Question

If a solution of acetonitrile in water whose concentration is 1 x 10^-4 mol/dm³ is examined at a wavelength of 224nm, the absorbance is determining to be 30. What's is the molar absorptivity of the absorption band? Assuming the length of the cuvette is 1cm.

Answer 1

Given, concentration of solution = 1 x 10^-4 mol/dm³

absorbance = A = 30

length of cuvette = 1cm

as we know

absorbance A = log\(\frac{I_0}{I}\) = εbc

where

b = length of cuvette

c = concentration of solution

ε = molar absorptivity

A = absorbance

∴ 30 = ε x 1 cm x 1.0 x 10^-4 mol/dm³

ε = \(\frac{30}{1\ cm\times\ 1.0\times\ 10^{-4}mol/dm^3}\)

ε = 30 x 10⁴ L mol^-1cm^-1

or ε = 3.0 x 10⁵ Lmol^-1cm^-1

Hence, the molar absorptivity (ε) will be 3.0 x 10⁵ Lmol^-1cm^-1

While the reduction potential of fe (iron) is less than H⁺ but greater than H₂0 because at that iron does not corrode in alkaline.