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Investigating the rate of reaction between hydrochloric acid and sodium thiosulphate.

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Introduction

Investigating the rate of reaction between hydrochloric acid and sodium thiosulphate Plan: We are looking at the reaction of sodium thiosulphate with HCL acid to see the changing effect different concentrations of sodium thiosulphate have on a reaction. Equation: Sodium thiosulphate + HCL---- sodium chloride + sulphur dioxide + Sulphur + Water Na SO O ---- 2NaCl + SO + S + H O Apparatus: Stopwatch 250cm3 conical flask Paper with cross on 2 + 100cm3 measuring cylinders Stock solutions of HCL and thiosulphate. I.e. 0.03m, 0.06m, 0.09m, 0.12m, 0.15m. Safety We will be using a substance called Hydrochloric acid therefore it would be advised to wear safety goggles to prevent the acid reaching your eyes and making sure it doesn't come into contact with skin because it is corrosive. Fair Test In order for my findings to be valid the experiment must be a fair one. I will use the same standard each time for judging when the X has disappeared. I will make sure that the measuring cylinders for the HCL and thiosulphate will not be mixed up. The amount of HCL will be 25 cm3 each time, and the amount of thiosulphate will be fixed at 25 cm3. Prediction I predict that as the temperature is increased the rate of reaction will increase. I also predict that as the concentration of the sodium thiosulphate increases the rate of reaction will increase. ...read more.

Middle

5) Stop the watch when the cross has fully disappeared. 6) Repeat using 0.06m3 of sodium thiosulphate etc. 25 cm3 of HCL (0.5m) and 25 cm3 of sodium thiosulphate (at varying concentrations) are poured out into two measuring cylinders and then poured into a conical flask, which is placed on top of a board marked with letter X. The stopwatch will now be started. When the mixture has turned sufficiently cloudy so that the letter X can no longer be seen the stopwatch will be stopped and the time will be recorded. The experiment is repeated with all the concentrations. The whole procedure is then repeated. Repeat results and averages will be taken to improve the credibility of the findings, and present solid grounding for the final conclusion. The repeat results will help to solve any anomalies and the average will give a good summary of the results of the experiment. However if one set of results is entirely different to the other, a third experiment will be performed to replace the anomalous set of results. Results: Conc. Of thiosulphate Time 1 Time 2 Time 3 Average Volume of HCL and Na SO O Conc. Of HCL 0.03m 20% 8'59'06 9'03'24 9'02'37 0. 001845060 25cm3 0.5m 0.06m 40% 4'17'59 4'14'62 4'16'82 0.003906256 25cm3 0.5m 0.09m 60% 2'00'47 1'57'19 1'57'78 0.008474576 25cm3 0.5m 0.12m 80% 1'27'54 1'30'59 1'26'72 0.011764705 25cm3 0.5m 0.15m 100% 56'57 57'25 60'32 0.017544306 25cm3 0.5m Anomalous results: We did not have any anomalous results. ...read more.

Conclusion

Maybe using a burette or a pipette or even a water bath during the experiment. Further Investigation- To carry on further investigation we would have altered a number of things. We could higher the concentration of the sodium thiosulphate. The highest amount we were given was 0.15M; we could go higher and use a concentration of 1.2M etc, to see how the results would compare. We could also change the temperature by using a Bunsen burner and see what a change in temperature does to the experiment. We would do this by changing the temperature. We would add 25 cm of HCL, and 25 cm of sodium thiosulphate (at varying concentrations) into a measuring cylinder, then we would pour them out into two conical flasks. A beaker is half filled with hot water from a tap. The water is placed on top of a Bunsen on a blue flame and the two conical flasks would be placed inside the water bath. The water is heated to the necessary temperature (30�C to 70�C) then the two measuring cylinders are taken out and the contents of both are poured into a conical cylinder. The time it takes for the X to disappear is timed and recorded. The experiment is repeated using all the temperatures. The entire procedure is then repeated. In this experiment I have found that as the temperature and concentration is increased the time taken for the reaction to take place decreases. This means the rate of reaction increasers as it takes less time for a reaction to take place, so more take place per second. ...read more.

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