| Date | May 2012 | Marks available | 2 | Reference code | 12M.3.hl.TZ1.A1 |
| Level | HL | Paper | 3 | Time zone | TZ1 |
| Command term | Identify and State | Question number | A1 | Adapted from | N/A |
Question
Analytical techniques are very useful in determining molecular structures. A compound, X, has the empirical formula \({{\text{C}}_{\text{2}}}{{\text{H}}_{\text{4}}}{\text{O}}\).
Peaks in a \(^{\text{1}}{\text{H}}\,{\text{NMR}}\) spectrum are measured relative to a reference standard. State the name of a substance used and identify one property that makes it particularly suitable for this application.
Markscheme
tetramethylsilane/TMS;
Any of these for second mark:
strong single peak (as there are 12 protons in identical chemical environment);
absorbs upfield/away from most other protons/H’s;
low boiling point/bp / volatile (so easily removed from sample);
not toxic / unreactive / does not interfere with sample;
Examiners report
The reference standard for NMR and the reasons for its choice were well known.
