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The purpose of this experiment is to see how the concentration of hydrochloric acid affects the rate of reaction when mixed with sodium thiosulphate.

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Friday 28th November Chemistry Coursework Aim The purpose of this experiment is to see how the concentration of hydrochloric acid affects the rate of reaction when mixed with sodium thiosulphate. Introduction I have been assigned the task of recording, and understanding how the concentration of acids affects their rate of reaction. The experiment will be conducted under the rules of a fair test and will involve mixing sodium thiosulphate with different concentrations of hydrochloric acid. The solution, stored in a beaker, would then be placed above a light sensor, which would then record the amount of light passing through the solution. Once the light sensor takes a final, definite reading this indicates that the reaction has finished. I then have to record the time, in which the solution turns misty restricting light from reaching the sensor and also record the percentage of light reaching the sensor as well. In my coursework I should include: * How the preliminary experiment is done, and the results recorded. * Give a detailed prediction. * List all the appropriate materials used. * Write out a step-to-step method of how to conduct the experiment. * Include an analysis with graphs and explanations to results. * An evaluation with links to defaults in methods, results. Conducting a Fair and Safe Test The most essential precautions to achieving accurate results is in making sure that the experiment is a fair test, with all the variables thought of. I will make my results accurate by making sure that the solutions are measured correctly and the same amount is used of each. I will also do a number of trails to obtain an average, that way my results will be as accurate as possible. The independent variable (what I'm changing) in my experiment is the concentration of hydrochloric acid. The concentrations used will be 0.25, 0.5, 1.0, 1.25, 1.5, 2.0 and will be measured in molars (M). ...read more.


In many reactions, the particles already have this energy and react straight away. In others, energy has to be supplied for the particles to reach activation energy. When the sets of particles have this energy, which they get from the light turning into heat energy, they use it to collide with one another to break the ionic bond in sodium thiosulphate. Then once the bond is broken the particle collide to make new bonds. When this happens ions from the breaking of the ionic compound found in sodium thiosulpahte are left floating around freely in the solution. The new bond that is made is in fact sulphur and that sulphur is used to blot out the light to the sensor and the 10% decrease in light intensity is used to determine when the reaction is complete. Equipment I will be using a number of instruments and solutions to conduct my experiment and they include: * Sodium thiosulphte * Hydrochloric acid (0.25, 0.5, 1.0, 1.25, 1.5,2.0) * Light sensor * Stop clock * 2 measuring cylinders * Thermometer * Beaker * Stand with clamps Method 1. Gather all equipment and solution for the experiment. 2. Pour 20cm� of sodium thiosulphate in to a measuring cylinder and then pour 20cm� of hydrochloric acid (0.25m) in a separate cylinder. 3. Set up the light sensor apparatus. Then place the glass beaker directly over it. 4. Now place a thermometer in the beaker and make sure the stop clock is set to start. 5. Pour both hydrochloric acid (0.25m) and sodium thiosulphate into the beaker at the same time and record the temperature instantly, whilst starting the clock as well. (It is advised to use more than one to conduct this stage.) 6. Once the solution turns cloudy and the light sensor takes a definite reading after decreasing by 10% stop the clock and record the time, also check and record the temperature reading, and the light reading as well. ...read more.


I would make the concentrations closer together as this would show the results more clearer. Doing this would allow me to see the results trend even clearer and therefore produce an even more accurate line of best fit. I would also make the range of concentrations even bigger as to see if the results would continue to level off. I would also think about carrying the experiment out with other reactants to she if the pattern would be the same. When looking at my results you notice that they are not of a superior quality. There is minor consistency in the repeats and no real pattern in a series of results. I feel if I was to cancel out the problem of not cleaning the apparatus to late in the experiment then my anomalies would be non-existent. The range of my results seem fine as they prove my theory and show that my prediction was correct, although to include more concentrations in the experiment would be a lot better as to see if the results continue to level off. If I were going to extend the experiment then I would start by introducing different types of acid to the experiment. I would do this as to see if concentrating different acids would affect rate of reaction and also see if concentrating the different acid have an effect. I would also increase the range of concentration and make the concentrations even more close together. I would do this as to see if the line of best fit could be even more accurate and also see if the results would continue to level off. I would also extend the experiment by seeing how heat affects rate of reaction and see if all acids are affected. I would also like to see how rate of reaction would change depending on altering the strength of the light. I would do this as to see how much heat is produced by different strength light bulbs. Terry Cave Edenham High School Chemistry Coursework Ms. Cheung Terry Cave 10.8 Ms. Cheung Chemistry Coursework Candidate Number: 1054 ...read more.

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