Question

(b) Data has been collected to show that at a given wavelength in a 1 cm pathlength cell, Beer's Law for the absorbance of Co2+ is linear. If a 0.135 M solution of Co2+ has an absorbance of 0.350, what is the concentration of a solution with an absorbance of 0.460?

Answer 1

Answer : The concentration of a solution with an absorbance of 0.460 is, 0.177 M

Explanation :

Using Beer-Lambert's law :

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

where,

A = absorbance of solution

C = concentration of solution

l = path length

$\epsilon$ = molar absorptivity coefficient

From this we conclude that absorbance of solution is directly proportional to the concentration of solution at constant path length.

Thus, the relation between absorbance and concentration of solution will be:

$\frac{A_1}{A_2}=\frac{C_1}{C_2}$

Given:

$A_1$ = 0.350

$A_2$ = 0.460

$C_1$ = 0.135 M

$C_2$ = ?

Now put all the given values in the above formula, we get:

$\frac{0.350}{0.460}=\frac{0.135}{C_2}$

$C_1=0.177M$

Therefore, the concentration of a solution with an absorbance of 0.460 is, 0.177 M