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What factors affect the rate of a chemical reaction?

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What factors affect the rate of a chemical reaction? Plan I am going to investigate the reaction between sodium thiosulphate and dilute hydrochloric acid. The rate of this reaction can be changed by a number of things: * The temperature * The use of a catalyst in the reaction * The surface area (Of solid reactants) * The concentration of the reactants I will investigate the effect of varying the concentration of Sodium thiosulphate solution in a reaction with Hydrochloric Acid. In my preliminary tests I found that a mixture of Sodium thiosulphate and water totalling 50cm� mixed with 10cm� of Hydrochloric acid worked at the right type of speed for the time I have to do my experiment in, so these are the amounts I will use in the experiment. When sodium thiosulphate and hydrochloric acid are mixed together, yellowish sulphur is formed in the liquid, making the clear liquids cloud over. This is the equation for the reaction: Sodium Thiosulphate + Hydrochloric acid Sodium chloride + Sulphur Chloride + Sulphur + Water Na S O + 2HCl 2NaCl + SO + S + H O I will measure the rate of this reaction by placing 10cm� of hydrochloric acid in a conical flask. ...read more.


* Taking care when handling chemicals, particularly Hydrochloric acid and Sodium Thiosulphate because they are irritants. * Taking care when using glassware to prevent injury. Looking at my plans, I can now make a prediction about what will happen as I change the concentration of sodium thiosulphate. I predict that as the concentration rises, the faster the reaction between Sodium Thiosulphate and Hydrochloric Acid will occur. I know that if there are more successful collisions between the molecules in the mixture the faster the chemicals will react. I also know from a secondary source (Lansdale Science Revision Guide) that the higher the concentration of a chemical the more molecules there are. If there are more molecules in the mixture there will be more successful collisions, meaning the mixture will react quicker as the concentration rises. Results Below are the results I have gained from the experiment: Sodium Thiosulphate (cm�) Water (cm�) Reaction Time 1 (Seconds) Reaction Time 2 (Seconds) Reaction Time 3 (Seconds) Reaction Time Average (Seconds) 10 40 187 178 180 182 20 30 85 85 87 86 30 20 58 53 55 55 40 10 38 39 41 39 50 0 29 29 28 29 To get these results I used the experiment explained in my plan. ...read more.


No results showed up as odd so I didn't need to repeat any of the results because of it being odd. All though I tried to make the experiment as fair as possible, there could be a lot of human error in this experiment. This is when measuring the liquids and looking for an end point in the reaction. The end point of the experiment is when the cross is not visible anymore though the mixture, but this can't be done exactly because it can depend on the person's eyesight etc. To make it more efficient with no human error a light gate can be used to detect when the light doesn't pass through any longer, and it can also use the data to produce graphs and tables on a computer. I could also use more precise measurement tools. To improve the experiment I could go on to try and do lots more different concentrations. I could change other things like, temperature or by adding a catalyst, and see what effects it would have on the reaction rate. If I had time I could go on and do those things but I only had enough time to do the experiment that I have done. ...read more.

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