Question

The molar absorptivity of FD&C Yellow #5 at 430 nm is $\varepsilon$ =2.43*10⁴ M^-1cm^-1. The absorbance of a sample of Gatorade Lemon-Lime at 430 nm is measured as 0.27 using a 1 cm cuvette. Assuming the path length is 1 cm, calculate the molarity of Yellow #5 in Gatorade.

Answer 1

Given molar absorptivity, E = 2.43x10⁴ M-1cm-1

Absorbance, A = 0.27

path length, l = 1 cm

Applying the relation,

Absorbance,A = ECl

where C = molarity of the solution

=> 0.27 = 2.43x10⁴ M-1cm-1 x C x 1 cm

=> C = 0.27 / (2.43x10⁴ M-1cm-1 x C x 1 cm)

=> C = 1.11x10^-5 M (answer)