DP Chemistry (last assessment 2024)
Question 18M.3.sl.TZ2.a
| Date | May 2018 | Marks available | [Maximum mark: 3] | Reference code | 18M.3.sl.TZ2.a |
| Level | sl | Paper | 3 | Time zone | TZ2 |
| Command term | Explain | Question number | a | Adapted from | N/A |
a.
[Maximum mark: 3]
18M.3.sl.TZ2.a
Carbon dioxide is a product of the combustion of petrol.
Explain the molecular mechanism by which carbon dioxide acts as a greenhouse gas.
[3]
Markscheme
Any three of:
IR/long wavelength/low frequency radiation radiated/emitted by the Earth’s «surface absorbed in the bonds»
bond length/C=O changes
OR
«asymmetric» stretching of bonds
OR
bond angle/OCO changes
polarity/dipole «moment» changes
OR
dipole «moment» created «when molecule absorbs IR»
«some of» energy is then re-radiated towards «the surface of the» Earth
Do not accept terms such as “reflect” OR “bounced” OR “trapped”.
[3 marks]
