AS: Mass Spec

Question 1

How is the current generated in a Mass Spec?

Answer 1

• Electrons TRANSFERRED from the plate/detector

* to the + ion

Question 2

Isotope with the LOWEST ___ or _______ is deflected…

Answer 2

• m/z value
• mass

MORE in the MAGNETIC FIELD

Question 3

State 2 measurements recorded for each isotope:

Answer 3

• m/z value

* relative abundance

Question 4

What are the 5 stages of Mass Spec?

Answer 4

Vaporisation
Ionisation
Acceleration
Deflection
Detection

Question 5

Describe “Vaporisation”

Answer 5

Using heat to vaporise the sample

Question 6

Describe “Ionisation”

Answer 6

sample is BOMBARDED with electrons at HIGH SPEED using an ELECTRON GUN which KNOCKS OUT an ELECTRON and forms + ion

Question 7

Describe “Acceleration”

Answer 7

positive ions accelerate using ELECTRIC FIELD

Question 8

Describe “Deflection”

Answer 8

+ ions’ path altered by MAGNETIC FIELD

• Lighter ions - less momentum - deflected MORE
• ONLY ions with a m/z ratio make it to the detector

Question 9

Describe “Detection”

Answer 9

Magnetic Field strength SLOWLY ⬆️. Different ions reach detector. MASS SPECTRUM is produced.

Question 10

Write out the equation for the First Ionisation Energy of Carbon

Answer 10

C (g) ➡️ C+ (g) + e-

Question 11

In a Mass Spectrometer, what is the relative abundance of each isotope proportional to?

Answer 11

The CURRENT generated by that ISOTOPE at the detector

Question 12

If the sample is an ELEMENT, what do each of the lines represent?

Answer 12

ISOTOPES of that element

Question 13

Why must the sample be IONISED?

Answer 13

• to ACCELERATE it

* to DEFLECT it