User interface language: English | Español

Date May 2017 Marks available 2 Reference code 17M.3.sl.TZ2.8
Level SL Paper 3 Time zone TZ2
Command term Explain Question number 8 Adapted from N/A

Question

Sunflower oil contains stearic, oleic and linoleic fatty acids. The structural formulas of these acids are given in section 34 of the data booklet.

Explain which one of these fatty acids has the highest boiling point.

[2]
a.

10.0 g of sunflower oil reacts completely with 123 cm3 of 0.500 mol dm–3 iodine solution. Calculate the iodine number of sunflower oil to the nearest whole number.

[3]
b.

Markscheme

stearic acid AND chain has no kinks/more regular structure
OR
stearic acid AND it has straight chain
OR
stearic acid AND no C=C/carbon to carbon double bonds
OR
stearic acid AND saturated
OR
stearic acid AND chains pack more closely together

stronger London/dispersion/instantaneous induced dipole-induced dipole forces «between molecules»

 

Accept “stearic acid AND greater surface area/electron density”.

M2 can only be scored if stearic acid is correctly identified.

Accept “stronger intermolecular/van der Waals’/vdW forces”.

[2 marks]

a.

«n(I2) = 0.123 dm3 x 0.500 mol dm–3 =» 0.0615 «mol»

«m(I2) = 0.0615 mol x 253.8 g mol–1 =» 15.6 «g»

«iodine number = 15.6  g × 100 10.0  g » = 156

 

Award [3] for correct final answer.

Iodine number must be a whole number.

Award [2 max] for 78.

[3 marks]

b.

Examiners report

[N/A]
a.
[N/A]
b.

Syllabus sections

Options » B: Biochemistry » B.3 Lipids
Show 52 related questions
Core » Topic 4: Chemical bonding and structure » 4.4 Intermolecular forces
Options » B: Biochemistry
Core » Topic 4: Chemical bonding and structure
Core
Options

View options