You are measuring the concentration of Fe 2 in a sample is determined by measuring the absorbance of its complex with ferroxine. The sample, measured in a 1.00 cm cuvette, has an absorbance of 0.333. The reagent blank in the same cuvette has an absorbance of 0.014. What would be the absorbance reading for each of these two solutions if measured in a 5.00 cm cuvette?

Question

Chemistry

Kiera Brady

13 May, 12:05

You are measuring the concentration of Fe 2 in a sample is determined by measuring the absorbance of its complex with ferroxine. The sample, measured in a 1.00 cm cuvette, has an absorbance of 0.333. The reagent blank in the same cuvette has an absorbance of 0.014. What would be the absorbance reading for each of these two solutions if measured in a 5.00 cm cuvette?

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Sharon · Answer 1

Sample: 1.67

Blank: 0.070

Explanation:

The absorbance of a solution (A) is explained by the Beer-Lambert law.

A = ε. l. c

where,

ε is the absorptivity of the species

l is the optical path length

c is the molar concentration of the species

As we can see, the absorbance is directly proportional to the path length, that is, the length of the cuvette. If l is increased 5 times (1.00 cm to 5.00 cm), the absorbance will also be increased 5 times.

The absorbance of the sample will be 5 * 0.333 = 1.67

The absorbance of the blank will be 5 * 0.014 = 0.070