A 7.25 × 10-5 M solution of potassium permanganate has a transmittance of 44.1% when measuredin a 2.10 cm cell at a wavelength of 525 nm. Calculate(a) the absorbance of this solution;(b) the molar absorptivity of KMnO4
Question
A 7.25 × 10-5 M solution of potassium permanganate has a transmittance of 44.1% when measuredin a 2.10 cm cell at a wavelength of 525 nm. Calculate(a) the absorbance of this solution;(b) the molar absorptivity of KMnO4
Solution
To calculate the absorbance of the solution, we can use the formula:
Absorbance (A) = -log10(Transmittance)
Given that the transmittance is 44.1%, we can calculate the absorbance as follows:
A = -log10(0.441)
Using a calculator, we find that the absorbance is approximately 0.355.
To calculate the molar absorptivity (ε) of KMnO4, we can use the Beer-Lambert Law equation:
A = ε * c * l
Where A is the absorbance, ε is the molar absorptivity, c is the concentration of the solution in moles per liter, and l is the path length of the cell in centimeters.
We are given the concentration of the solution as 7.25 × 10-5 M and the path length as 2.10 cm. Substituting these values into the equation, we can solve for ε:
0.355 = ε * (7.25 × 10-5) * 2.10
Simplifying the equation, we find:
ε = 0.355 / [(7.25 × 10-5) * 2.10]
Using a calculator, we find that the molar absorptivity of KMnO4 is approximately 2.42 × 104 M-1 cm-1.
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