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Question 18N.3.hl.TZ0.b

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Date November 2018 Marks available [Maximum mark: 2] Reference code 18N.3.hl.TZ0.b
Level hl Paper 3 Time zone TZ0
Command term Outline Question number b Adapted from N/A
b.
[Maximum mark: 2]
18N.3.hl.TZ0.b

Scientists have developed various analytical techniques.

Ethanol in breath can be detected by a redox reaction. Outline this method of detection. An equation is not required.

[2]

Markscheme

ALTERNATIVE 1:

Any two of:

«blow through tube of» acidified «orange» potassium dichromate(VI)/K2Cr2O7/dichromate/Cr2O72– ✔

Cr(VI)/Cr6+/Cr2O72– reduced to Cr(III)/Cr3+✔

 

colour changes «from orange» to green

OR

colour change is monitored ✔

 

ALTERNATIVE 2:

oxygen reduced to water

OR

ethanol oxidized to ethanoic/acetic acid ✔

 

current measured ✔

 

Accept “ethanol oxidized to ethanal/acetaldehyde”.

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