Question

A Beer's Law Plot of sample A gives a slope equal to 1.2 M-1cm-1. Calculate molar concentration of this sample at a wavelength of 420 nm and an absorbance reading of 0.23 in a 1 cm cuvette.

Answer 1

Answer:

$0.192\ \text{M}$

Explanation:

A = Absorbance of solution

E = Molar absorptivity

l = Length of cuvette = 1 cm

c = Concentration of solution

Beer's law is given by

$A=Elc$

The equation of a straight line is given by

$y=mx+c$

Comparing the above equations we get

Value on $y$ axis = A = Absorbance of solution = 0.23

$m$ = Slope of line = El = Molar absorptivity multiplied with length = $1.2\times 1\ \text{M}^{-1}$

$x$ = Value of x axis = c = Concentration of solution

So we get

$c=\dfrac{A}{El}\\\Rightarrow c=\dfrac{0.23}{1.2\times 1}\\\Rightarrow c=0.192\ \text{M}$

The molar concentration of the sample is $0.192\ \text{M}$