1. A solution that contains 50 mg of a colored compound dissolved in 100 mL of a
ID: 628288 • Letter: 1
Question
1. A solution that contains 50 mg of a colored compound dissolved in 100 mL of a solvent absorbs half of the incident light at 500 nm when an aliquot is placed in a cuvette that has a path length of 1 cm. (a) Determine what optical path length for the measurement beam would result in absorption of 75% of the incident light. (b) What mass of the compound will have an absorbance of 1.5 when measured in a 1-cm cuvette when dissolved in 1 liter of solvent? (c) What concentration (mg/mL) transmits 90% of the incident light in a 1-mm cuvette?Explanation / Answer
Given,
l = 1 cm
c = 50/100 = 0.5 mg/mL
A =
= -log(0.50) = 0.30103
e = A/cl
= 0.30103/(0.5 x 1)
= 0.60206 ml/mg.cm
(a)
t = = 0.25
A = -log(0.25)
= 0.60206
l = A/ec
= 0.60206/(0.60206 x 0.5)
= 2 cm
(b)
c = A/el
= 1.5/(0.60206 x 1)
= 2.4914 mg/mL
Mass = vc
= 1000 x 2.49143
= 2491.43 mg
(c)t = 0.90
A = -log(0.90)
= 0.0457575
= 0.1 cm
c = A/el
= 0.0457575/(0.60206 x 0.1)
= 0.76 mg/mL
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