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The effect of concentration on the rate of reaction

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The effect of concentration on the rate of reaction General Introduction In the reaction between hydrochloric acid and magnesium ribbon, the hydrochloric acid will dissolve the magnesium and produce hydrogen gas. All chemical reactions involve reactants which when mixed may cause a chemical reaction which will make products. In my case the reactants are hydrochloric acid and magnesium ribbon. The chemical reaction takes place when the magnesium ribbon is dropped into the hydrochloric acid. The products that are formed during this reaction are hydrogen gas and magnesium chloride. The formula equation for this experiment is: Mg + 2HCl > MgCl2 + H2 Magnesium will react with hydrochloric acid, because it is higher in the reactivity series that hydrogen. When the two chemicals react a displacement reaction will take place and the magnesium will displace the hydrogen in the hydrochloric acid forming magnesium chloride and hydrogen gas. The general aim of this experiment is to discover how the concentration of hydrochloric acid affects the rate of reaction of a piece of magnesium ribbon. In this experiment the factor we are going to change is the concentration of the acid. We will do this, by using five different concentrations, and record the time each takes to react with a piece of magnesium ribbon. The concentration of the acid will be measured in molars/dm3, and will consist of: 0.5 1.0 1.5 Mol/dm3 2.0 2.5 We will be taking all the necessary precautions e.g. ...read more.


If there is still some magnesium left over when it has stopped effervescing then I will have to increase the volume of hydrochloric acid. If the reaction takes too long to finish then I will have to shorten the length of magnesium that I use, however if the reaction is too short then I will have to do the opposite and increase the length of magnesium that I use. The optimum rate that I am trying to find is a reaction that isn't too short but isn't too long, so I can get enough results to plot a good graph. I need to find the optimum volume of hydrochloric acid so that it is in excess after the reaction is over. Apart from trying to find the optimum rate of reaction I also have to find out how to keep the temperature change down. This is because as the reaction is taking place the temperature will rise because the reaction is exothermic, and this could cause my results to be inaccurate as the temperature change will heat up the acid and give the acid particles more energy so they will move faster and collide with the magnesium with greater force causing more successful collisions per second. Preliminary Results Below are two tables: in the first one we were trying to decide the amount of HCl to use, and in the second we were trying to discover the most appropriate size of Magnesium ribbon to utilize. ...read more.


HCL Particle Magnesium Particle Particles of the same substance colliding (Causes the rate at which the particles react to decrease) Evaluation Overall I feel that I was rather precise and accurate in recording measurements. Although there were a few inaccurate results. I obtained two anomalous results. The first one being the 0.5 concentration on the first set of results. This could have happened by mistakenly placing the wrong size magnesium into the test tube or cutting the magnesium to the wrong size. The second error being the average for 0.5. But this was probably affected by the mistake in the first set of results. These errors both occurred in the first run, when my techniques and practical skills had not been perfected over a large number of experiments! There is also one main factor that could have been controlled better, the temperature. As the weather changes dramatically every day in Wales the temperature often varied, therefore affecting the reaction times. We could have used Bunsen burners etc. to solve this problem. We could also have carried out more pre-tests to ensure that everything had been thoroughly tested. This would have given us a wider variety of results. (Encarta: We could have also used different substances. If there were similar results for these materials then we would be certain that concentration does have an effect on the rate of reaction.) So, this shows us that the collision theory, on which this experiment and my prediction were based, is correct! Concentration does affect the rate of reaction! __________________________ 1 ...read more.

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