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# Investigating the rate of reaction between Sodium Thiosulphate and Hydrochloric Acid

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Introduction

Investigating the rate of reaction between Sodium Thiosulphate and Hydrochloric Acid My aim is to answer the question 'How can I make this reaction go faster?' Equation: (Taken from 'Chemistry' by J.A.Hunt and A.Sykes): 2HCl(aq)+Na2S2O3(aq) 2NaCl(aq)+SO2(g)+S(s)+H2O(l) Preliminary Results Volume of Na2S2O3 (cm�) Added to...(cm�) Time taken for reaction (seconds) 50 10 HCl and 0 H2O 30 15 10 HCl and 35 H2O 139 10 10 HCl and 40 H2O 256 5 10 HCl and 45 H2O 315 With my results, I have found that a volume of 5cm� was too little and so took too long. I will leave this result out and add 20cm� and 35cm� to enable me to have a wide range of results. Prediction: My predictions come from the above preliminary results. Generally, as concentration is increased by a factor of 10, the reaction time decreases by 285 seconds?reaction rate � 10 times faster. Also, from the above results, when the concentration is doubled, time decreases by roughly a minute? for every 5cm� of Sodium Thiosulphate added (and 5cm� of H2O taken away) reaction� 1 minute faster. This is due to the Particle Theory. The higher the concentration of Sodium Thiosulphate, the more particles there are in the solution, which also means there are more particles for the Hydrochloric Acid particles to collide with, creating more energy thus a faster reaction. ...read more.

Middle

Method: 1. Measure 50cm�of Na2S2O3 and 10cm� HCl and pour them into separate beakers, making sure you take note of which chemical is which (as both are colourless!) 2. Place the conical flask onto the black cross so that you can see it through the base of the flask. Set up the timer and pour the two chemicals into the conical flask. Start the timer immediately. 3. Keep an eye on the black cross through the top of the conical flask. When you can no longer see the cross through the solution, stop the timer. 4. Record the results and repeat with other concentrations of Na2S2O3. (Make sure concentrations are accurate and always of an equal volume) 5. Between each test, make sure all apparatus is clean to minimise cross-contamination and achieve better and more accurate results. Results: Volume Na2S2O3 (cm�) Time 1 (seconds) Time 2 (seconds) Time 3 (seconds) Average time (seconds) 50 32 32 37 34 35 64 65 60 63 20 87 90 88 88 15 211 195 213 206 10 256 287 314 286 Analysis: This graph shows my results, i.e. Time against concentration. It shows that there is s definite curve in the results, as expected for this experiment. ...read more.

Conclusion

It later occurred to me that I had done the test at a different time of day to the other results, resulting in a different temperature. This, as I remembered from previous lessons on how reaction rates are increased, would have affected my results, so the new results were done at roughly the same time of day, and therefore temperature. I also made a mistake in calculating the reaction rates of the sulphur as I mis-typed the result into my calculator and got a completely anomalous result. This was rectified as soon as I noticed the error. As I have already said, temperature may affect the results and make them faster/slower depending on the temperature the chemicals are stored at and the room temperature and finally, I believe that my investigation has proved that concentration has an affect on the results as well. Using a measuring meant that my solutions were not as accurate as they could have been, e.g. when calculating 5cm� volume in my preliminary results, the 10cm� cylinder would have an error of 0.1cm� each way, calculating as 20% difference, as seen in the formula below: % Error= 0.1 x100 5.0 Using a Burette would have meant that my solutions would have been more accurate than they were. ?? ?? ?? ?? Simon Garlinge 10 CH 10:1 Chemistry Coursework 1 ...read more.

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