Question 19M.3.hl.TZ1.b(ii)
| Date | May 2019 | Marks available | [Maximum mark: 1] | Reference code | 19M.3.hl.TZ1.b(ii) |
| Level | hl | Paper | 3 | Time zone | TZ1 |
| Command term | Suggest | Question number | b(ii) | Adapted from | N/A |
Lithium has many uses.
The emission spectra obtained by ICP-OES for a mixture containing the isotope 6Li (Li-6) and naturally occurring lithium (Li (N)) is shown.
Suggest why ICP-OES does not give good quantitative results for distinguishing 6Li from naturally occurring lithium.
[1]
emission spectra of both «6Li and natural Li» give same colour/produce same «range of» wavelengths
OR
they have same electron transitions/same nuclear charge [✔]
Note: Accept “the spectra are almost identical”.
Most candidates correctly identified the type of bonding and the colour of the emission spectrum of lithium, but frequently referred to the ICP-OES spectra of 6Li and naturally occurring lithium as being the same, rather than similar and thus failed to score the mark in (b)(ii).
