How do you determine molar absorptivity of cobalt nitrate?

Answer 1

Utilizing the Beer-Lamber Law you have A=abc

here A= is the absorbance at a set wavelength

a= the molar absorbtivity

b= the path length

c= concentration in molar

The best way to determine a is to make solutions of known concentrations of cobalt nitrate (3-5 would be best) and determine the absorbance of each solution.

Next plot the Abs vs concentration of each solution using something like excel or R. Determine the line of best fit ( it's important to force fit this line through 0) the R-sqr value should be no less than .95

Since the equation of a line is : y=mx +b, this is equivalent to A=abc noting that b is assumed to be 1cm we habe A=ac, where m=a and x=c

In short the slope of the line of best fit in the molar absorbtivity

Answer 2

Molar absorptivity is determined by measuring the absorbance of a known concentration of cobalt nitrate solution at a specific wavelength using a spectrophotometer. The molar absorptivity (ε) is calculated using Beer-Lambert's Law, A = εlc, where A is the absorbance, ε is the molar absorptivity, l is the path length of the sample, and c is the concentration of the solution.