Infrared Spectroscopy: Effect on Molecules

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What types of vibrations occur in molecules when irradiated with IR radiation?

Rotational and translational vibrations

Stretching and bending vibrations (correct)

Symmetric and asymmetric vibrations

Vibrations in the UV region

In which region of the spectrum does ultraviolet radiation lie?

High energy side of the visible spectrum (correct)

Low energy side of the visible spectrum

Far IR region

Between visible and infrared spectrum

What type of energy is largely associated with infrared radiation?

Mechanical energy

Electromagnetic energy

Chemical energy

Thermal energy (correct)

What property of molecules can be determined using IR spectroscopy?

Functional groups Signup and view all the answers

What law can be used to predict the oscillation frequency in molecules?

Hooke's Law Signup and view all the answers

How are IR spectra usually recorded?

Transmittance vs wave number (cm-1) Signup and view all the answers

Which factor affects the vibrational frequency of a molecule according to Hook's Law?

Force constant Signup and view all the answers

What happens to the vibrational frequency when the bond strength of a molecule increases?

Vibrational frequency increases Signup and view all the answers

Which type of molecules have changing or fluctuating dipole moments during vibration and are considered IR active?

Molecules with heteronuclear bonds Signup and view all the answers

What is the formula to calculate the total degree of freedom for a linear molecule?

3N - 5 Signup and view all the answers

Which type of molecules are considered IR inactive due to having no dipole moment?

Homonuclear molecules Signup and view all the answers

What is the essential condition for a molecule to be IR active according to the provided text?

Changing or fluctuating dipole moment during vibration Signup and view all the answers

Why do IR spectra appear upside down and right to left?

Because of the nature of IR radiation absorption Signup and view all the answers

What is the essential condition for a molecule to be IR-active?

Possessing a fluctuating dipole moment during vibration Signup and view all the answers

How many total degrees of freedom does a molecule with N atoms have?

$3N$ Signup and view all the answers

Why are homonuclear diatomic molecules not IR-active?

They do not have a fluctuating dipole moment Signup and view all the answers

What kind of vibrations give rise to absorption in the IR region?

Vibrations that cause a fluctuating dipole moment Signup and view all the answers

Why do fewer bands appear in the IR spectra than theoretically possible?

Because certain vibrations are not observed Signup and view all the answers