DP Chemistry (last assessment 2024)

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Question 19N.2.hl.TZ0.1d

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Date November 2019 Marks available [Maximum mark: 2] Reference code 19N.2.hl.TZ0.1d
Level hl Paper 2 Time zone TZ0
Command term Discuss Question number d Adapted from N/A
d.
[Maximum mark: 2]
19N.2.hl.TZ0.1d

The equations show steps in the formation and decomposition of ozone in the stratosphere, some of which absorb ultraviolet light.


Step 1    O2 → 2O•

Step 2    O• + O2 → O3

Step 3    O3 → O• + O2

Step 4    O• + O3 → 2O2

(d)

Discuss how the different bond strengths between the oxygen atoms in O2 and O3 in the ozone layer affect radiation reaching the Earth’s surface.

[2]

Markscheme

«bond» in O2 stronger than in O3 ✔


ozone absorbs lower frequency/energy «radiation than oxygen»
OR
ozone absorbs longer wavelength «radiation than oxygen» ✔

 

NOTE: Accept ozone «layer» absorbs a range of frequencies.

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