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Date May 2019 Marks available 2 Reference code 19M.3.hl.TZ2.18
Level HL Paper 3 Time zone TZ2
Command term Describe Question number 18 Adapted from N/A

Question

This question is about global warming.

Describe the effect of infrared (IR) radiation on carbon dioxide molecules.

[2]
a.

Outline one approach to controlling industrial emissions of carbon dioxide.

[1]
b.

Markscheme

bond length/C=O distance changes
OR
«asymmetric» stretching «of bonds»
OR
bond angle/OCO changes [✔]

polarity/dipole «moment» changes
OR
dipole «moment» created «when molecule absorbs IR» [✔]

 

Note: Accept appropriate diagrams.

a.

Any one of:
capture where produced «and store» [✔]

use scrubbers to remove [✔]

use as feedstock for synthesising other chemicals [✔]

carbon credit/tax/economic incentive/fines/country specific action [✔]

use alternative energy
OR
stop/reduce use of fossil fuels for producing energy [✔]

use carbon reduced fuels «such as methane» [✔]

increase efficiency and reduce energy use [✔]

 

Note: Do not accept “planting more trees”.

Accept specific correct examples.

b.

Examiners report

This part was fairly well answered with most candidates receiving one of the two marks. There were many candidates who stated asymmetric stretching and bonds vibrate but missed writing polarity and dipole changes, which deprived them of the second mark.

a.

This part was reasonably answered although there were many candidates who gave vague answers that did not receive marks.

b.

Syllabus sections

Options » C: Energy » C.5 Environmental impact—global warming
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Options » C: Energy
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