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Factors affecting the rate of reaction of Hydrochloric acid with sodium thiosulphate

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Introduction

Rate of Reaction investigation: Factors affecting the rate of reaction of Hydrochloric acid with sodium thiosulphate When hydrochloric acid and sodium thiosulphate react, they form sulphur, sulphur dioxide and water as products. This can be expressed in the equation: Hydrochloric + Sodium -> Sodium + Sulphur + Sulphur + Water Acid Thiosulphate Chloride Dioxide HCl (aq) + Na S O (aq) -> NaCl (aq)+ S (s) + SO (g) + H O (l) In this experiment, I will investigate how changing the concentration of one of the reactants affects the rate of the reaction. Prediction I predict that as the concentration of the sodium thiosulphate becomes more diluted the rate of reaction will become slower as there is less sodium thiosulphate and more water in the beaker for the acid to react with. This will take the reaction longer to take place and so the rate of reaction decreases. This can be explained more clearly by relating to the collision theory. If solutions of reacting particles are made more concentrated there are more particles per unit volume, so therefore collisions between reacting particles are more likely to occur. ...read more.

Middle

I waited for the visibility of the black cross to be completely obscured by the mixture, stopping the clock when this happened. I then recorded the time and washed out the conical flask before starting the next experiment. Analysis My results tables and graphs display my findings from this experiment. he first graph plots time taken for the reaction to take place against the concentration of sodium thiosulphate. It has negative correlation, as the time taken for the reaction to take place increases as the concentration becomes more diluted. The highest concentration completes the reaction in 30 seconds, whereas the lowest concentration, 0.1 mols sodium thiosulphate, takes around 600 seconds to complete. The lowest concentration takes around 20 times longer to react than the highest concentration. The line of best fit is a curve because the decrease in time is not proportional as the concentration is diluted. Graph 2 for experiment 2 shows a similar pattern to the graph for experiment 1. Point 0.6 appears to be anomalous, which is most likely to be due to errors in the timing of the experiment. The rate of reaction increases more or less in proportion to the concentration. ...read more.

Conclusion

to assume that after a thorough washing out, the glass would be clean and would not contaminate my next experiment, but this still could have occurred. The only thing I can suggest to improve this fault would be to use a fresh, clean conical glass for each experiment, but by using different equipment this may also cause an inaccuracy in my findings. The use of a pH meter to monitor the pH of the solution as it is reacting may have helped my experiment by enabling me to see the reaction take place more clearly. To provide more evidence for my investigation I could use a thermometer to measure the temperature of the solution during the experiment to see if any heat is given off and how this may affect the experiment. For further investigation, I could use stronger sodium thiosulphate to see if there is a limit to how quickly the reaction can take place. Overall, my results and graphs clearly show the relationship between the effect of concentration upon the rate of reaction, so I do not think that the faults in my method have caused any major problems, however, with the suggested improvements I could achieve more accurate and reliable results to support my conclusion further. ...read more.

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