DP Chemistry (last assessment 2024)
Question 22M.2.sl.TZ1.f(iii)
| Date | May 2022 | Marks available | [Maximum mark: 1] | Reference code | 22M.2.sl.TZ1.f(iii) |
| Level | sl | Paper | 2 | Time zone | TZ1 |
| Command term | Justify, Outline | Question number | f(iii) | Adapted from | N/A |
f(iii).
[Maximum mark: 1]
22M.2.sl.TZ1.f(iii)
Magnesium is a reactive metal often found in alloys.
Iodomethane is used to prepare CH3Mg. It can also be converted into methanol:
CH3 + HO– → CH3OH + –
The polarity of the carbon–halogen bond, C–X, facilitates attack by HO–.
Outline, giving a reason, how the bond polarity changes going down group 17.
[1]
Markscheme
decreases/less polar AND electronegativity «of the halogen» decreases ✔
Accept “decreases” AND a correct comparison of the electronegativity of two halogens.
Accept “decreases” AND “attraction for valence electrons decreases”.
Examiners report
Another question that was not well answered with probably only a quarter of candidates stating that the polarity would decrease because of decreasing electronegativity down the group.
