Reactivity series

O Level / IGCSE Chemistry · Metals. A short explanation of the idea, the rules to remember, the mistake to avoid, a worked example and practice questions with answers.

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The idea

The reactivity series lists metals in order of how readily they react. The more reactive a metal is, the more easily its atoms lose electrons to form positive ions. Carbon and hydrogen are included as reference points, although they are non-metals.

The position of a metal tells you what it does. Metals near the top react with cold water; those above hydrogen react with dilute acids; those below hydrogen do not. A more reactive metal will displace a less reactive metal from a solution of its salt, because the more reactive metal forms ions more readily.

Aluminium seems unreactive because a thin, tough layer of aluminium oxide sticks to its surface and keeps water and acids away from the metal.

Rules to remember

Common mistake

Expecting a reaction when the metal added is less reactive than the metal in the solution: copper does not react with zinc sulfate solution. Compare the two positions in the series before you decide.

Worked example

1.3 g of zinc powder is added to excess aqueous copper(II) sulfate. What mass of copper is formed? (Cu 64, Zn 65)

  1. Zinc is above copper in the series, so it displaces copper: Zn + CuSO4 → ZnSO4 + Cu (1 mol of Zn gives 1 mol of Cu).
  2. Moles of Zn = 1.3 ÷ 65 = 0.020 mol, so moles of Cu = 0.020 mol.
  3. Mass of Cu = 0.020 × 64 = 1.28 g.

Answer: 1.28 g of copper.

Practice questions

Try each one, then open the answer.

1. Magnesium is more reactive than copper. What does this mean in terms of ions?

  1. A
    magnesium atoms have more protons than copper atoms
  2. B
    magnesium atoms gain electrons more readily than copper atoms
  3. C
    magnesium atoms lose electrons more readily than copper atoms do
  4. D
    copper atoms form positive ions more readily than magnesium atoms
Show answer

Answer: C. Reactivity of metals is their tendency to form positive ions. That is why magnesium displaces Cu2+: Mg + Cu2+ → Mg2+ + Cu.

2. Metal X displaces metal Y from an aqueous solution of Y sulfate. Metal Z displaces metal X from an aqueous solution of X sulfate. What is the order of reactivity, most reactive first?

  1. A
    Y, X, Z
  2. B
    X, Z, Y
  3. C
    Y, Z, X
  4. D
    Z, X, Y
Show answer

Answer: D. A more reactive metal displaces a less reactive one from solution. Z displaces X, so Z is more reactive than X; X displaces Y, so X is more reactive than Y. The order is Z, X, Y.

3. Which metal reacts with cold water to give hydrogen and a hydroxide?

  1. A
    calcium
  2. B
    aluminium
  3. C
    zinc
  4. D
    copper
Show answer

Answer: A. Calcium (Group II) reacts with cold water: Ca + 2H2O → Ca(OH)2 + H2. Zinc reacts only with steam, copper does not react, and aluminium is protected by its oxide layer.

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