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Rates of reaction

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Rates of Reaction Plan The aim of this investigation is to find out how the concentration of sodium thiosulphate affects the rate of reaction when reacted with hydrochloric acid. I will use sodium thiosulphate and hydrochloric acid as my two reactants. I will change the concentration of sodium thiosulphate throughout the experiment and time how long it takes for the sulphur to form. Preliminary Work Preliminary work helps the people conducting the experiment, by seeing if there are any faults in the experiment that they are doing. It helps by making it easier to plan the main experiment. Also if any problems occur during the preliminary experiments, you can find ways of solving these problems during the main experiment. From my preliminary work, I found out essential factors that might affect my results. The consistent pattern I found out from my preliminary work is that, 'the more you increase the concentration of sodium thiosulphate, the quicker the X will disappear under the flask' For particles to react they must collide and due to their being a reduced amount of particles in a dilute solution there is a lower chance of the reaction taking place. For my preliminary work I have come to a conclusion not to record any concentration less than four seconds because this reaction happens too quickly for me to record, stopping my readings from being precise and dependable. I have taken an account of what I have just spoken about and from my surveillance in my preliminary work I will not take account of molars from 1.75 and 2.00. ...read more.


All these factors might change my results, making my investigation to be unfair. It is always the same person recording the time for the X to disappear because other people have a better or worse eyesight and judgement. This will not give me accurate readings because different people have different reaction times. To keep this variable constant, I will use the same observer. The cross is the same. For example, if the cross was not the same throughout the investigation then this might affect the person judgement because another cross might be darker or thicker. This will affect the time for the X to disappear. The flask is washed every time I carry out a new concentration because the flask tends to go cloudy which might affect the person's judgement who recording the time, which may change the rate of reaction. I do not stir or touch the flask while the reaction is taking place because that might affect the rate of reaction. If you touch the flask this may cause the particles to collide more, speeding up the reaction. I will always stay the same distance away from the flask; else it wouldn't be fair, as standing closer would make it easier to see changing my reaction time. Temperature is a variable that has to be controlled because if you increase it, the particles will obtain more energy and this will cause them to move faster, therefore increasing the amount of collisions. It also causes there to be more successful collisions due to the sufficient energy. ...read more.


The higher the concentration the more particles there will be involved causing a higher reaction rate through the collisions of these particle. My results illustrate that the temperature remained around the same throughout the experiment however I had no control over this and it could have caused an error but no anomalous results were found during the experiment. There was little difference between the first set of results and the second set of results which shows that both experiments were successful. I conducted two experiments to get accurate results and then worked out the average results. We used a stopwatch to check how long it took until the x marked on the paper was no longer visible, this indicated how long it took for a reaction to take place. Conclusion The experiment was very successful. My results seem consistent and accurate as the results table and graph show the effect of concentration on a reaction rate. They show the more concentration used the less time it takes for a reaction to take place. All my results fit a pattern. My results seem to be reliable however there were some anomalies. The stop watch has an error of (+ or -) 0.005 seconds however that was the only way we could record the time. The steps that I would take to make sure that my practical was not affected by the factors above would be using a different stop watch or undertaking the experiment in a controlled room temperature. The further work that I would do would be, to add more concentration of sodium thiosulphate to see if the pattern remains constant. ?? ?? ?? ?? ...read more.

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