The presence of alcohol in the breath can be detected using a breathalyzer.

Any three of:
ethanol «in breath» is oxidized «to ethanoic acid» $✔$
electrons pass through external circuit/meter**$✔$**
«to cathode where» O2 is reduced**$✔$**
current is proportional to alcohol concentration**$✔$**

**Note:**Accept equations for oxidation of ethanol or reduction of oxygen.

Bond:
C–O
OR
C–H $✔$

Reason:
cannot use O–H bonds as in water «found in breath»$✔$

Note:Accept “C–O/C–H «bonds in molecules in breath» most likely to be in ethanol”.

Do not apply ECF here.