Pre-Assignments

1. Under which conditions does the Beer-Lambert law become additive?
2. If absorbance of two components is 0.80 at an isosbestic point wavelength, what is the ratio of individual component’s absorbance values at that wavelength?
3. What will happen to the absorbance if two components having equimolar composition have the same molar absorptivity at a particular wavelength?
4. Write down the necessary absorbance equations for a three-component solution.
5. Is this multicomponent sample analysis principle applicable to any pair of light absorbing samples?

Post-Assignments

1. Determine two isosbestic points for coumarin 343 and coumarin 6.
2. Why was it necessary to determine the molar absorptivities of a substance at two different wavelengths?
3. Could your selection of two different wavelengths, λ ₁ and λ ₂ , for your calculation of unknown concentrations be completely random? Why?
4. How will you prepare a solution containing 1:1 (v/v) mixture of 2.5×10 ^-5 M coumarin 343 and 2.0×10 ^-5 M coumarin 6?
5. Suppose 2 mL of a component is mixed with equal volume of another component. The first component has absorbance A ₁ and the second component has absorbance A ₂ at a particular wavelength. What will be the absorbance of the binary mixture at that particular wavelength?