Assume the molar absorptivity (ε) for CoCl42- at 700 nm is 446.9 M-1 cm-1. If d, the cell path length, is equal to 0.71 cm for the cuvettes being used, and if the measured absorbance (A) at 700 nm is 0.935, what is [CoCl42-]?

Answer : The concentration of [CoCl₄]²⁻ is,

Explanation :

Using Beer-Lambert's law :

where,

A = absorbance of solution  = 0.935

C = concentration of solution = ?

l = path length = 0.71 cm

= molar absorptivity coefficient =

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

Therefore, the concentration of [CoCl₄]²⁻ is,