Chapter 17

Question 1

Explain how a mass spectrometer works

Answer 1

1. Sample is vaporised and then isonised to form positive ions
2. Ions are accelerated to the same kinetic energy KE = 1/2mv2
3. Ions are separated according to their mass. Heavier ions move slower than the lighter ions and take longer to reach the detector

Question 2

What is the highest mass peak called? (the one with the highest m/z ratio)

Answer 2

Molecular ion peak

Question 3

Why does the m+1 peak exist

Answer 3

1.1% of carbon is the carbon 13 isotope, making 1.1% of the molecules 1 heavier

Question 4

Which molecules will be recognised and which wont?

Answer 4

positive ions will be recognised. Uncharged radicals won’t

Question 5

What is mass spectroscopy used for?

Answer 5

Used in sport to test urine samples for banned substances

Question 6

describe how infrared spectroscopy works

Answer 6

-Covalent bonds have a specific frequency they vibrate at.
- They absorb infrared radiation at that frequency
-Infrared spectrocoper fires a range of wavelengths at it, and measures the absorption of the molecule

Question 7

What gasses absorb the earths reemitted IR radiation

Answer 7

Water vapour, carbon dioxide and Methane

Question 8

What is infrared spectroscopy used for?

Answer 8

breathalysers (measures C-H peak instead of O-H)