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.

Explanation:

A = Absorbance of solution

E = Molar absorptivity

l = Length of cuvette = 1 cm

c = Concentration of solution

Beer's law is given by

The equation of a straight line is given by

Comparing the above equations we get

Value on axis = A = Absorbance of solution = 0.23

= Slope of line = El = Molar absorptivity multiplied with length =

= Value of x axis = c = Concentration of solution

So we get

The molar concentration of the sample is

i'm pretty sure its b i might be wrong though!

your answer is a. the enthalpy of formation for a pure element in its standard state is always positive.