11. One of the standard indicators for iodimetric titration is starch. Starch fo

Question

11. One of the standard indicators for iodimetric titration is starch. Starch forms a dark blue complex with iodine (I2) that can be measured spectrophotometrically to quantify the concentration of I2 in a solution. A student reacts an aqueous solution of unknown I2 concentration with starch, and then takes 15.00 mL of this solution and dilutes that portion with water to a total volume of 250.0 mL. The student then places an aliquot of this diluted solution inside a cuvette for analysis. The absorbance of the solution at its maximally absorbing wavelength is 0.582. The equation from the calibration curve of known concentrations is y = (2.40 x104) x + 0.016. What is the concentration of the I2 in the original solution?

a. 2.36 x 10-5 M

b. 3.93 x 10-4 M

c. 2.43 x 10-5 M

d. 4.04 x 10-4 M

e. Not enough information is provided.

Explanation / Answer

The concentration of iodine in the original solution would be,

d. 4.04 x 10^-4 M

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