(U2) Infrared Spectroscopy

Question 1

What is ground state?

Answer 1

A molecular vibration which is in the lowest possible energy state

Question 2

What is wavenumber?

What is it measured in?

Answer 2

The reciprocal of wavelength and it is measured in cm^-1

Question 3

What is the affect of heating up bonds?

Answer 3

They vibrate:

• bond stretching and
• bond bending

Thus absorbing infrared radiation

Question 4

Why are the absorptions of bonds different?

i.e. what does it depend on?

Answer 4

• different bonds vibrate in a different way, involving different amounts of energy
• stretching and bending depends on bond length (e.g. C=C is shorter than C-C) and mass of atoms at either end

Question 5

What is the cause of the fingerprint region?

What can it be used to find?

Answer 5

• The manner of bending vibrations within a molecule
• used to identify identical molecules