Question

A student measures the absorbance of a sample of red dye #3 using a spectrophotometer. If the absorbance is measured as 0.468, what is the concentration of red dye #3 in the sample?
Enter your answer in units of micromolar to three significant figures.

n the lab spectrophotometer, d = 1.00 cm. For Red dye #3, ε = 7.96 x 104 M-1 cm-1.

Answer 1

Answer:

5.88 μM is the concentration of red dye in the sample.

Explanation:

Absorbance is defined s capacity of a substance to absorb a light of a specified wavelength.It is calculated by using Beer-Lambert Law:

$A=\epsilon lc$

A = absorbance

$\epsilon$ = Molar absorptivity

c = concentration

l =  Length of the solution through which light passes

Given, A = 0.468, l = d = 1.00 cm,c = ?

$\epsilon =7.96\times 10^4 M^{-1} cm^{-1}$

$A=\epsilon lc$

$0.468=7.96\times 10^4 M^{-1} cm^{-1}\times 1.00 cm\times c$

$c=5.8793\times 10^{-6} mol/L=5.8793 mol/(\mu L)\approx 5.88mol/(\mu L)$

($1 L= 1,000,000 \mu L$)

5.88 μM is the concentration of red dye in the sample.