4.2.4 analytical techniques

Question 1

what is infrared spectroscopy and how is it used

Answer 1

• measures certain bonds in a molecule absorbing infrared radiation at characteristic frequencies that cause covalent bonds to vibrate
• a computer then compares IR spectra to a database to identify the compound

Question 2

what is the greenhouse effect

Answer 2

• CO2, methane and water vapour are greenhouse gases and they trap the Earth’s radiated IR energy in the atmosphere
• the IR radiation is absorbed by C=O, O-H and C-H bonds which then contribute to global warming

Question 3

what contribution does CO2 have to global warming

Answer 3

• concentrations of CO2 in the atmosphere have risen significantly due to increased burning of fossil fuels
• the greenhouse effect id dependent on the amount of CO2 in the atmosphere, its ability to absorb IR and how long it stays in the atmosphere

Question 4

how can infrared spectroscopy be used practically

Answer 4

• to monitor gases causing air pollution

- modern breathalysers to measure levels of ethanol in the breath

Question 5

what is the process of mass spectrometry

Answer 5

• when a molecule is put through a mass spectrometer it will break up to give a series of peaks caused by fragments
• the peak with the largest m/z is equal to the Mr and is called the molecular ion peak

Question 6

what is fragmentation

Answer 6

• the molecular ion fragments due to covalent bonds breaking

- more stables ions like carbocations will cause a greater peak intensity