4.2.4 Analytical Techniques

Question 1

How does IR radiation affect covalent bonds?

Answer 1

Bonds can absorb IR radiation which makes them bend or stretch more.

Question 2

How do greenhouse gases increase the temperature of the atmosphere?

Answer 2

Some radiation is re-emitted from the Earth’s surface as longer-wavelength IR radiation.
Water vapour, CO2 and methane absorb this radiation as it has same frequency as their bonds.
Vibrating bonds in the molecules eventually emit this energy as radiation that heats the atmosphere.

Question 3

How can pollution be measured with IR spectra?

Answer 3

Remote sensors analyse IR spectra of vehicle emissions to detect and measure CO, CO2 and hydrocarbons in busy town centres/motorways.

Question 4

How can IR spectra be used in breathalysers?

Answer 4

Beam of IR radiation passed through breath and check IR absorbance of compounds in the breath.
Characteristic bonds present in ethanol detected, more absorbed = higher reading = more alcohol on breath.

Question 5

How to find molecular mass on mass spectra.

Answer 5

Find the molecular ion peak (highest m/Z value)