correct ? the temperature of the reactants is proportional to 1/time. From these results I have found that my prediction was correct ? As the temperature of the reactants increases, the time for the reaction to occur decreases. As the temperature increased by 10ºC, the time taken was almost halved. Eg. ? 20ºC ? 54s. 30ºC ? 30s. I predicted believe that the rate of reaction would increase as the temperature of the reactants increase ? by drawing two graphs I have proved that my prediction was correct, although if more care was taken, a more strict rule could have been found. Evaluation I feel my results were reasonably reliable. The scatter in my graphs was small, and there was only one slightly anomalous result. This result may have been anomalous for a variety of reasons ? the temperature may have been too high or low, the volume of either the hydrochloric acid or the sodium thiosulphate may have been inaccurate, or the timekeeping may have been inaccurate. If I repeated this experiment, I could improve it by being more accurate with the volumes of the reactants, by using narrower measuring cylinders. I could regulate the temperature more accurately by heating both substances in a water bath. I could further this experiment by testing different temperatures, concentrations, different volumes of the reactants or even by using different types of acid, to see if the same pattern applies. I believe I have carried out this investigation to the best of my ability and as accurately as I could in a school laboratory environment.

Rate of Reaction Experiment 9.2 of 10 on the basis of 1889 Review.