DP Chemistry (last assessment 2024)

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Question 19N.3.hl.TZ0.16

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Date November 2019 Marks available [Maximum mark: 4] Reference code 19N.3.hl.TZ0.16
Level hl Paper 3 Time zone TZ0
Command term Discuss, Outline Question number 16 Adapted from N/A
16.
[Maximum mark: 4]
19N.3.hl.TZ0.16

Consider the following data for butane and pentane at STP.

(a)

Discuss the data.

[3]

Markscheme

«similar specific energy and» pentane has «much» larger energy density ✔

Any two for [2 max]:
similar number of bonds/«C and H» atoms in 1 kg «leading to similar specific energy» 
OR
 only one carbon difference in structure «leading to similar specific energy» ✔
NOTE: Accept “both are alkanes” for M2.

pentane is a liquid AND butane is a gas «at STP» ✔
NOTE: Accept “pentane would be easier to transport”.

1 m3 of pentane contains greater amount/mass than 1 m3 of butane ✔
NOTE: Accept “same volume” for “1 m3” and “more moles” for “greater amount” for M4.

(b)

Outline what is meant by the degradation of energy.

[1]

Markscheme

energy converted to heat
OR
energy converted to less useful/dispersed forms
OR
energy converted to forms that have lower potential to do work
OR
heat transferred to the surroundings ✔

NOTE: Reference to energy conversion/transfer required. Do not accept reference to loss of energy.

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