Oxidation and reduction
2 marks · EasyA student heats 5.0 g of lead in a stream of oxygen and forms 5.4 g of lead(II) oxide, according to the equation:
Calculate the mass of oxygen that has combined with the lead. State, in terms of oxygen transfer, what has happened to the lead.
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(a) 0.4 g of oxygen has combined with the lead. g
(b) The lead is oxidised (it has gained oxygen). · must show Reference to gain of oxygen OR to oxidation
Common mistakes: Subtracting the wrong way round for mass of oxygen; Saying reduced instead of oxidised
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Marking points
A1 · 1 mark · Correct subtraction: 5.4 - 5.0 = 0.4 (g oxygen)
B1 · 1 mark · Lead is oxidised (because it has gained oxygen, or oxidation is gain of oxygen).
Worked solution
Mass of oxygen combined = mass of lead(II) oxide formed - mass of lead used = 5.4 g - 5.0 g = 0.4 g
The lead gains oxygen during this reaction, so it is oxidised.