DP Chemistry (last assessment 2024)

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Question 19N.2.hl.TZ0.f

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

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

Ozone depletion is catalysed by nitrogen monoxide, NO, which is produced in aircraft and motor vehicle engines, and has the following Lewis structure.

Show how nitrogen monoxide catalyses the decomposition of ozone, including equations in your answer.

[2]

Markscheme

•NO + O3 → •NO2 + O2 ✔

•NO2 + O3 → •NO + 2O2 ✔

NOTE: Accept •NO2 → •NO + •O AND •O + O3 → 2O2 for M2.

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