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2.4Inorganic Chemistry

Reactivity Series — Edexcel Linear - OL (Chemistry) Revision Notes & Topical Questions

10 min read 14 parts Lesson 11 of 23 Unit quiz

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Lesson summary

The Reactivity Series: Reactions of Metals — EDEXCEL LINEAR – OL (CHEMISTRY) notes: Use observations of metal reactions with water, steam, acids and salt solutions to build and apply the reactivity series.The reactivity series lists metals from most to least reactive: potassium, …

  • Worked example 1
  • Worked example 2
  • Worked example 3
  • Worked example 4
  • Displacement
  • Thermite reaction

Part 1 of 6Ordering metals by reactivity

The reactivity series lists metals from most to least reactive: potassium, sodium, lithium, calcium, magnesium, aluminium, (carbon), zinc, iron, (hydrogen), copper, silver, gold. Reactivity is the tendency of a metal to lose electrons and form positive ions. Position is judged by how vigorously a metal reacts with oxygen, water, acids and by displacement.

Part 2 of 6Reactions with oxygen, water and dilute acid

MetalWith cold waterWith steamWith dilute acid
Potassium, sodium, lithiumVery vigorous, hydroxide + H2—Explosive
CalciumSteady fizzing, calcium hydroxide (milky)—Vigorous
MagnesiumVery slowBurns brightly, oxide + H2Fast fizzing
ZincNoneReacts, oxide + H2Steady bubbles
IronNone (rusts slowly)Reacts slowly (reversible with H2)Slow bubbles
Copper, silver, goldNoneNoneNone

Equations

  • Ca + 2H2O → Ca(OH)2 + H2;
    • Mg + H2O(g) → MgO + H2;
    • Zn + 2HCl → ZnCl2 + H2.

Reactions with oxygen, water and dilute acid
A metal gives hydrogen with acid only if it is above hydrogen in the series.
Reactions with oxygen form metal oxides: 2Mg + O2 → 2MgO (white ash, bright white flame), while copper forms black CuO only on strong heating.

Collecting hydrogen

  • test with a lit splint, which gives a squeaky pop.
  • Rate of bubbling or temperature rise provides a way to rank metals when the acid and its concentration are kept the same.

Part 3 of 6Displacement reactions

A more reactive metal displaces a less reactive metal from solutions of its salts, and from its oxide on heating.

Displacement reactions
Example: magnesium added to copper(II) sulfate gives a colourless solution and a brown/pink deposit: Mg + CuSO4 → MgSO4 + Cu.
Iron nails in copper sulfate are coated in copper and the blue colour fades to pale green as iron(II) sulfate forms.

Results can be arranged in a grid.

Displacement reactions
For metals A, B, C and D, count how many other metals each displaces: the metal displacing most is highest.
In the thermite reaction aluminium displaces iron from iron(III) oxide (2Al + Fe2O3 → Al2O3 + 2Fe) releasing enough heat to melt the iron, used to weld rails.

Part 4 of 6Reactivity and metal compounds

The more reactive the metal, the more stable its compounds. Carbonates and hydroxides of reactive metals (sodium, potassium) resist heating; those of less reactive metals (copper carbonate → copper oxide + carbon dioxide) decompose readily. Metal nitrates decompose similarly, with copper nitrate giving brown nitrogen dioxide. This ties reactivity to extraction method in the later lesson.

Part 5 of 6Practical investigation: ranking metals fairly

To rank metals by their reaction with acid, use equal-sized pieces (or equal masses) of each metal, the same volume and concentration of dilute hydrochloric acid at the same starting temperature, and measure either the time taken to produce a fixed volume of hydrogen or the temperature rise.

Practical investigation: ranking metals fairly
Metals are placed in order from the fastest to the slowest.
Repeat the measurements and calculate means, and use a gas syringe or an upturned measuring cylinder over water to collect the gas.

Safetywear eye protection, use small quantities of the very reactive metals, never put potassium or sodium into acid, and keep flames away from hydrogen.

Practical investigation: ranking metals fairly
A variable such as the surface area (powder versus ribbon) must be controlled because a larger surface area increases rate without changing a metal’s position in the series.
Results with reactive metals are best described as a trend rather than an exact number,
  • since exothermic reactions heat the acid and speed the reaction further.

Part 6 of 6Worked examples

  1. Describe and explain what happens when a piece of zinc is placed in iron(II) sulfate solution. [3]3 marks

  2. Place the metals in order of reactivity: X reacts with cold water, Y reacts only with steam, Z does not react with steam or acid. [2]2 marks

  3. Write the equation for the reaction of magnesium with dilute hydrochloric acid and give the test for the gas. [3]3 marks

  4. Why does copper not react with dilute sulfuric acid? [1]1 mark

Key terms

TermMeaning
Reactivity seriesRanking of metals by their reactivity
DisplacementA more reactive element pushing out a less reactive one
Thermite reactionAluminium reducing iron(III) oxide to give molten iron
Squeaky popTest for hydrogen with a lit splint
OxideCompound of an element with oxygen
VigorousFast reaction with rapid bubbling or heating

Avoid these mistakes

1
Saying all metals react with dilute acid — copper, silver and gold do not.
2
Mixing up the reaction of magnesium with cold water and steam.
3
Forgetting to state which metal is displaced in displacement reactions.
4
Putting carbon or hydrogen in the order as metals but forgetting they are only reference points.

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