Brainscape's Knowledge GenomeTM

Browse over 1 million classes created by top students, professors, publishers, and experts.


See full index

atomic structure 3.1.1 > mass spectrometry > Flashcards

mass spectrometry Flashcards

1
Q

what is mass spectrometry?

A

a powerful instrumental method of analysis

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
2
Q

what can mass spectrometry be used for?

2 things

A
  1. to find the abundance and mass of each isotope in an element therefore allowing us to determine its relative atomic mass (Ar)
  2. find the relative molecular mass of substances made of molecules
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
3
Q

What happens in time of flight mass spectrometry?

A

Particles of the substance are ionised to form 1 + which are accelerated towards a negatively charged plate. then the time taken to travel a fixed distance is used to find the mass of each ion in the sample

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
4
Q

Why are the particles ionised?

A

so that each particle will have the same kinetic energy

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
5
Q

How is the time taken to travel a fixed distance used to find the mass of an ion?

A

As all ions have the same kinetic energy and the distance is fixed, bigger items will arrive at the plates slower and lighter atoms will arrive at the plate faster

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
6
Q

What are the four stages of mass spectrometry?

A
  1. ionisation
  2. acceleration
  3. flight tube
  4. detection
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
7
Q

What are the two techniques of ionisation?

A

Electron impact or electrospray ionisation

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
8
Q

What is the method for an electron impact?

4 things

A
  1. the sample being analysed is vaporised
  2. Then, high energy electrons are fired at it using an electron gun
  3. These high energy electrons knock of one electron from each particle performing a 1+ ion
  4. These particles are then attracted towards and negatively charged plate at which they are accelerated at
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
9
Q

How are electrons fired at a sample in electron impact?

A

Using an electron gun

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
10
Q

What is an electron gun?

A

A hot wire filament with a current running through it

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
11
Q

What is the electron impact equation?

2 ways

A

X(g) + e- –> X+(g) + 2e-
or
X(g) –> X+(g) +e-

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
12
Q

what type of substances is electron impact used on?

A
  1. elements

2. substances with low formula masses (Mr)

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
13
Q

What are the downsides of using an electron impact?

A

It can cause molecule fragmentation because of the spectrometer is very destructive and high energy

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
14
Q

What is the method for electrospray ionisation?

5 things

A
  1. the sample is dissolved in a volatile solvent
  2. It is then injected through a hypodermic needle to get a fine mist or aerosol
  3. The tip of the needle is then attached to a positive terminal of high-voltage power supply
  4. the particles gain a proton from the solvent as they leave the needle forming 1+ ions
  5. The particles are then attracted towards a negative plate which they are accelerating towards
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
15
Q

How would you determine the MR of the sample ionised by electrospray ionisation on a mass spectrum?

A

by taking 1 off the highest peak on the mass spectrum as the substance has gained a proton

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
16
Q

What is the equation for electrospray ionisation?

A

X(g) + H+ –> XH+ (g)

17
Q

What type of substance is electrospray ionisation used on?

A

Substances with a high molecular mass

18
Q

Why is electro spray ionisation known as soft ionisation?

A

Because fragmentation rarely occurs

19
Q

In the kinetic energy equation what units is kinetic energy measured in?

A

joules

20
Q

in the kinetic energy equation what is mass measured in?

A

Kilograms

21
Q

In the kinetic energy equation what is velocity measured in?

A

Metres per second -1

22
Q

What happens in stage three, the flight tube?

ion drift

A

The positive ions travel through a hole in the negatively charged plate into a tube.

23
Q

In the time of flight equation what is time measured in?

A

Seconds

24
Q

In the time of flight equation what is distance measured in?

A

Metres

25
Q

What happens in stage four, detection?

A

The positive ions hit a negatively charged electric plate. When they hit the detector plate, the positive ions are discharged by gaining electrons from the plate which turns them back into atoms. This generates a movement of electrons and hence an electric current is measured. The size of the current gives a measure of the number of ions hitting the plate

26
Q

What is the mass spectrum?

A

A computer produced a set of data

27
Q

What does the mass spectrum show?

A

The mass to charge ratio and the abundance of each ion that reaches the detector

28
Q

What are the lines called on the mass spectrum graph?

A

Peaks

29
Q

On which axis is the mass to charge ratio on?

A

X axis

30
Q

On which axis is the relative abundance on?

A

Y axis

31
Q

what is an isotope?

A

atoms of the same element with the same number of protons but different numbers of neutrons

atomic structure 3.1.1 (5 decks)

Brainscape helps you reach your goals faster, through stronger study habits.
© 2024 Bold Learning Solutions. Terms and Conditions