Spectra of gaseous chlorine monoxide (ClO) were obtained in three separate…
CHEMISTRY · Multi-part · A Level · Chemistry · Organic analysis and spectroscopy · Organic analysis and spectroscopy
Problem
Spectra of gaseous chlorine monoxide (ClO) were obtained in three separate experiments under identical temperature and pressure conditions. The reported absorption maxima are:
• Microwave region: 2.20 cm (Peak M)
• Infrared region: 2.87 µm (Peak V)
• Ultraviolet–visible region: 395 nm (Peak E)
Assume that each peak reflects the lowest-energy transition available within its respective region.
(a) Calculate the photon energy associated with each peak in J photon−1, using three significant figures.
(b) Determine the ratio EV/EM and the ratio EE/EV. Comment on what each ratio reveals about the relative spacing of rotational, vibrational, and electronic energy levels.
(c) Using your results, explain why microwave spectra often display many closely spaced lines while UV–visible spectra for the same molecule typically exhibit broad, featureless bands.
(d) Suppose the sample temperature were decreased substantially while all other conditions remained constant. Predict qualitatively how the appearance of Peak M would change and defend your prediction with reference to molecular energy level populations.