# 2: Ultraviolet/Visible Absorption Spectroscopy

Learning Objectives

After completing this unit the student will be able to:

• Compare and contrast atomic and molecular spectra.
• Explain why atomic spectra consist of lines whereas molecular spectra at room temperature are broad and continuous.
• Justify the difference in molecular spectra at room temperature and 10 K.
• Describe the cause of Doppler broadening.
• Determine the effect of conjugation on a UV/Vis absorption spectrum.
• Determine the effect of non-bonding electrons on a UV/Vis absorption spectrum.
• Determine the effect of solvent on the energy of $$n-pi^*$$ and $$\pi-\pi^*$$ transitions.
• Evaluate the utility of UV/Vis spectroscopy as a qualitative and quantitative method.
• Describe a procedure by which UV/Vis spectroscopy can be used to determine the pKa of a weak acid.