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Rates of reaction.

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Rates of Reaction Chemistry Coursework Prediction I predict that as the concentration of sodium thiosulphate is lowered the chemical reaction will take longer. By reducing the concentration there will be less particles of sodium thiosulphate in the same volume. This effectively means that the chances for successful collisions between sodium thiosulphate and hydrochloric acid will be reduced, therefore increasing the overall time for the reaction to take place. The decreasing concentration of sodium thiosulphate will slow the rate of reaction. I also think that by halving the concentration the time will double. If the concentration is halved then there are half the particles of sodium thiosulphate. This should mean that it will take double the time for the collisions to take place. Making a Fair Experiment In this experiment there are a number of things that will need to be controlled: o Temperature o Volume o The cross o Light intensity It is vital that the volume of hydrochloric acid is kept at 5 cubic cm and the sodium thiosulphate solution is kept at 50 cubic cm. ...read more.


This would give the chance for any anomalies to be identified. The gathered results were then placed into the following table. The table shows the rate of reaction (1/seconds), as well as concentration of sodium thiosulphate and time. The concentration was recorded to two decimal places, the time was recorder to two significant places and the rate of reaction which is recorded to five decimal places. Analysing and considering evidence With use of my results I was able to create two graphs or each experiment in order to see if there was any correlation between concentration and rate of reaction. By looking at the graphs I can see that when the concentration of the sodium thiosulphate is decreased the rate of reaction also decreased. This means that there is a positive correlation between concentration and rate of reaction. With use of scientific knowledge this can be explained. With a lower concentration of sodium thiosulphate there were less particles of that kind. ...read more.


Looking at my graphs there do not appear to be any anomalous results because they all follow the trend well and fit into the pattern. However I feel that as I lowered the concentration and the time increased the results became more varied. This can be shown in the way that there was a percentage difference in my two results bigger than 10%. Although I feel that this could have been caused by human error when deciding when the cross had totally disappeared. My method of carrying out my experiment was fairly accurate. I made sure that I washed the beakers clean for each reaction I had and I measured the same amount of solution in each time. Although I think there is a human error factor involved when you are measuring liquids and also looking for an end point in the reaction. I feel that this could have been overcome by of using a light beam instead of a cross. When the light intensity drops below a certain level this could signify the end of the reaction and the timer stopped. ...read more.

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