Keenan is interested in the concentration of blue dye in his favorite beverage.

Question

Keenan is interested in the concentration of blue dye in his favorite beverage. He knows that spectroscopy can be used to determine the concentration of dye molecules in a solution. After making several solutions of known concentration, Keenan measured the absorbance of each of the solutions and prepared the following calibration curve. Keenan then finds that if 20.0 mL of his favorite beverage is diluted to a volume of 100.0 mL, the diluted solution has an absorbance of 0.730. Determine the concentration of blue dye in the undiluted beverage.

Explanation / Answer

Recall beer's law

A = e*l*c

A = absorption

e is the molar absorbtivity with units of L mol-1 cm-1

l = lenght of path in cm

C = Molar concentration

so...

Voriginal = 20 mL

Vdilution = 100 mL

Adilution = 0.73

Determine the blue dye in undiluted beverage

so..

from the graph

A = slope*M

slope = e*l = 68663

A = 68663*M

substitute for diluted species

0.73 = 68663*M

M = 0.73/68663 = 0.00001063163 M

this is in the diluted case

so

Moriginal * Voriginal = Mdiluted * Vdiluted

Moriginal = 0.00001063163*100/20

Moriginal = 0.00005315815 M

Related Questions

Navigate

• Browse (All)
• Browse K
• Subjects

---

---

Integrity-first tutoring: explanations and feedback only — we do not complete graded work. Learn more.