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10. (5) An old method for the analysis of Cu2+ ion in a solution sample was to t

ID: 576144 • Letter: 1

Question

10. (5) An old method for the analysis of Cu2+ ion in a solution sample was to treat the sample with KI, which results in the following reaction: 2 Cu2+(aq) + 41(aq) 2 Cul(s) + 12(aq). The amount of I2 generated can be determined by titration, and from this the amount of copper in the solution sample can be calculated. Suppose that the solution sample also contains some Fe, o react with lion, producing 12: 2 Fe3"(aq) + 2 1(aq) 2 Fe2+(aq) +12(aq). Explain what effect this would have on the measurement of the amount of I2 formed, and on the measurement of the amount of copper in a sample. Explain whether this type of error would be random or systematic.

Explanation / Answer

The measured value of amount of iodine formed will be higher than actual value. It will also include iodine obtained from reaction with ferric ions.

The measured value of amount of copper in sample will be higher than actual value. It will also include amount of iron.

This type of error is systemic error.