Question

Use the absorbance value for the unknown FD&C Blue $1$ stock solution to determine the concentration of the solution.

Answer 1

A stock solution is prepared from which four solutions of known concentration will be made. The absorbance of each will be measured. When a graph of absorbance vs concentration is plotted for the known solutions, as shown above. This is called a calibration plot since all concentrations are known. The linearity of this plot arises from the Bee-Lambert.

Law: $A=ElC$

$E$= molar absorptivity coefficient of $FD$ & $C$ Blue $1$ at $630$ nm

By locating the absorbance of the unknown solution on the verical axis of the graph, the corresponding concentration can be found on the horizontal axis.