| Date | May 2011 | Marks available | 2 | Reference code | 11M.3.sl.TZ1.F1 |
| Level | SL | Paper | 3 | Time zone | TZ1 |
| Command term | Deduce | Question number | F1 | Adapted from | N/A |
Question
Fats and vegetable oils are triesters of glycerol with fatty acids. Many of these acids contain 18 carbon atoms. The table shows the relative percentages of various \({{\text{C}}_{{\text{18}}}}\) fatty acid chains in four common fats and oils.
Deduce which fat or oil from the table could best be described as:
saturated
mono-unsaturated
poly-unsaturated.
Hydrogenation can result in the formation of trans fatty acids. Outline the meaning of the term trans fatty acids and explain why their formation is undesirable.
Markscheme
saturated: Tallow;
mono-unsaturated: Olive oil;
poly-unsaturated: Linseed oil;
3 correct award [2], 2 correct award [1], no marks for just one correct.
fats with trans configuration across the double bond;
not easily digested / accumulate in body tissue / increase LDL cholesterol levels;
Do not accept “bad cholesterol”.
Examiners report
Quite a few candidates could correctly identify the relative degree of saturation of the oils, though some thought they had to include all four in their answer. The meaning of shelf life was quite well known, in addition many realised that increasing unsaturation decreased shelf life and could suggest ways of increasing it. The conditions requiredcfor hydrogenation were not well appreciated, especially the need for a catalyst, and few could write any specific details regarding trans-fats apart from the fact there were health concerns regarding these.
Quite a few candidates could correctly identify the relative degree of saturation of the oils, though some thought they had to include all four in their answer. The meaning of shelf life was quite well known, in addition many realised that increasing unsaturation decreased shelf life and could suggest ways of increasing it. The conditions requiredcfor hydrogenation were not well appreciated, especially the need for a catalyst, and few could write any specific details regarding trans-fats apart from the fact there were health concerns regarding these.
