The molar absorptivity for aqueous solutions of phenol at 211 nm is 6.17x103l/mol/cm. calculate the linear range of phenol concentrations if the transmittance is to be less than 85% and greater than 7% when the measurements are made in 1cm cell.

Explanation:

The given data is as follows.

          = 211 nm,          

           l = 1 cm,             7% < Transmittance < 85%

Suppose the aqueous solution follows Lambert-Beer's law. Therefore,

                   Absorbance =

Hence, for 7% transmittance the value of absorbance will be as follows.

                  Absorbance =

                            = 1.155

For 85% transmittance the value of absorbance will be as follows.

                 Absorbance =

                            = 0.07058

According to Lambert-Beer's law.

                  A =

where,       A = absorbance

                  = molar extinction coefficient

                 C = concentration

Therefore, concentration for 7% absorbance is as follows.

                  =

                                  =

                                  = 0.187 mmol/L

Concentration for 85% absorbance is as follows.

                  =

                                  =

                                  = 0.01144 mmol/L

Thus, we can conclude that linear range of phenol concentration is 0.01144 mmol/L to 0.187 mmol/L.

the answer is 75.0%.