Question

The number of vibrational mode(s) of a carbon dioxide molecule that can be detected using infrared spectroscopy is

• A. 1
• B. 2
• C. 3
• D. 4

Hint:

In infrared spectroscopy, only vibrational modes that cause a change in dipole moment are IR-active. CO$_2$ has three such modes.

Answer 1

The Correct Option is C

Step 1: Understanding molecular vibrational modes.
For a molecule like CO$_2$, it has several vibrational modes, including stretching and bending vibrations.
Step 2: Analyzing CO$_2$ molecule.
A CO$_2$ molecule has three vibrational modes that are IR-active: two asymmetric stretching modes and one bending mode.
Step 3: Conclusion.
Thus, the correct number of vibrational modes detectable in IR spectroscopy for CO$_2$ is 3. The correct answer is (C) 3.