8. For each of the following situations, predict whether the experimentally determined concentration of an unknown...

8.

For each of the following situations, predict whether the experimentally determined

concentration of an unknown solution would be greater than, less than, or unchanged from the

theoretical value. Explain your reasoning in each case.

a.

The spectrophotometer is not zeroed, so all absorbance readings (for known and

unknown solutions) are 0.010 too high.

b.

The spectrophotometer is not zeroed in preparing a calibration curve, so that all

absorbance readings for the knowns are 0.010 too high. However, the instrument is

zeroed before measuring the unknown, so that its absorbance reading is correct.

Expert Solution

a) Since we are using Beer Lamberts law for finding the unknown concentration, if the any increase in absorbance will results in reporting a greater value of concentration than actual value.

Note: absorbance is drectionaly protional to concentration

b). Will be lower than the actual theoretical value. In this case unknown is found from the calibration curve. if the unknown measurement without zeroing the instrument would have given a correct result since the error is constant everywhere. In the present case we have zeroed it only for unknown which will give a less value for the concentration from the calibration curve.

queen_honey_blossom answered 2 years ago

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