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The effect of concentration on rate

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Chemistry Coursework The effect of concentration on rate of reaction By Gavin Teggart Pupil Planning Sheet AT1 Investigating in Science Name Gavin Teggart Candidate No. Centre No 71761 Investigation Title The effect of concentration on the rate of reaction between Sodium Thiosulphate + Hydrochloric Acid 1) What am I trying to find out? I am trying to find out how concentration affects the rate of reaction. 2) What do you think will happen? (Prediction) I predict that the speed of reaction will increase as the concentration is increased. E.g. If I increase the particle amount I should get more reactions as it increases the chances of the particles colliding with each other. 3) What will I have to alter? I will alter the amount of sodium thiosulphate. 4) What will I have to keep the same in order to have a fair test? To make my test a fair one I will have use the same amount of Sodium Thiosulphate and I will also need to use the same amount of acid in my experiment. 5) What measurements will I have to take? In my experiment I am going to record certain measurements I will first take the measurements of the volume of sodium thiosulphate used. Next I will record the volume of acid, I will also take measurements of the amount of water added to the solution and lastly I will record the time taken for X to disappear completely. ...read more.


Chemical reactions happen all around us when we light a match, start a car. They happen when particles hit into each other this will start a chemical reaction. My prediction is that if the sodium thiosulphate has an increased concentration the reaction will be faster so the sulphur will be made faster. This happens because the sodium thiosulphate has more particles hitting of each other this is because the solution is more concentrated therefore the reaction takes place quicker Apparatus Sodium Thiosulphate HCl Conical flask Water Measuring cylinders 10ml, 50ml Stop clock White paper with an X marked on it Method I marked an X in the centre of a piece of white paper with a pencil I then placed a conical flask on top of the paper Using a 50ml measuring cylinder 50ml of Sodium Thiosulphate is put into the flask then I add 10 ml of HCl acid to the flask I started the stop watch and as the reaction takes place watched the X on the paper disappear. I recorded the time it takes for the X to disappear. I repeated the experiment two more times to make my test fair. Then I repeated the experiment again using different amounts of sodium thiosulphate and Hydrochloric acid, the amounts are in my table I used the results of the test to make a line graph I will carry out the experiment in a certain way that will give me my results that I need for my investigation. ...read more.


I think my results are accurate. Explaining Rates The Collision theory says that for a reaction to take place the reacting particles must: 1) collide with each other 2) the collision must have enough energy called the activation energy to be successful. The particles in solution move around constantly. Here an acid particle is about to collide with a Sodium Thiosulphate particle. If the collision has enough Activation Energy a reaction takes place and Sulphur begins to appear. If the collision does not have enough energy then no reaction will take place. If there are lots of successful collisions in a given unit of time then a lot of Sulphur is produced in that minute. The reaction can be described as fast. If there are not as many successful collisions then the rate at which Sulphur is produced is low and the reaction is described as slow. Why reaction rate changes with concentration If the concentration of the Sodium Thiosulphate changes the speed of the reaction changes. In dilute Sodium Thiosulphate there are not so many Sodium Thiosulphate particles. This means that there is not much chance of an acid particle and a Sodium Thiosulphate particle colliding so the production of the Sulphur is slow Here the Sodium Thiosulphate is more concentrated. This means there are more Sodium Thiosulphate particles in the solution. There is now a greater chance of a successful collision occurring and so Sulphur is produced quickly, The reaction is fast. ...read more.

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