In the extraction of lead, lead(II) oxide is reduced by reaction with carbon monoxide gas: PbO + CO → Pb + CO2 Which substance is oxidised in this reaction?

Answer: B. Step 1: Recall the oxygen-based definitions At Core level: - Oxidation = gain of oxygen - Reduction = loss of oxygen Step 2: Track the oxygen in the equation PbO + CO → Pb + CO2 - Lead(II) oxide, PbO, starts with one oxygen atom and ends u…

Redox Reactions: Question 6

Syllabus 6.4

Multiple choice Core 1 mark

In the extraction of lead, lead(II) oxide is reduced by reaction with carbon monoxide gas:

$\text{PbO} + \text{CO} \rightarrow \text{Pb} + \text{CO}_2$

Which substance is oxidised in this reaction?

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Step 1: Recall the oxygen-based definitions

At Core level:

Oxidation = gain of oxygen
Reduction = loss of oxygen

Step 2: Track the oxygen in the equation

$\text{PbO} + \text{CO} \rightarrow \text{Pb} + \text{CO}_2$

Lead(II) oxide, $\text{PbO}$ , starts with one oxygen atom and ends up as lead metal, $\text{Pb}$ , with none. It has lost oxygen.
Carbon monoxide, $\text{CO}$ , starts with one oxygen atom and ends up as carbon dioxide, $\text{CO}_2$ , with two. It has gained oxygen.

Step 3: Apply the definitions

Gaining oxygen is oxidation, so carbon monoxide is the substance that is oxidised. Lead(II) oxide, which loses oxygen, is reduced. Carbon monoxide is acting as the reducing agent in this reaction (the reducing agent is always the substance that is itself oxidised).

Final answer

Carbon monoxide, $\text{CO}$ , is oxidised, option B.