7. Measurement errors might be random or systematic (Silberberg 6th p. 29). Refe

Question

7. Measurement errors might be random or systematic (Silberberg 6th p. 29). Refer to the equilibrium for reaction 1. A likely error systematic error in this experiment is overshooting the endpoint of your titration of the aqueous layer, or the endpoint of the mineral oil layer (ie adding too much thiosulfate). In answering this question, you must justify your reasoning by reference to the appropriate equations. (a) Explain how overshooting the titration of the aqueous layer Ge. using too large a value for the volume of thiosulfate to react with the 12 and of 13 would affect the concentrations of [I (aq)], [I20aq)], [I3-(aq)] and therefore of the calculated K. 2 marks)

Explanation / Answer

7. Systematic and random error

(a) Overshooting thiosulfate would give a higher value for I3- reacted and thus higher amount of I- started in the reaction. The resultant K would also be higher than the actual value.

(b) If the minimum volume of thoiosulfate used is higher, the resultant volume would be lower and thus gth amount of I3- reacted calcuated would be lower and I- will be lower than actual value.

(c) Adding thiosulfate to the aqueous layer would give the desired K value in the titration experiment.

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