Question 22M.2.hl.TZ2.c
| Date | May 2022 | Marks available | [Maximum mark: 2] | Reference code | 22M.2.hl.TZ2.c |
| Level | hl | Paper | 2 | Time zone | TZ2 |
| Command term | Describe | Question number | c | Adapted from | N/A |
Carbon forms many compounds.
Describe a test and the expected result to indicate the presence of carbon–carbon double bonds.
[2]
ALTERNATIVE 1:
Test:
add bromine «water»/Br2 (aq) ✔
Result:
«orange/brown/yellow» to colourless/decolourised ✔
Do not accept “clear” for M2.
ALTERNATIVE 2:
Test:
add «acidified» KMnO4 ✔
Result:
«purple» to colourless/decolourised/brown ✔
Accept “colour change” for M2.
ALTERNATIVE 3:
Test:
add iodine / ✔
Result:
«brown» to colourless/decolourised ✔
Well answered by most, but some basic chemistry was missing when reporting results, perhaps as a result of little practical work due to COVID. A significant number suggested IR spectrometry, very likely because the question followed one on H NMR spectroscopy, thus revealing a failure to read the question properly (which asks for a test). Some teachers felt that adding "chemical" would have avoided some confusion.