DP Chemistry (last assessment 2024)

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Question 18M.3.sl.TZ2.14

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Date May 2018 Marks available [Maximum mark: 2] Reference code 18M.3.sl.TZ2.14
Level sl Paper 3 Time zone TZ2
Command term Deduce, Outline Question number 14 Adapted from N/A
14.
[Maximum mark: 2]
18M.3.sl.TZ2.14

One method of producing biodiesel is by a transesterification process.

(a)

Deduce the equation for the transesterification reaction of pentyl octanoate, C7H15COOC5H11, with methanol.

[1]

Markscheme

C7H15COOC5H11(l) + CH3OH(l) → C7H15COOCH3(l) + C5H11OH(l)

OR

C13H26O2(l) + CH4O(l) → C9H18O2(l) + C5H12O(l)

OR

M18/4/CHEMI/SP3/ENG/TZ2/14.a/M

 

Accept correct equation in any format eg, skeletal, condensed structural formula, etc.

Accept equations with equilibrium arrow.

[1 mark]

 

(b)

Outline why the ester product of this reaction is a better diesel fuel than pentyl octanoate.

[1]

Markscheme

less viscous «and so does not need to be heated to flow»

OR

less likely to undergo incomplete combustion

OR

fewer intermolecular/London/dispersion forces

OR

vaporizes easier

 

Ignore equation and products in 14a.

Accept “van der Waals’/vdW” for “London”.

[1 mark]

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