List two benefits of linolenic acid to humans.

Calculate the iodine number for linolenic acid, C₁₇H₂₉COOH \(({M_{\text{r}}} = 278.48)\).

The condensed structural formula of linolenic acid is given in table 22 of the data booklet.

assists brain function;

enables normal growth/development;

involved in synthesis of prostaglandins;

reduces (risk of) heart disease/blockage of arteries;

lowers blood pressure;

reduces LDL cholesterol;

increases HDL cholesterol;

Do not accept bad/good instead of LDL/HDL.

\({{\text{n}}_{{\text{iodine}}}} = {\text{3}}{{\text{n}}_{{\text{linolenic acid}}}}\);

\({\text{iodine number}}\left( {\frac{{3 \times 100 \times 253.8}}{{278.48}}} \right) = 273{\text{ (g)}}\);

Award [2] for final correct answer.

If an alternative definition, in terms of moles/C=C bonds is given, award [1 max] for iodine number = 3.

The benefits of linolenic acid were reasonably well known especially its effect on lowering LDL cholesterol and many candidates scored full marks for this part of the question although in some cases, one of the marks was not achieved due to LDL not being specified. The definition of iodine number sometimes proved challenging with some confusion of mass and moles of iodine. The expected definition of the iodine number is the mass in grams of iodine reacting with 100g of oil. Overall, students did find the calculation of the iodine number challenging.

The benefits of linolenic acid were reasonably well known especially its effect on lowering LDL cholesterol and many candidates scored full marks for this part of the question although in some cases, one of the marks was not achieved due to LDL not being specified. The definition of iodine number sometimes proved challenging with some confusion of mass and moles of iodine. The expected definition of the iodine number is the mass in grams of iodine reacting with 100g of oil. Overall, students did find the calculation of the iodine number challenging.