Question

Student measured the absorbance of the substance X depending on its concentration in solution. She used 0.2 cm cuvette. Her calibration curve is a straight line with the slope 2.3·103 M-1. The extinction coefficient of substance X in this solution is:

Answer 1

The extinction coefficient is 1.15 x 10⁴ M⁻¹.cm⁻¹ (value is not rounded off)

Step-by-step explanation:

According to Lambert-Beer law

`A = ε.b.C`

Here, A is absorbance, ε is extinction coefficient, b is the length of the cuvette and C is the molar concentration of substance X.

This equation is used for the relation between concentration and absorbance of electromagnetic radiation absorbing species. It is a linear equation and can be used for making a calibration curve, which is used for the analysis of an unknown concentration solution. The slope of this curve according to the equation is the product of extinction coefficient (M⁻¹.cm⁻¹) and the length of the cuvette in cm.

In this problem, the slope is provided, which can be mathematically represented as:

`slope =  ε.b`

`2.3 X 10^(3)M^(-1) = ε.(0.2 cm)`

`ε = 1.15 X 10^(4) M^(-1).cm^(-1)` (not rounded off)

`ε = 1 X 10^(4) M^(-1).cm^(-1)` (rounded off)