The dye molecule 7-aminocoumarin has an extinction coefficient of 2800M-1cm-1 at 432nm. An aqueous sample of 7-aminocoumarin is placed in a cuvette with a 1.00cm path length and the absorbance is found to be 1.75 at 432nm. What is the molarity of 7-aminocoumarin in this sample?
The extinction coefficient is the slope of the line, and will not change ever at 432nm. This is just plug and chug.
A=ebc
A=1.75
e=2800M-1cm-1
b=1.00cm
c=?
solve for c,
A/be=c
To find the molarity of the 7-aminocoumarin sample, we can use the Beer-Lambert Law, which relates the absorbance (A) of a solution to the concentration (c) of the absorbing species and the path length (l) of the cuvette.
The Beer-Lambert Law equation is given as:
A = εcl
Where:
A = Absorbance
ε = Extinction coefficient
c = Concentration
l = Path length
In this case, we are given the following information:
Extinction coefficient (ε) = 2800 M^-1 cm^-1
Path length (l) = 1.00 cm
Absorbance (A) = 1.75
Now, we can rearrange the equation to solve for the concentration (c):
c = A / (εl)
Substituting the given values:
c = 1.75 / (2800 M^-1 cm^-1 * 1.00 cm)
By calculating this, the final concentration of 7-aminocoumarin in the sample would be:
c = 6.25 x 10^-4 M