I have this question in chemistry kinetics, and there is a graph showing concentration of hydrogen peroxide and average rate of reaction. As the concentration decreases, so does the rate of reaction. There are two possible anomalies on the graph, if one is removed then the graph resembles a curve, and if the other is removed then it is a line .
4)other than repeating a measurement, suggest how else the student could confirm which of the two lines of best fit is the true relationship
5) Suggest the most likely cause of an anomalous result on a graph
Chemistry AS level kinetics graph question Watch
- Thread Starter
- 04-01-2017 14:53
- Official TSR Representative
- 06-01-2017 16:23
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Just quoting in Danny Dorito so she can move the thread if neededSpoiler:Show(Original post by Danny Dorito)
- 08-01-2017 09:39
I think the thread is indeed in the right place (does defo sound like an A level Chemistry Q - I think it's just a very difficult and thought-provoking Q - maybe that is the reason for no replies) - Hi imaan567, I will try and have a shot at the answer to this, but it is only through conjecture and speculation rather than defo knowing the answer - hope it helps.
Firstly "suggest" Qs at A level (I only know for sure in my specialist subject (biology), but probs applies to other sciences too), suggest Qs have a wider scope in the mark scheme, simply out of the meaning of the word "suggest", so if you put down almost anything that makes sense AND give a valid explanation (explain means "Why") of your answer, you will score (a) mark(s).
4) If removing the first anomalous result produces a curve that is concave downwards, i. e. rises steeply and flattens out at high concentrations, then from our knowlege of the effect of concentration on rate of enzymaic reaction, this is likely to be correct because one would expect that as the hydrogen peroxide conc-n decreases (as it is used up in the reaction), the number of active sites of enzyme binding H2O2 will drop until Conc-n of H2O2 becomes nearly zero.
If removing the second anomalous result, produces a line (straight line, presumably - ambiguous Q - is this Edexcel lol?), then try and work out the limiting factor (sorry, tall order, but stupid Q stupid A!! )); if the limiting factor is the concentration, then the maximum rate of reaction is likely to be (in absolute terms) quite low, i.e. to put it very empirically, this "line" will stop at a very modest concentration (x axis value) - in other words, it will be quite short, depending on the scales used for the x and y axes. f this is the case (short line), chances are the first one (curve) is once again the correct one.
5) Measurement error (perhaps the units mixed up) OR a confounding factor (means not a "fair test" as they teach it these days in baby language [sorry!]!).
Sorry, this might sound a little convoluted, but I can't think of anything more obvious!
Mukeh (Specialist Biiolgy tutor)