A simplified absorption spectrum for an unknown diatomic gas is verbally described as…
CHEMISTRY · Multi-part · A Level · Chemistry · Organic analysis and spectroscopy · Organic analysis and spectroscopy
Problem
A simplified absorption spectrum for an unknown diatomic gas is verbally described as follows.
• The horizontal axis is wavelength, extending logarithmically from 0.1 µm up to 3 cm.
• The vertical axis is unitless absorbance.
• Three dominant peaks are labelled:
– Peak A at 1.2 cm
– Peak B at 3.0 µm
– Peak C at 450 nm
• No other significant features are observed.
Answer the following questions about this spectrum.
(a) For each labelled peak, identify the type of molecular energy transition (rotational, vibrational, or electronic) that most likely produced the absorption. Clearly explain the reasoning behind each identification, citing relevant relationships between wavelength and transition energy.
(b) Rank Peaks A, B, and C in order of increasing photon energy absorbed. Justify your ranking qualitatively without performing numerical calculations.
(c) Describe one experimental parameter that could be adjusted to resolve additional fine structure within Peak A and explain why this adjustment would be effective.