One type of ‘breathalyser’ instrument used by police for the measurement of the concentration of alcohol in a driver’s breath is a fuel cell. An acidic electrolyte is used. Ethanol is oxidised to ethanoic acid at one electrode and oxygen from the air is converted to water at the other.
The overall equation for this reaction is
C₂H₅OH(aq) + O₂(g) → CH₃COOH(aq) + H₂O(l)

Write the equation for the half reaction at the anode.
Solution
A motorist who has consumed alcohol blows into the fuel cell. If the breath entering the cell provides alcohol at the rate of 3.0 × 10–^-5 g per second, calculate the maximum current, in amps, that the cell would produce.
Solution

The nature of the electrodes in the cell is essential to the effective operation of the breathalyser. State two important functions that the electrodes must perform.
Function 1
Function 2
Solution