Displacement reactions involving metal oxides
3 marks · NormalIron(III) oxide reacts with aluminium powder in a competition (thermite) reaction. Aluminium is above iron in the reactivity series.
Explain, in terms of reactivity, why aluminium can remove oxygen from iron(III) oxide but iron cannot remove oxygen from aluminium oxide.
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Aluminium is more reactive than iron, so it displaces iron from iron(III) oxide. Iron is less reactive than aluminium, so it cannot displace aluminium from aluminium oxide.
Also accept: Aluminium is above iron in the reactivity series and can reduce iron(III) oxide; iron is below aluminium and cannot reduce aluminium oxide.
Common mistakes: Saying only that 'aluminium is more reactive' without comparing with iron
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Marking points
M1 · 1 mark · States or implies comparison using reactivity series (aluminium more reactive than iron).
A1 · 1 mark · Correctly explains that aluminium can remove oxygen from iron(III) oxide because it is more reactive.
A2 · 1 mark · States or explains that iron cannot remove oxygen from aluminium oxide because iron is less reactive than aluminium.
Worked solution
Aluminium is more reactive than iron, so it can reduce iron(III) oxide to iron by removing its oxygen. Iron is less reactive than aluminium, so it cannot reduce aluminium oxide. Only a more reactive metal can displace a less reactive metal from its oxide.