Chemistry lab

Question

The molar extinction coefficient of a complex of iron is 12,000 L mol-1 cm-1 with minimum detectable absorbance 0.01. What is the minimum concentration needed for minimum detection in a cell of path length 1.00 cm?

Answer 1

Nelson, I think you use Beer's Law: Here is an example of directly using the Beer's Law Equation (Absorbance = e L c) when you were given the molar absorptivity constant (or molar extinction coefficient). In this equation, e is the molar extinction coefficient. L is the path length of the cell holder. c is the concentration of the solution.

 

.01 = (12,000 L mol^-1 cm^-1)(1.00 cm)(c)

 

c = .01/(12000 x 1.00)    =  .01/12000 = 8.33 x 10^-7 moles/liter