Question

Calculate the molar concentration of a solution that has a measured absorbance of 0.635 using a 1-cm pathlength cuvette and an extinction coefficient of 46,000.0 M^-1cm^-1.

Answer 1

Molar concentration from absorbance

To solve this problem, we use Beer's Law:

A= lc

where

A= the absorbance
ε= the molar absorptivity constant
l= the path length
c= the molar concentration of the solution.

We can rearrange this equation to get

c=A/εl

A=absorbance = 0.635

l= the path length = 1 cm

= extinction coefficient = 46,000.0 M^-1 cm^-1 = 46,000.0 L mol ^-1 cm^-1

c= 0.635/ 46000 1 = 1.3810^-5 mol L^-1 = 1.3810^-5 M

1.3810-5 mol L-1 = 1.3810-5 M