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Rate of reaction

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Background We place the reaction mixture on a paper with a black cross-drawn on it. When the cross is completely obscured, the reaction will have finished. The time taken for this to happen is the measure of the rate of reaction. We must do this several times, and change the concentration of sodium thiosulphate. The rate of reaction is a measure of the change that happens during a reaction in a single unit of time. The things that affect the rate of reaction are as follows: � Surface area of the reactants � Concentration of the reactants � The temperature at which the reaction is carried out � Light � Use of a catalyst Rate of reaction = I/T The factor, which we are using, is Concentration of the reactants. Temperature Increasing the temperature of a reaction increases the rate of a reaction. At the higher temperatures reactant particles move faster and collide more often and more violently. Increasing the temperature will cause the particles to move faster with more energy. They will therefore collide. If they have more energy they will collide with grater force this means there is more successful collision per second and therefore a faster rate of reaction. Surface Area Breaking up solids into smaller pieces increases reaction rate because this increases the total surface area. Increasing the surface area must increase the number of particles of the solid in contact with the other reactant in solution. Catalyst Using a catalyst increases the rate of a reaction. ...read more.


If the volume is different, then it could give different results to if it was at a constant volume. We must also make sure that we add both the water and the sodium thiosulphate at exactly the same time (into the conical flask with the hydrochloric acid in it), or it could effect the results of the experiment. We must start the stopwatch at the exact time as we put the water and the sodium thiosulphate into the conical flask. To do this it is a lot easier if there are two or more people doing the experiment, so one person can put the two substances in the HCL, and one person can start the stop watch. Another thing we must do is to make sure that the conical flask is completely clean and free of any water or any other substance before we attempt to start the next experiment. We must also make sure that the measurements are as accurate as we can make them. Also we will have the same person deciding when the cross cant be seen this will illuminate any augment's about when the cross can be seen. To make it a fair test we will make sure that the temperature is the same when the experiment is taking place. To make the results true we will try and make sure that there are no catalysts in the solutions. Also we will try and keep the surface area the same. Apparatus * Conical flask * Sodium thiosulphate (different concentrations) ...read more.


Which would mean the range of results would be lower which would mean the pattern we got would be less obvious. The experiments were fair tests to a certain extent but there was a certain margin of error. This was because the results recorded were only to the nearest cm� and the values of the controlled variables were not exact amounts so the may have been slightly differently each time which would have affected slightly the reliability of the results. This would have made little difference to the results though as the volume of solutions were only measured to the nearest cm�. To find if the prediction was supported or to find if the reaction rate was faster when the concentration increased we could have changed the constant and seen how the concentration of the new acid affected the rate of reaction. If we was to do the experiment again we would have like to extend the experiment and seen what other variables affect the rate of reaction for example we would have like to investigated if changing the temperature would effect the rate of reaction. From looking at our background work I can clearly see that the higher the temperature there faster the rate of reaction. Also another thing which I would have like to investigate if the experiment was done again is how catalyst effect the rate of reaction I think that this would have been more interesting and more challenging for me and my group. . ...read more.

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