(Na S O (aq) + 2HCL (aq)> 2 Na Cl (aq) + H O (l) + S (s) + SO (g)
The equipment I need to carry out the work and to obtain my results is:
· Sodium thiosulphate solution
· Hydrochloric acid
· 250cm conical flask
· -5 C -110 C thermometer
· 10cm /50cm measuring cylinder
· 5 Water baths (20C, 30C, 40C, 50C, 60C)
· Stop clock
· Piece of paper with cross on
Firstly, I drew a black cross on a piece of paper, and then I measured 50cm sodium thiosulphate solution using the conical flask. The appropriate temperature was checked using the thermometer. It was at this point where I carried out the various temperatures.
At the appropriate temperature, 5cm hydrochloric acid was measured using the measuring cylinders and then added to the flask containing the sodium thiosulphate. I now placed the flask over the paper, which had a black cross on it that I had drawn earlier.
The stop clock was started immediately to make results more accurate and the time in seconds for the cross to disappear was recorded in a table like the one below. I did this at 20C-60C.
I repeated each temperature a total of 3 times to make my results accurate and calculated an average by which I compared each temperature with greater ease.
FAIR TEST: To make this a fair experiment I had to look at a lot of different factors. Firstly, I am using water baths to heat the water up instead of using a Bunsen burner. I am doing this because in a water bath when the solution gets to the right temperature it stays there, but when heated on a Bunsen burner it can go over its temperature.
Secondly, I will not stir the solution when the reaction is taking place. This is because this could speed up the reaction time so I wouldn’t have fair results.
I will also do the experiment 3 times at each temperature and then take an average so that I get a fair lot of results.
RESULTS:
CONCLUSION: From my results, I have come to the conclusion that if the temperature of a solution is raised, so is the time for the reaction to occur. The cross-disappeared more rapidly as the temperature rose and I think this was due to the increase of energy between the particles and an increase in energy between collisions that successfully passed the energy barrier.
At the lower temperatures, the time for the cross to disappear was less because the particles did not have as much energy as they did at the higher temperatures. At these temperatures the particles are colliding with much more energy and thus the reaction was much quicker and so the cross-disappeared faster.
Looking back at my prediction I conclude that my hypothesis was correct. I have shown this with my results table, my Attempts graph and my Averages graph. My line of best fit on the averages graph shows that as you increase the temperature the rate of reaction is sped up. The only problem with my graph is that it has a set of anomalies on it, but apart from that they all support my prediction.
Evaluation: I think that this experiment has gone very well for me. My results were of a particularly accurate standard as I did each the experiment 3 time at each temperature and then calculated an average from these times. There were only one set of anomalies within my results table and I think that this was because of a fault with the water bath as it only happened on this temperature and if I was to do this investigation again I would check that all the equipment was in working order.
I think that I could have repeated my results more because although the experiment was repeated 3 times, I believe I could of got the most accurate results by repeating them more. But in the time given I could not have done this so I would have to say that, with more time, I would repeat the results further for even more accurate and reliable results.
I believe that I could have improved the method by making it more specific. I stated clearly what I was going to do during the investigation but I believe I could have gone into greater depth and used more scientific words to show what I was going to do.
I believe that I did get a suitable range of results for this experiment. I recorded results from temperatures that ranged from 20 C to 60 C; I think that this is a very good range to see how temperature affects the rate of reaction. But, I feel that I could have tested it at higher temperature as stopping testing at 60 C reduces the chance of knowing if anything changes if the temperature reaches a certain point. The only problem with doing this is that maybe at a certain the experiment would get violent so I don’t know if it would help with my results.
Some other points in the experiment that I feel I could have improved on were factors like controlling the stopwatch and measuring the amount of sodium thiosulphate and hydrochloric acid. There is lots of points were human error could happen. However I felt I paid close attention to all these points during the experiment.
Overall, this investigation has been a very successful one. I feel my results and analysis have been as accurate and reliable as they could have been under the time given. However I feel with extra time, I could have repeated the experiment and made it even more accurate and adapted it to try other variables i.e. concentration or adding a catalyst. I could have also compared my investigation to another investigation that looks at how temperature affects the rate of reaction such as mixing Marble chips and Hydrochloric Acid or Magnesium ribbon and Hydrochloric Acid, I think that if I had done this then it would have shown if my investigation went well compared to others. These are the ways that I could expand on the original question.
