Question

a) The use of spectrophotometry to scan a solution that contains an organic dye will show which wavelengths in the visible spectrum that organic dye most strongly absorbs. Then, using the relationship between energy and wavelength that you learned in Chapter 6,

E = hc/λ

you could convert each wavelength to its corresponding energy. If you found that an organic dye compound strongly absorbs at 566 nm , what is the energy that corresponds to the excitation of an electron from the HOMO to the LUMO in that compound?

Express the energy in joules to three significant figures.

b)

After determining the energies involved in the transition between the HOMO and the LUMO for each compound, you will need to test whether there is a correlation between the length of the π system and the excitation energy. Indicate how you might graph your data to determine whether this relationship exists.

Spell out the full name of the variable needed to complete the graph.

It would be possible to test the existence of a relationship by plotting the excitation energy vs. number of __________ (fill in blank) in the π system.