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Investigate the effect on varying the concentration on the rate of reaction between sodium thiosulphate solution and dilute hydrochloric acid.

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Chemistry Coursework-Rate Of Reaction Aim Investigate the effect on varying the concentration on the rate of reaction between sodium thiosulphate solution and dilute hydrochloric acid. What is 'rate of reaction'? The rate of reaction tells us how quickly a chemical reaction happens. Reactions happen, no matter what. Chemicals are always combining or breaking down over and over again but not always at the same speed. There are a few things which really affect the speed of the reaction and the number of collisions that can occur. (1) CONCENTRATION: If there is more of a substance in a system there is a higher chance that molecules will collide and speed up the rate of the reaction. If there is less of something, there will be fewer collisions and the reaction will probably happen at a slower speed. (2) TEMPERATURE: When you raise the temperature of a system the molecules bounce around a lot more (because they have more energy). When they bounce around more they are more likely to collide. That means they are also more likely to combine. When you lower the temperature the molecules are slower and collide less. That temperature drop lowers the rate of the reaction. (3) PRESSURE: Pressure effects the rate of reaction especially when you look at gases. When you increase the pressure the molecules have less space to move around. That greater concentration makes them collide with each other more often. When you decrease the pressure molecules don't hit each other as much and there are fewer collisions. ...read more.


40 57.05 55.89 56.47 10 40 5 20 210.66 215.24 212.95 Conclusion I have got my results (above), and I have decided that the best concerntration to use for my final experiment will be 20%. This reaction won't happen to quickly. Actual Investigation Factors Temperature Surface area Gas Reaction Catalyst Actual Reaction The reaction that I will be using in my experiment will be as follows: Sodium thiosulphate solution (l) + dilute hydrochloric acid (l) � sodium chloride (aq) + water (l) + sulphur dioxide (g) + sulphur (aq) The solutions are both clear when not mixed, but when they are mixed the solution will get cloudy over time because sulphur is produced. Variables Dependant The dependant variable is the time. The times will not change throughout the experiment. I will use a basic stop watch to find the time taken. Independent The independent factor is this experiment is the temperature of the solution, this will vary throughout the experiment. Control I will use the same amount of solution in this experiment and that is 55ml. The sodium thiosulphate and hydrochloric acid will have the same concentration throughout the experiment. Errors I will be doing the experiment over more than 1 lesson, so the equipment and solutions I will use will not be exactly the same. Even the room temperature will change due to people entering and exiting the room. Fair Test I will make sure that I measure all the solutions correctly, if I don't it could cause me to have an inaccurate result. ...read more.


To have made my final experiment better I feel I could have done the test more times, so that I would get a more accurate average result, but I was happy with the results I already had so I felt this was un-necessary. I could have also done the same experiment but changed the temperature, this would have been interesting to see how the results would vary. I think that they would vary a lot because temperature can increase or decrease the rate of reaction massively. I followed all the safety rules that I put down in my preliminary work and final experiment work, this is always going to be important because I didn't want anyone to get harmed. I used all the help sheets provided to make sure that I was doing all the necessary procedures correctly. I repeated the test 3 times so that I could get good average results. If I had another chance I would have done the experiments all on the same day, but as I stated early unfortunately time wasn't on my side completely. To ensure that I got all the measurements right I had to keep re-measuring the solutions, it was time consuming but it was worth it, the results I have reflect that, I also always got a second opinion, so I could be sure that I was using nearly the perfect amount. If I had to extend this investigation I feel it would be most interesting if I changed the actual surrounding temperature, I could do the experiment in the class and outside, seeing how the surrounding environment affects the rate of reaction. ...read more.

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