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Question 18N.3.sl.TZ0.7b.i

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Date November 2018 Marks available [Maximum mark: 3] Reference code 18N.3.sl.TZ0.7b.i
Level sl Paper 3 Time zone TZ0
Command term Determine Question number b.i Adapted from N/A
b.i.
[Maximum mark: 3]
18N.3.sl.TZ0.7b.i

Lipids play several roles in our bodies.

(b.i)

The iodine number is the maximum mass of iodine that reacts with 100 g of an unsaturated compound.

Determine the iodine number of stearidonic acid, C17H27COOH.

[3]

Markscheme

ALTERNATIVE 1:

4 C=C bonds/4 carbon to carbon double bonds ✔

mass of iodine per mole of acid = «4 × 253.80 g mol–1 =» 1015.2 «g mol–1» ✔

iodine number «= 1015.2 g mo l − 1 276.46 g mo l − 1 × 100 » = 367 ✔

 

ALTERNATIVE 2:

4 C=C bonds/4 carbon to carbon double bonds ✔

« 100 g 276.46 g mo l − 1 × 4 =» 1.447 mol of I2 «reacts with 100 g» ✔

iodine number «= 1.447 mol × 253.80 g mol–1» = 367 ✔

Award [3] for correct final answer.

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