Potassium ferricyanide has an extinction coefficient of 1020 1/M*cm at 420 nm. The absorbance of a sample of unknown concentration at 420 nm is 0.4268. If the path length is 10 mm, determine the concentration of the sample

Convert the path length to cm. Plug in Beer's law equation and solve for c.

A = ε l c

http://www.chm.davidson.edu/vce/spectrophotometry/beerslaw.html

To determine the concentration of the sample, we can use the Beer-Lambert law:

A = εcl

Where:
A is the absorbance
ε is the molar absorptivity/extinction coefficient
c is the concentration
l is the path length

Given values:
A = 0.4268
ε = 1020 1/M*cm
l = 10 mm = 1 cm

Substituting the given values into the equation:

0.4268 = (1020 1/M*cm) * c * (1 cm)

Simplifying the equation:

c = 0.4268 / (1020 1/M*cm)

Using the calculator:

c ≈ 4.18 x 10^-4 M

Therefore, the concentration of the sample is approximately 4.18 x 10^-4 M.

To determine the concentration of the sample, we can use the Beer-Lambert Law, which relates the absorbance of a sample to its concentration.

The Beer-Lambert Law is given by the equation:
A = ε * c * l

Where:
A is the absorbance
ε is the molar absorptivity/extinction coefficient
c is the concentration of the sample
l is the path length

In this case, we are given:
A = 0.4268
ε = 1020 1/M*cm
l = 10 mm (which we convert to cm by dividing by 10, so l = 1 cm)

Rearranging the equation, we can solve for the concentration (c):
c = A / (ε * l)

Plugging in the given values:
c = 0.4268 / (1020 1/M*cm * 1 cm)

Calculating the concentration:
c = 0.4268 / (1020)
c ≈ 0.0004178 M

Therefore, the concentration of the sample is approximately 0.0004178 M.