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To Investigate the Effect of Changing the Concentration On the Rate of Reaction In Two Experiments

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Simon Shepherd 13th February Chemistry Rates of Reaction Practical Coursework Planning Experiment 1 Aim: to investigate the effect of changing the concentration on the rate of reaction in two experiments - sodium thiosulphate and hydrochloric acid, and magnesium and hydrochloric acid. Method: a cross will be drawn on a piece of filter paper and placed underneath a conical flask. The substances required - sodium thiosulphate, hydrochloric acid and water will be measured out. The water will be used to dilute and therefore vary the concentration of the sodium thiosulphate. 5ml will always be measured out of hydrochloric acid as a constant with a 10ml measuring cylinder. The water and sodium thiosulphate will always total to 50ml and will be measured with a measuring cylinder of the same value. The sodium thiosulphate solution will be added first, and as soon as the hydrochloric acid is poured into the conical flask the timer will be started. The reaction will then take place, and the solution will turn cloudy over a period of time. When the cross on the filter paper has been completely obscured, the timer will be stopped and the time taken recorded. The rate can then be calculated by dividing 1 by this value. ...read more.


It must be also kept away from other substances in the laboratory as it reacts violently and dangerously with many of them. Again, skin contact with hydrochloric acid must be avoided as it is corrosive. List of Apparatus: * 250ml conical flask for reaction to take place in, as it is the same as used in the first experiment so they can be compared with greater accuracy. * Digital stop clock accurate to half a second as it is easier to read than an analog clock and no more accuracy than this is required. * Two 50ml measuring cylinders to measure the water and hydrochloric acid as the range of their volumes varies from 0-50ml so this is the most accurate measuring cylinder that could be used. Preliminary Results: the following preliminary results were obtained. This range of readings clearly gives enough variation to make it easy to determine what type of relationship occurs between concentration and rate on my graph. Number of Readings: 8 readings will be taken spread evenly over the range above to allow for the correct type of graph to be determined. Also, each reading will be taken twice to detect any errors, if they occur. ...read more.


Improvements to the experiment There can be improvements to the experiment so that my results are to the point nearest to perfect these are: - 1. I would have a computer take the readings for me so that they are more accurate than the other results that I got as the computer is very precise. 2. I would use distilled water so that my experiment can not be altered by that impurity. 3. Then there is the impurity of the magnesium as it forms a protective layer so I would use a vacuum so that no oxygen would oxidise the magnesium. 4. As we had two different sources of the HCL I would keep them from the same jar. 5. I would use a water bath. 6. I would take more results to get abetter graph. 7. I could have a greater degree of accuracy. I could have used a greater degree of accuracy as this may have altered my results as the timer may be to 1/2 a second so we could make it to 1000th of a second so that we get better reading also the measuring cylinders may have not been used correctly so giving the wrong volumes. I could go on to do further work in the area different acid so sulphuric acid or nitric acid or I could use a different base for example potassium or sodium. ...read more.

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