Question

The concentration of Fe2 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 0.242 . The reagent blank in the same cuvette has an absorbance of 0.041. What would be the absorbance reading for each of these two solutions if measured in a 5.00 cm cuvette

Answer 1

• Absorbance of sample solution = 1.21

• Absorbance of reagent blank = 0.205

Step-by-step explanation:

In order to solve this problem we need to keep in mind the Lambert-Beer law, which states:

• A = ε*b*C

Where ε is the molar absorption coefficient, b is the length of the cuvette, and C is the concentration.

By looking at the equation above we can see that if ε and C are constant; and b is 5 times higher (5.00 cm vs 1.00 cm) then the absorbance will be 5 times higher as well:

• Absorbance of sample solution = 0.242 * 5 = 1.21

• Absorbance of reagent blank = 0.041 * 5 = 0.205