Question

There is a substance in a solution (8g/liter). The length of a cuvette is 1cm and only 25% of the certain light beam is transmitted. What is the absorption coefficient?

Answer 1

We have , Absorbance = log ( I ₀ / I )

Where , I ₀ intensity of incident light and I intensity of transmitted light.

We have, I ₀ =100 % and I = 25 % .

Therefore, A = log (100 /25 ) = 0.602

From Beer's law , we have relation A = $\epsilon$ b C

Where A is absorbance, $\epsilon$ is absorption coefficient , b is path length and C is concentration of substance.

$\therefore$ 0.602 = $\epsilon$$\times$ 1 cm $\times$ 8 g / L

$\epsilon$ = 0.602 / 1 cm $\times$ 8 g / L = 0.075 g L ^-1 cm ^-1

ANSWER : absorption coefficient of substance = 0.075 g L ^-1 cm ^-1