CL 17- spectroscopy

Question 1

explain what happens to a covalent bond when IR is passed through the sample

Answer 1

IR makes bonds vibrate more strongly

Question 2

what are the most abundant greenhouse gases in the atmosphere and how do these contribute to global warming?

Answer 2

CO₂, water and methane
* they absorb IR, which makes the bonds vibrate
* they can then re-emit this energy as radiation which increases the earth’s temperature

Question 3

explain how infrared spectroscopy can be used to monitor gases causing air pollution (e.g. CO and NO from car emissions)

Answer 3

CO + NO from car emissions can be identified using remote sensors that analyse the IR of a gas sample, use their sprectral fingerprints

Question 4

explain how infrared radiation can be used in modern breathalysers to measure ethanol in the breath

Answer 4

• a sample of breath has the IR spectrum taken
• the strength of the absorption of IR due to bonds in the ethanol is measured

Question 5

explain which peak in a mass spectrum of an organic compound is the molecular ion peak

Answer 5

• the molecular ion peak is the peak with the highest m/z value
• it is produced by the whole molecule losing one electron
• it gives you the mr of the whole molecule