IR Spectroscopy

Question 1

What type of interaction ( response ) do photons have when they interact with the IR section of the EM spec?

Answer 1

Vibrations

Question 2

what is the IR region of the EM spectrum?

Answer 2

700nm - 1mm

Question 3

what do the peaks correspond to on the spectrum?

Answer 3

vibrations of different bonds

Question 4

what happens when a sample is exposed to IR radiation?

Answer 4

The bonds within the molecule will absorb photons

Question 5

describe the different 3 different forms of vibrations demonstrated by molecules that absorb IR radiation ?

Answer 5

symmetric stretching
asymmetric stretching
symmetric bend

Question 6

What does the force constant represent ?

Answer 6

the stiffness of a bond and the bond strength

Question 7

How many different vibrations are there for non-linear molecules ( lie in 3 different axis )

Answer 7

3N-6

Question 8

How many different vibrations are there for linear molecules ( lie in only 2 different axis )

Answer 8

3N-5

Question 9

what are stretching modes

Answer 9

vibrations due to changes in bond lengths

Question 10

what are bending modes

Answer 10

vibrations that occur due to changes in the bond angles

Question 11

what are inferred active modes and what does it require?

Answer 11

they are the only modes that can be detected by IR activity - the must cause a change in the electronic movement of the molecule