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Investigate how the concentration of sodium thiosulphate solution affects the rate of reaction between it and hydrochloric acid.

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Introduction

Chemistry Coursework - Rate of Reaction Aim To investigate how the concentration of sodium thiosulphate solution affects the rate of reaction between it and hydrochloric acid. Hypothesis I predict that with an increase in concentration of sodium thiosulphate will come an increase in reaction rate. I base my prediction on the collision theory, a successful collision being when two particles collide such that they react with one and other. I have chosen to investigate how concentration affects reaction rate, there are three other aspects which can also effect rate of reaction. * Temperature - The higher the temperature the more energy is gained by particles and so the faster they collide * Particle size (surface area) - The larger the surface area the more exposure to the reactant and so the faster the reaction * Catalysts - A catalyst lowers the activation energy of a substance, meaning particles gain more energy and so move faster, and collide successfully. ...read more.

Middle

40 32 24 16 8 * Pour the first of the above concentrations into the conical flask * Pour 5cm3 of Hydrochloric acid (2M) into the flask with the sodium thiosulphate solution and start the stopwatch * Swirl the mixture gently as you time the reaction * Stop the stopwatch when you are no longer able to see the cross on the piece of paper, as the mixture has become too cloudy To check the experiment was performed fairly I ensured: - The volume of hydrochloric acid was always 5cm3 - The temperature was constant - The experiment was repeated 3 times for each concentration of sodium thiosulphate and an average result taken to improve accuracy. Trial Run I chose to do a trial run to test my method. ...read more.

Conclusion

I was careful when measuring out the concentrations of sodium thiosulphate and in recording the time. The only result that might be considered an anomalie is the 8g/l solution and those that make up the average. Human error aside however it is likely that this is because there are fewer sodium thiosulphate particles to collide and so the repeat measurements may vary more. If I had the opportunity I might redo the 8g/l concentration to improve accuracy. The method is simple to follow and I tried to take my time with readings etc to minimise the change of human error. To make it easier to measure out the acid/thiosulphate solution I could use a syringe or large dropper. My results support my prediction so I feel they are reliable, although repeating the experiment more might improve reliability. The only thing I do keep in mind about the results is that they are averages not actual readings. ...read more.

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