Chapter 7 - Modern analytical techniques (L)

Question 1

What is the molecular ion peak?

Answer 1

The peak furthest to the right (the one with the highest m/z)

Question 2

What causes the molecular ion peak?

Answer 2

When an organic molecule loses an electron in the mass spectrometer- this can occur when an electron collides with the molecule, knocking out an electron so forming a positive ion

Question 3

What does the m/z value of the molecular ion peak indicate?

Answer 3

The relative molecular mass of the molecule (as it has just lost an electron)

Question 4

What causes the M+1 peak?

Answer 4

The naturally occurring isotope of carbon (carbon-13).

Question 5

What is the M+1 peak?

Answer 5

A very small peak just to the right of the molecular ion peak

Question 6

What is fragmentation?

Answer 6

Where the molecular ion breaks into smaller pieces

Question 7

What is the base peak?

Answer 7

The peak with the greatest abundance (the tallest peak)

Question 8

What are the two possible effects of infrared radiation on bonds?

Answer 8

Stretching and bending

Question 9

What is stretching?

Answer 9

Where the bond length increases and decreases

Question 10

What is bending?

Answer 10

Where the bond angle increases and decreases

Question 11

What type of molecules do not absorb infrared radiation?

Answer 11

Non-polar molecules such as H2 and Cl2

Question 12

What is infrared radiation?

Answer 12

Part of the electromagnetic spectrum with frequencies below that of red light

Question 13

What is the transmittance value?

Answer 13

The value in an infrared spectrum that represents the amount of infrared radiation not absorbed (transmitted) at a particular wave number. Often done as a 0-100 percentage

Question 14

What is the wave number?

Answer 14

The wave number represents the frequency of the infrared radiation that was absorbed by a particular bond in a molecule

Question 15

What is the intensity of an infrared absorption refer to?

Answer 15

The actual amount of infrared radiation absorbed. A high intensity refers to a low transmittance value and a low intensity refers to a high transmittance value

Question 16

What are the 4 stages of mass spectrometry?

Answer 16

Ionisation
Acceleration
Deflection
Detection

Question 17

What happens in the ionisation stage of mass spectrometry?

Answer 17

The atom or molecule is ionised by knocking one or more electrons off to form a positive ion

Question 18

What happens in the acceleration stage of mass spectrometry?

Answer 18

The ions are accelerated so that they all have the same kinetic energy

Question 19

What happens in the deflection stage of mass spectrometry?

Answer 19

The ions are then deflected by a magnetic field according to their masses and amount of positive charge.

Question 20

What happens in the detection stage of mass spectrometry?

Answer 20

The beam of ions passing through the machine is detected electrically.

Question 21

How does the amount of positive charge on the atom/molecule affect of deflection?

Answer 21

The more the ion is positively charged, the more it gets deflected.