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Sodium Thiosulphate + Hydrochloric Acid Coursework

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Sodium Thiosulphate + Hydrochloric Acid Coursework Plan Aim I must produce a piece of coursework investigating the rates of reaction when Sodium Thiosulphate + Hydrochloric Acid are mixed. The reaction that will be used is: Na S O + 2CHl 2Na Cl + S + SO + H O Sodium + Hydrochloric Sodium + Sulphur + Sulphur + Water Thioslphte Acid Chloride Dioxide Variables Other variables, which may affect the outcome of this experiment, if not kept constant, are as follows: o Temperature of liquids. I believe that the hotter the temperature, the faster the rate of reaction. This is because when a substance is heated up, each particle has more energy, resulting in more collisions between the free moving particles in a liquid, causing more particles to react, therefore increasing the overall rate of reaction. The second effect this has is that the particles collide with more force, increasing the chance of the particles reacting. I will keep this variable constant so that it does not affect the results by avoiding heating the sodium thiosulphate in any way, and so it will stay at room temperature. o Human Error/People. This experiment relays on people and their eye sight, because to determine how long the reaction takes a cross is put under the container and when it isn't disappears the timer is stopped and the time is taken down. ...read more.


Method Firstly, I will dilute the Hydrochloric Acid by way of ratios (see diagram 1) I will measure 10cm� of solution each time, with a burette, but I will vary the volume of Hydrochloric Acid compared to the volume of water diluting it, making different concentrations of Hydrochloric Acid. I have found from preliminary tests that these concentrations react at rates which I can measure quite accurately with the equipment I have. Then, I will take a cross which I have ready made on the computer, and place it underneath a flask/container. Into the conical flask, I will pour the 10cm� of sodium thiosulphate solution and 10cm� of hydrochloric acid, and start the stop clock as soon as all the solution has been added. When the mixture has become opaque, or when the cross underneath the flask isn't visible any longer, I will stop the clock and record how long it has taken to reach this stage. I will repeat this 3 times with each concentration, making sure that the conical flask is fully washed out, because I will be using the same flask every time, so that the flask does not introduce any new variables into the results. To find a rate of reaction from the results I will collect, I will divide 1 by the time in seconds. ...read more.


From this, I can speculate that the experiment was conducted well, and that the results have only been affected by other variables by little or no amount. However, looking at the graph, I can see that there is a result that do not follow the general trend, and show a higher rate of reaction than would be expected at that point. I believe that perhaps this was caused by a change in another variable I remember I had wash out the flash with hot water and so the partials had more energy and collide more to speed up the reaction time. I think that the only flaws in the experiment were the washing the flash with hot water and in the judging of when the reaction had completed. If I was to repeat the experiment, I would find a completely different way of measuring when the reaction has completed. Perhaps some sort of electronic device could detect turbidity more precisely. This device could shine a bright light, perhaps a laser through the chemicals, to be received by a very sensitive LED on the other side. This LED could be connected to a stop clock which would stop once the LED stopped receiving direct light (it would still be able to detect some light, but it would not be direct because it would be diffused by the turbidity of the chemicals). ...read more.

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