Question

There is a substance in a solution (0.03 mole/liter). The length of cuvette is 2 cm and only 10% of the certain light beam is transmitted. What is the extinction coefficient of the substance

Answer 1

The molar absorptivity coefficient is,
`16.67 M^(-1)cm^(-1)`.

Step-by-step explanation:

Using Beer-Lambert's law :

Formula used :

`A=\epsilon * C* l`

`A=\log (I_o)/(I)`

`\log (I_o)/(I)=\epsilon * C* l`

where,

A = absorbance of solution

C = concentration of solution =
`0.03 mol/L=0.03 M`

l = path length = 2 cm

`I_o` = incident light

`I` = transmitted light

`\epsilon` = molar absorptivity coefficient = ?

A compound absorb 90 % of the light and transmit 10% of light.

Transmittance = 10% = 0.1

`0.1=(I)/(I_o)`

`A=\log (I_o)/(I)=\log (1)/(0.1)=1`

Now put all the given values in the above formula, we get the molar absorptivity coefficient.

`1=\epsilon * (0.03 M)* ( 2 cm)`

`\epsilon=16.67 M^(-1)cm^(-1)`

Therefore, the molar absorptivity coefficient is,
`16.67 M^(-1)cm^(-1)`.