Question

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?

Answer 1

Answer:

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