an 80ppm of KMno4 produced an absorbance of 0.4 in a 1.0cm cuvette. Calculate the molar absorptivity of KMno4
A = ebc
You have A.
You want e.
You have b.
Convert 80 ppm to mols/L and substitute; solove for e.
(Note: Remember that 1 ppm = 1 mg/L; therefore, 80 ppm is 80 mg/L. That should make it easy to convert to mols/L KMnO4)
To calculate the molar absorptivity (ε) of KMnO4, you can use the Beer-Lambert Law, which relates the absorbance (A), molar absorptivity (ε), concentration (c), and path length (b) of the solution.
The Beer-Lambert Law is expressed as:
A = ε * c * b
In this case, you have the absorbance (A) and the path length (b) is 1.0 cm. You are given that the concentration (c) is 80 ppm or 80 mg/L.
To calculate the molar absorptivity (ε), rearrange the equation:
ε = A / (c * b)
Substituting the values:
ε = 0.4 / (80 mg/L * 1.0 cm)
To simplify the units, convert mg/L to M (moles per liter) by using the molar mass of KMnO4, which is 158.034 g/mol.
ε = 0.4 / (80 mg/L * 0.001 L/mL * 1 mol/158.034 g * 1000 g/kg)
Doing the calculations:
ε ≈ 0.253 L/(mol * cm)
Therefore, the molar absorptivity (ε) of KMnO4 is approximately 0.253 L/(mol * cm).
To calculate the molar absorptivity (ε) of KMnO4, you can use the Beer-Lambert Law equation:
A = ε * l * c
where:
A = Absorbance
ε = Molar absorptivity
l = Path length (in this case, it is 1.0 cm)
c = Concentration of the KMnO4 solution in moles per liter (M).
From the given values, the absorbance (A) is 0.4, the path length (l) is 1.0 cm, and the concentration (c) is 80 ppm or 80 mg/L. However, we need to convert the concentration from ppm to M.
To convert ppm to M, you need to know the molecular weight of KMnO4. The molecular weight of KMnO4 is:
K (rate) = 39.10 g/mol
Mn (manganese) = 54.94 g/mol
O (oxygen) = 16.00 g/mol (four atoms)
Total molecular weight of KMnO4 = 39.10 + 54.94 + (16.00 × 4) = 158.04 g/mol
Now, let's convert 80 ppm to M:
80 ppm = 80 mg/L = 0.080 g/L
To convert this to moles per liter (M), divide the mass by the molecular weight:
Concentration (c) = 0.080 g/L / 158.04 g/mol
Now, we can substitute the values in the Beer-Lambert Law equation:
0.4 = ε * (1.0 cm) * (0.080 g/L / 158.04 g/mol)
Simplifying the equation:
0.4 = ε * (0.080 / 158.04)
Now, solve for ε:
ε = 0.4 / (0.080 / 158.04)
Calculating the molar absorptivity (ε):
ε ≈ 2.52 L/(mol·cm)
Therefore, the molar absorptivity of KMnO4 is approximately 2.52 L/(mol·cm).