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

Answer:

The molar absorptivity coefficient is, $16.67 M^{-1}cm^{-1}$.

Explanation:

Using Beer-Lambert's law :

Formula used :

$A=\epsilon \times C\times l$

$A=\log \frac{I_o}{I}$

$\log \frac{I_o}{I}=\epsilon \times C\times l$

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

$0.1=\frac{I}{I_o}$

$A=\log \frac{I_o}{I}=\log \frac{1}{0.1}=1$

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

$1=\epsilon \times (0.03 M)\times ( 2 cm)$

$\epsilon=16.67 M^{-1}cm^{-1}$

Therefore, the molar absorptivity coefficient is, $16.67 M^{-1}cm^{-1}$.