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The determining of a rate equation from the reaction of sodium thiosulphate with hydrochloric acid - page 7
Keywords: The determining of a rate equation from the reaction of sodium thiosulphate with hydrochloric acid
By Carlitob10 on 04/11/2006 11:57:07
Level: A Level (Year 13)
Page Number: 7 of 8 pages: 1 2 3 4 5 6 7 8ensure that the reagents are properly homogenised for the reaction to occur. It is difficult, therefore, to do all these things simultaneously.
• For each run of the experiment, I ensured that the amounts of reagents were diluted within a certain range, so that the speed of reaction was not too fast. In this way, I minimised the possibility of gross error, in as much as none of my reactions were to fast to follow properly, and any errors in timing the reaction would be lessened over the longer time period.
• Looking for an end point in the reaction can be very subjective. Although this reaction had a fairly definite end point, it would still be difficult to provide a universally applicable definition of “obscured” for the disappearing cross. However, the following could be done to standardise this aspect of the experiment:
• A light could be attached to a stand and clamp and then connected to a sensor, which would receive a signal from the light to stop the clock when the solution was cloudy enough to make the cross disappear. This set-up would give me a more accurate reading of the end point of the reaction than simple observation. A diagram of this apparatus is shown below.
• One set of measurements alone is not usually very reliable. In order to obtain reliable results, it is necessary to carry out the investigation more than once. Obviously, the more replicates, the more reliable my results will be. This however, has to be balanced against the time constraints of repeating the procedure numerous times. I only had time to take one 3 sets of measurements. It was opportune, therefore, that my results contained no glaring anomalies. This was borne out by the resulting graphs of concentration of reagents against rate of reaction. If I had had more time, however, I would have liked to have replicated the experiment at least twice more, and then averaged out the results, in order to minimise random errors and impart more credibility to them.
• I could have conducted some preliminary analysis, such as eyeball-fitting a line on the graph, in my notes while I was doing the experiment. In this way, I would have been able to notice whether something was amiss right away, rather than after I had completed the whole experiment.
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