DP Chemistry (first assessment 2025)
Question 19M.2.HL.TZ2.a
| Date | May 2019 | Marks available | [Maximum mark: 2] | Reference code | 19M.2.HL.TZ2.a |
| Level | HL | Paper | 2 | Time zone | TZ2 |
| Command term | Describe | Question number | a | Adapted from | N/A |
a.
[Maximum mark: 2]
19M.2.HL.TZ2.a
Describe the effect of infrared (IR) radiation on carbon dioxide molecules.
[2]
Markscheme
bond length/C=O distance changes
OR
«asymmetric» stretching «of bonds»
OR
bond angle/OCO changes [✔]
polarity/dipole «moment» changes
OR
dipole «moment» created «when molecule absorbs IR» [✔]
Note: Accept appropriate diagrams.
Examiners report
This part was fairly well answered with most candidates receiving one of the two marks. There were many candidates who stated asymmetric stretching and bonds vibrate but missed writing polarity and dipole changes, which deprived them of the second mark.
Syllabus sections
Reactivity 3. What are the mechanisms of chemical change? » Reactivity 3.2—Electron transfer reactions » Reactivity 3.2.9—Functional groups in organic compounds may undergo oxidation. Deduce equations to show changes in the functional groups during oxidation of primary and secondary alcohols, including the two-step reaction in the oxidation of primary alcohols.