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The aim of this experiment is to determine whether the concentration of sodium thiosulphate water and hydrochloric acid have any effect on the rate of reaction between the chemicals.

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Aim The aim of this experiment is to determine whether the concentration of sodium thiosulphate water and hydrochloric acid have any effect on the rate of reaction between the chemicals. I believe that the concentration of sodium thiosulphate has a direct effect on the rate at which the reaction occurs. Preliminary work Having used the internet to Research I have found some useful things on rates of reaction. One of those being heat effects the rate of reaction and also the more the concentrated the substance is the more there is to react and therefore the more violently it will react. I'm not sure about the actual rate at which the substance reacts. I also found out that particles only react with each other if they have enough energy to force the reaction this is called activation energy. As water has little or no energy I think this will dilute the substance therefore making it harder and take longer to react. I also think that if I were to dilute the substance enough to a point where the energy would be so little that it would not react at all. Equipment Measuring Cylinders (10CM� and 50CM�), Conical Flask, Paper with X, Beaker of Hydrochloric Acid, Beaker of Sodium Thiosulphate, Stop Clock ...read more.


I will keep this variable constant by using the same conical flask for each experiment. Previous experiments have shown that the size of conical flask I will be using is adequate when gauging turbidity with this volume of chemicals (60cm�). Cross - The material I use draw the cross underneath the conical flask, which I use in determining when the reaction has finished, could affect how easily the cross is seen. This in turn could affect the results because if the cross is seen more easily, if it was drawn with a thick marker, our measurement of how long the reaction took to complete would be longer and so the rate of reaction would seem slower. Equally, if the cross was hard to see, then it would disappear more quickly and the rate of reaction would seem quicker. I will keep this constant by using the same black pen to draw the cross each time, if I are unable to use the same cross each time, which is preferable. Volume Of Sodium Thiosulphate And Hydrochloric Acid - The larger the volume of sodium thiosulphate and/or hydrochloric acid, the greater total number of particles in the solution. ...read more.


Either the reacting mixture was shaken accidentally, moving the molecules around more, increasing their chances of reacting, or more likely, the concentrations of sodium thiosulphate were incorrectly measured, and too much sodium thiosulphate was used. This would reduce the distances between the molecules, and increase the rate of reaction. I think that the only flaws in the experiment were in the measuring of the concentrations, and in the judging of when the reaction had completed. It was very hard to get an exact volume of water/sodium thiosulphate to get the right concentration, and so this may have thrown those three results off the trend. Also, there was not really any sure way of knowing when the reaction had finished. My rudimentary method of looking at the turbidity of the mixture is very inaccurate, and leads to confusion, especially, for example, if you look away for a moment after thinking the reaction is over, and then look again and realise it hasn't. If I was to repeat the experiment, I would use a much more accurate way of measuring the volumes of the reactants, and I would find a completely different way of measuring when the reaction has completed. Perhaps a Light Dependant Resistor could have been connected to a stop clock which would stop once the LDR stopped receiving direct light. ...read more.

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