| Date | November 2009 | Marks available | 1 | Reference code | 09N.3.hl.TZ0.A1 |
| Level | HL | Paper | 3 | Time zone | TZ0 |
| Command term | Identify | Question number | A1 | Adapted from | N/A |
Question
\(^{\text{1}}{\text{H}}\,{\text{NMR}}\) and IR spectroscopy both involve the absorption of electromagnetic radiation.
Explain why tetramethylsilane (TMS) is used as a reference standard in \(^{\text{1}}{\text{H}}\,{\text{NMR}}\) spectroscopy.
Markscheme
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
Most G2 comments on Section A were about this question. Many commented that titration is not part of the SL syllabus; however it is the expectation that students would cover this and other basic chemical techniques as part of their practical programme. Question 1 in all papers is meant to be data response and students will be expected to be familiar with experimental techniques. Also, there was some confusion caused because there was one sample and three titres. However this unfortunate cause of confusion did not seem to impact on candidate performance as poor performance was found throughout the question even with some very routine questions. Generally this question was poorly answered. In a) not many candidates managed to write the correct balanced equation, however many gave the correct species that were missing, H+ and H2O. Most candidates were able to identify the reducing agent although a few candidates just mentioned ‘iron’ or Fe, but metallic iron was not in the equation.
