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

`0.192\ \text{M}`

Step-by-step 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* 1\ \text{M}^(-1)`

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

So we get

`c=(A)/(El)\\\Rightarrow c=(0.23)/(1.2* 1)\\\Rightarrow c=0.192\ \text{M}`

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