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GCSE Chemistry Coursework on Rates of Reaction

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This piece of coursework investigates rate of reaction. I will investigate how concentration of a solution affects the rate of reaction. I will be carrying out the experiment in which sodium thiosulphate solution (of different concentrations) is mixed with dilute hydrochloric acid. When these solutions are mixed and they react, a precipitate (meaning solid) of sulphur forms. This solid turns the liquid translucent. The time taken for a certain amount of sulphur to form can indicate the rate of reaction. Once my two solutions are mixed I will use a stopwatch and record how much time it takes until I can no longer see a black cross beneath the beaker. My variable will be the concentration of the sodium thiosulphate needed to react with the hydrochloric acid. I will vary the concentration by adding different proportions of water to the sodium thiosulphate to dilute it. Na2S2O3 + 2HCl 2NaCl + SO2 + H20 + S (aq) (aq) (aq) (g) (l) (s) Sodium + Hydrochloric Sodium + Sulphur + Water + Sulphur Thiosulphate Acid Chloride Dioxide Backround Knowledge Rate of Reaction: This is the speed at which a reaction takes place. The chemical definition of rate of reaction is: the rate of chemical reaction as the change in concentration of one of the reactants or products in unit time. The effect of Concentration If the concentration of any reactant in a solution is increased, the rate of reaction is increased. ...read more.


They have the advantage of bringing about reactions at normal temperatures and pressures which would otherwise need more expensive and energy-demanding equipment. In my experiment; I will be focusing on the effect of the concentration of a substance in the reaction. The rates of chemical reactions can vary greatly. For example: a really fast reaction would be when a chemical explodes-its rate would be very fast, however there are reactions that could take months or even years, this would be like rust forming. Prediction Reactions occur when the particles in the solutions collide. From past experiments, I can predict that the stronger the concentration of hydrochloric acid, the shorter length of time it will take for the cross to disappear. I make this prediction as I know that stronger concentrations contain more of the Na2S2O3 particles and so increase the probability of collisions occurring and again increase the chance of the reaction occurring faster. Variables Volumes of original sodium Thiosulpahte Volumes of water added. Concentration=Volumes of original solution /30 X40 Concentration (g/dm3) 30 0 30/30 x40=40 40 25 5 25/30 x40=33.3 33.3 20 10 20/30 x40=26/7 26.7 15 15 15/30 x40=20 20 10 20 10/30 x4013.3 13.3 5 25 5/30 x40=6.7 6.7 I understand that there are many factors which can affect the accuracy of my results so I will ensure that I keep all the physical conditions the same for my experiments. ...read more.


Conclusion I think that as the concentration increased the rate of reaction also increased this down to the reactant particles in concentrated solutions. I am going to refer back to my background info to come up with the final conclusion. I previously stated that in concentrated solutions there are more reactant particles per unit volume and therefore more collisions between the reactant particles, this increases the rate of reaction. So increasing the concentration, it would lead to more collisions and maybe even with greater force. The collisions explains how chemical reactions occur, it states that reactions can only happen when the reactant particles collide, so there will be more chance of fruitful collision. E.g. if the was double the amount of concentration, it would mean double the amount of reactant particles! So more collisions will take place so the reaction will be over quicker. I believe my method was the best way of doing the investigation-because I did the experiment twice to gain more accurate results. However if I were to do the experiment again, the changes I would make are as follows: I would us more accurate means of measuring my solutions and by using dry conical flasks for each experiment. I would change these as this could again improve accuracy. I do not believe that my results were accurate enough, however I do believe that they clearly show a correlation and prove a theory. ?? ?? ?? ?? GCSE Chemistry DA - Coursework on Rates of Reaction - 1 - ...read more.

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