Question

The complex FeSCN^+2 has a molar absorptivity of 7.00 times 10^3 L/(mol.cm) at a wavelength of 580 nm. The percent transmittance of an unknown solution was measured to be 65.9% in a 1.00 cm cell. What was the concentration of the unknown solution?

Answer 1

Molar absorptivity, $\varepsilon$ = 7.0x10³ L/(mol.cm)

Percent transmmittance = 65.9 %

Path length = 1 cm

We have:

Absorbance, A = 2 - log (%T)

= 2 - log (65.9)

= 2 - 1.818

= 0.182

From Beer's law:

A = c*$\varepsilon$*l

0.182 = c * 7.0x10³ * 1

c = 0.026x10^-3

c = 2.6x10^-5 Mol/L

Hence, concentration = 2.6x10^-5 Mol/L