C17- Spectroscopy

Question 1

What increases the amount of vibration in a covalent bond

Answer 1

Temperature

Question 2

Two types of bond vibration

Answer 2

Bend

Stretch

Question 3

What does the amount that a bond bends/stretches depend on

Answer 3

The mass of the atoms in a bond- heavier atoms vibrate slower

Strength of the bond- Stronger bonds vibrate faster

Question 4

What frequency of IR does a chemical bond absorb

Answer 4

a bond will only absorb the same frequency of IR as the natural frequency of the bond

Question 5

Greenhouse gases in the atmosphere and IR radiation

Answer 5

Some of the suns radiation is reemitted from earth’s surface in longer wavelnegth IR

Greenhouse gases absorb this longer wavelength IR

Vibrating bonds then re emit the IR as temperature

Question 6

Applications of IR

Identify and measure pollutants

Answer 6

Remote sensors identify vehicle emissions

monitors localised pollutions

Question 7

Applications of IR

Breathalysers

Answer 7

Measure compounds inbreath such as ethanol

Can measure strength, as more IR absorbed means higher the reading and strength

Question 8

Elemental analysis

Answer 8

Using percentage composition data to determine empirical formula

Question 9

Mass spectroscopy

Answer 9

Use of molecular ion peak from a mass spectrum to determine molecular mass

Question 10

IR spectroscopy

Answer 10

Use of absorption peaks from IR spectrum to identify bond and functional groups

Question 11

What does a mass spectrometer detect

Answer 11

The mass to charge ratio of the molecular ion

This gives the molecular mass of the compound

Does not detect radicals

Question 12

How to find the M+ peak on a mass spectrum

Answer 12

Clear peak at the highest m/z value

Question 13

Why is there a M+1 peak on a mass spectrum

Answer 13

1.1% of carbon atoms are the carbon 13 isotope

This increases molecular mass by 1

Question 14

What is fragmentation in a mass spectrum

Answer 14

Molecular ions break down into smaller pieces

Question 15

What does fragmentation break a molecule into

Answer 15

A positively charged fragment ion

and a radical

Question 16

Values of a CH2+ and C2H5+ fragment

Answer 16

15

29

Question 17

Values of a CH2OH+ and a CH3CHOH+ fragment

Answer 17

31

45

Answer 18

The sun porduces mainly UV vsible and IR radiation which is partially refglected bvack to space when it reaches earth

Sme is absorbed by earth surface, heating it up

The earth emits this energy back out as IR

The IR radiation emitted by the earth can be absorbed by gases in the troposphere and become trappped

IR radiation is then re emitted in all directions some back towards earth, causing a heating effect