Reactivity Series & Corrosion Of Metals

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Notes

Reactivity Series

The **reactivity series** lists metals in order of their reactivity based on reactions with water and acids.
Non-metals **carbon** and **hydrogen** are included for extraction and displacement contexts.
Order (most to least reactive): **K, Na, Ca, Mg, Al, C, Zn, Fe, H, Cu, Ag, Au**.
Mnemonic: “Please send cats, monkeys and cute zebras into hot countries signed Gordon”.
Metals above hydrogen react with dilute HCl; those below do not.
More reactive metals react more vigorously with water and acids.

Reactions with Water and Steam

**K, Na, Ca** react with cold water: metal + water → metal hydroxide + hydrogen.
K reacts violently, Na quickly, Ca less strongly.
**Mg** reacts very slowly with cold water but vigorously with steam: Mg + H₂O → MgO + H₂.
Metals below Mg do not react with cold water or steam.

Reactions with Dilute Hydrochloric Acid

Metals above H in the series react: metal + 2HCl → metal chloride + H₂.
Mg, Zn, Fe react; Cu, Ag, Au do not.
Reaction vigour increases with reactivity: Mg > Zn > Fe.
K and Na react explosively with acids.

Displacement Reactions (Extended)

A more reactive metal **displaces** a less reactive metal from its salt solution.
More reactive metals lose electrons more easily (better reducing agents).
Example: Mg + CuSO₄ → MgSO₄ + Cu (blue solution fades, copper deposits).
No reaction occurs if the added metal is less reactive than the metal in the salt.
Displacement experiments can determine relative reactivity order.

Explaining Reactivity (Extended)

Reactivity depends on the **tendency to lose electrons** and form positive ions.
Metals high in the series lose electrons easily; low metals lose electrons with difficulty.
Aluminium appears less reactive due to a **protective oxide layer** (Al₂O₃).

Rusting of Iron

Rusting requires **iron, water, and oxygen**; product is **hydrated iron(III) oxide** (reddish-brown).
Word equation: iron + water + oxygen → hydrated iron(III) oxide.
Only iron or steel rusts; other metals **corrode** (not rust).
Investigating rusting: nail in air+water rusts; nail in boiled water+oil (no air) does not; nail with calcium chloride (no water) does not.

Rust Prevention: Barrier Methods

Barrier methods coat iron/steel to exclude water and oxygen.
Common barriers: **grease, oil, paint, plastic**.
If the coating is scratched, the iron is exposed and will rust.

Galvanising & Sacrificial Protection (Extended)

**Galvanising** coats iron with a layer of zinc (by electroplating or dipping in molten zinc).
Zinc forms ZnCO₃ barrier; if scratched, zinc provides **sacrificial protection**.
**Sacrificial protection** attaches a more reactive metal (e.g., zinc) to iron.
Zinc oxidises preferentially: Zn → Zn²⁺ + 2e⁻, protecting the iron.
Zinc blocks on ship hulls must be replaced periodically.

Particle arrangement in solids, liquids, and gases – relevant to understanding reactivity and corrosion conditions.

Practice questions

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1.Which word equation represents the rusting of iron?
Easy
- Airon + water + oxygen → hydrated iron(III) oxide
- Biron + water + hydrogen → hydrated iron(III) oxide
- Ciron + water + oxygen → hydrated iron(II) oxide
- Diron + water + hydrogen → hydrated iron(II) oxide
2.A student prepared four iron nails as explained below in an experiment to investigate rusting. She allowed the nails to rest in individual test tubes in a laboratory for one week. Which nail will show the greatest amount of rust?
Easy
- ADipped in water and allowed to dry.
- BDipped in paint and allowed to dry.
- CCoated in grease.
- DGalvanised with zinc.
3.Which of the following metals does NOT react with dilute hydrochloric acid?
Easy
- AMagnesium
- BZinc
- CCopper
- DIron
4.What is the chemical name for rust?
Easy
- AIron(II) oxide
- BIron(III) oxide
- CHydrated iron(III) oxide
- DHydrated iron(II) oxide
5.The diagram shows the experimental set-up a student used to investigate the composition of air. The student left the apparatus in the laboratory and observed that the water level had risen inside the test tube after one week. Which statement explains why the water level rose?
Medium
- ANitrogen monoxide was produced.
- BIron oxide was produced.
- CThe temperature of the water increased.
- DSulfur dioxide was produced.
6.A student investigates the reactivity of four different metals by adding a small piece of each metal to separate test-tubes containing aqueous iron(II) chloride. A tick (✓) indicates a reaction occurs. A cross (×) indicates no reaction occurs. Which row correctly predicts the results?
Medium
- Acopper: ×, magnesium: ✓, aluminium: ✓, zinc: ✓
- Bcopper: ✓, magnesium: ×, aluminium: ×, zinc: ×
- Ccopper: ×, magnesium: ✓, aluminium: ×, zinc: ✓
- Dcopper: ×, magnesium: ✓, aluminium: ✓, zinc: ×
7.Which of the following is a correct statement about the reactivity series?
Medium
- APotassium reacts more vigorously with cold water than calcium.
- BCopper reacts with steam to form copper oxide and hydrogen.
- CCarbon is more reactive than zinc.
- DGold reacts with dilute hydrochloric acid.
8.In the context of rust prevention, what is galvanising?
Medium
- ACoating iron with a layer of zinc.
- BAttaching a more reactive metal to iron.
- CPainting iron with oil.
- DPlating iron with copper.

More questions

9.Reactions of three metals and their oxides are shown in the table. metal reacts with cold water | metal oxide reacts with carbon P: no | no Q: no | yes R: yes | no What is the order of reactivity of the metals? (Least reactive → Most reactive)
Hard
- AP Q R
- BQ P R
- CQ R P
- DR P Q
10.Small blocks of zinc are attached to ship hulls made from steel to prevent rusting. Which statement explains this process?
Hard
- AZinc is higher up on the reactivity series than iron so has a higher tendency to become reduced.
- BZinc is lower down on the reactivity series than iron so has a higher tendency to become reduced.
- CZinc is higher up on the reactivity series than iron so has a higher tendency to become oxidised.
- DZinc is lower down on the reactivity series than iron so has a higher tendency to become oxidised.
11.The following section of the reactivity series shows a newly discovered element, Y. The only oxide of Y has the formula YO. Ca Mg Fe Y H Cu Which of the equations shows a reaction which would take place?
Hard
- A2Y(s) + Cu²⁺(aq) → 2Y⁺(aq) + Cu(s)
- BY(s) + Fe₂O₃(s) → 2Fe(s) + 3YO(s)
- CY(s) + 2HCl(aq) → YCl₂(aq) + H₂(g)
- DCu(s) + Y²⁺(aq) → Cu²⁺(aq) + Y(s)
12.Four different metals P, Q, R, and S were added to different aqueous solutions of their ions. The results are shown in the table (✓ = reaction, ✗ = no reaction). Metal | P²⁺ | Q²⁺ | R²⁺ | S²⁺ P | ✗ | ✗ | ✓ | ✓ Q | ✓ | ✗ | ✓ | ✓ R | ✗ | ✗ | ✗ | ✗ S | ✗ | ✗ | ✓ | ✗ What is the order of reactivity from most reactive to least reactive?
Hard
- AQ P S R
- BQ S P R
- CR P S Q
- DR S P Q
13.Four iron nails are placed in different conditions. Which nail will show the greatest amount of rust after one week?
Easy
- ADipped in water and allowed to dry.
- BDipped in paint and allowed to dry.
- CCoated in grease.
- DGalvanised with zinc.
14.In an experiment to investigate the composition of air, a student left iron nails in a test tube inverted over water. After one week, the water level inside the test tube rose. Which statement explains why the water level rose?
Easy
- ANitrogen monoxide was produced.
- BIron oxide was produced.
- CThe temperature of the water increased.
- DSulfur dioxide was produced.
15.A student adds zinc to copper(II) sulfate solution. Which observations are correct for this reaction?
Medium
- ASolution colour stays the same; pale grey crystals forming.
- BSolution turns darker blue; grey residue on the metal.
- CSolution turns orange/brown; blue crystals form on the metal.
- DSolution turns paler blue; orange/brown residue on the metal.
16.Four metals W, X, Y, Z are tested with dilute hydrochloric acid. Observations: W - slow reaction, X - violent reaction, Y - very slow reaction, Z - no reaction. Which row correctly identifies the metals?
Medium
- AW=iron, X=potassium, Y=silver, Z=aluminium
- BW=iron, X=potassium, Y=aluminium, Z=silver
- CW=aluminium, X=potassium, Y=iron, Z=silver
- DW=aluminium, X=potassium, Y=silver, Z=iron
17.Reactions of three metals and their oxides are shown in the table: metal reacts with cold water | metal oxide reacts with carbon P: no | no Q: no | yes R: yes | no What is the order of reactivity from least to most reactive?
Hard
- AP, Q, R
- BQ, P, R
- CQ, R, P
- DR, P, Q
18.Four metals P, Q, R, S are added to solutions of their ions. Results (✓ = reaction, ✗ = no reaction): Metal | P²⁺ | Q²⁺ | R²⁺ | S²⁺ P | ✗ | ✗ | ✓ | ✓ Q | ✓ | ✗ | ✓ | ✓ R | ✗ | ✗ | ✗ | ✗ S | ✗ | ✗ | ✓ | ✗ What is the order of reactivity from most to least reactive?
Hard
- AQ, P, S, R
- BQ, S, P, R
- CR, P, S, Q
- DR, S, P, Q
19.Small blocks of zinc are attached to steel ship hulls to prevent rusting. Which statement explains this process?
Hard
- AZinc is higher in the reactivity series than iron, so it has a higher tendency to become reduced.
- BZinc is lower in the reactivity series than iron, so it has a higher tendency to become reduced.
- CZinc is higher in the reactivity series than iron, so it has a higher tendency to become oxidised.
- DZinc is lower in the reactivity series than iron, so it has a higher tendency to become oxidised.
20.Which of the following metals reacts with cold water to form a metal hydroxide and hydrogen gas?
Easy
- AIron
- BZinc
- CCalcium
- DCopper
21.A student measures the temperature rise when 0.1 g of each metal is added to excess dilute hydrochloric acid. Results: Mg: +12°C, Zn: +6°C, Fe: +3°C, Cu: 0°C. Which metal is most reactive?
Medium
- AMg
- BZn
- CFe
- DCu
22.Which of the following displacement reactions will occur?
Medium
- ACopper + magnesium sulfate →
- BZinc + iron(II) chloride →
- CIron + zinc chloride →
- DSilver + copper(II) sulfate →
23.A bar chart shows the volume of hydrogen gas produced after one minute when five metals (P, Q, R, S, T) react with dilute hydrochloric acid. Volumes: P=15 cm³, Q=5 cm³, R=40 cm³, S=10 cm³, T=0 cm³. What is the order of reactivity from most to least reactive?
Hard
- AR, P, S, Q, T
- BP, R, S, Q, T
- CT, Q, S, P, R
- DT, S, Q, P, R
24.Which of the following is a correct method to prevent rusting by sacrificial protection?
Easy
- APainting the iron surface
- BCoating with oil
- CAttaching a block of magnesium to an iron pipe
- DPlating with tin
25.In an experiment to investigate rusting, four iron nails are placed in separate test tubes under different conditions. Which nail will rust the most after one week?
Medium
- AA nail dipped in water and then allowed to dry.
- BA nail dipped in paint and then allowed to dry.
- CA nail coated in grease.
- DA nail galvanised with zinc.
26.A student sets up an experiment with iron nails in a test tube inverted over water. After one week, the water level inside the test tube rises. What explains this rise?
Medium
- ANitrogen monoxide was produced.
- BIron oxide was produced.
- CThe temperature of the water increased.
- DSulfur dioxide was produced.
27.A student adds zinc to copper(II) sulfate solution. Which observations are correct?
Medium
- ASolution colour stays the same, pale grey crystals form.
- BSolution turns darker blue, grey residue on the metal.
- CSolution turns orange/brown, blue crystals form on the metal.
- DSolution turns paler blue, orange/brown residue on the metal.
28.Compound Y is heated with carbon in a test tube. A brown solid forms and limewater turns cloudy. What is compound Y?
Medium
- ACopper(II) oxide
- BCalcium oxide
- CMagnesium oxide
- DSodium oxide
29.Which row correctly shows how a metal reacts with dilute acid, cold water, and steam?
Hard
- ACopper: reacts with dilute acid ✓, reacts with cold water ×, reacts with steam ×
- BCalcium: reacts with dilute acid ×, reacts with cold water ✓, reacts with steam ✓
- CZinc: reacts with dilute acid ✓, reacts with cold water ×, reacts with steam ×
- DMagnesium: reacts with dilute acid ✓, reacts with cold water ×, reacts with steam ✓
30.Metals Q, R, S have these properties: Q reacts with cold water (yes), steam (yes), acid (violently); R reacts very slowly with cold water, slowly with steam, less strongly with acid; S reacts with none. What are Q, R, S?
Hard
- AQ: Potassium, R: Iron, S: Magnesium
- BQ: Sodium, R: Zinc, S: Copper
- CQ: Silver, R: Aluminium, S: Iron
- DQ: Calcium, R: Copper, S: Gold
31.A student adds four metals to separate samples of aqueous iron(II) chloride. Which row correctly predicts whether a reaction occurs? (✓ = reaction, × = no reaction)
Hard
- Acopper: ×, magnesium: ✓, aluminium: ✓, zinc: ✓
- Bcopper: ✓, magnesium: ×, aluminium: ×, zinc: ×
- Ccopper: ×, magnesium: ✓, aluminium: ×, zinc: ✓
- Dcopper: ×, magnesium: ✓, aluminium: ✓, zinc: ×
32.Reactions of three metals and their oxides are shown: P: metal + cold water (no), metal oxide + carbon (no); Q: metal + cold water (no), metal oxide + carbon (yes); R: metal + cold water (yes), metal oxide + carbon (no). What is the order of reactivity (least to most)?
Hard
- AP, Q, R
- BQ, P, R
- CQ, R, P
- DR, P, Q
33.The reactivity series shows a newly discovered element Y between Fe and H: Ca, Mg, Fe, Y, H, Cu. Which equation shows a reaction that will take place?
Hard
- A2Y(s) + Cu²⁺(aq) → 2Y⁺(aq) + Cu(s)
- BY(s) + Fe₂O₃(s) → 2Fe(s) + 3YO(s)
- CY(s) + 2HCl(aq) → YCl₂(aq) + H₂(g)
- DCu(s) + Y²⁺(aq) → Cu²⁺(aq) + Y(s)
34.Four metals P, Q, R, S are added to solutions of their ions. Results (✓ = reaction, ✗ = no reaction): P with P²⁺(✗), Q²⁺(✗), R²⁺(✓), S²⁺(✓); Q with P²⁺(✓), Q²⁺(✗), R²⁺(✓), S²⁺(✓); R with all ✗; S with P²⁺(✗), Q²⁺(✗), R²⁺(✓), S²⁺(✗). What is the order of reactivity (most to least)?
Hard
- AQ, P, S, R
- BQ, S, P, R
- CR, P, S, Q
- DR, S, P, Q
35.In the reactivity series, which non-metal is included to help extract metals from their oxides?
Medium
- Acarbon
- Bnitrogen
- Coxygen
- Dsulfur
36.During rusting, iron is oxidised. What does this mean?
Medium
- AIron loses electrons
- BIron gains electrons
- CIron gains oxygen
- DIron loses oxygen
37.Which statement about galvanising is correct?
Medium
- AIt coats iron with a layer of zinc
- BIt coats iron with a layer of tin
- CIt involves attaching a more reactive metal to iron
- DIt involves painting iron with oil
38.Which of the following is a correct barrier method to prevent rusting?
Medium
- Agrease
- Bgalvanising
- Csacrificial protection
- Delectroplating with zinc
39.Aluminium is high in the reactivity series but reacts slowly with dilute acids. Why?
Hard
- AIt has a protective layer of aluminium oxide
- BIt is less reactive than zinc
- CIt forms a protective layer of aluminium hydroxide
- DIt reacts with water instead
40.In a displacement reaction, zinc is added to copper(II) sulfate solution. What colour change is observed?
Hard
- AThe blue solution becomes colourless
- BThe colourless solution becomes blue
- CThe solution turns green
- DThe solution turns brown

Slides

Reactivity Series of Metals

Metals can be placed in order of reactivity based on their reactions with water and acids.
The reactivity series includes the non-metals carbon and hydrogen for extraction and acid reactions.
The order from most to least reactive is: K, Na, Ca, Mg, Al, C, Zn, Fe, H, Cu, Ag, Au.
A mnemonic: 'Please send cats, monkeys and cute zebras into hot countries signed Gordon'.

Which metal is the most reactive in the reactivity series?

Calcium
Potassium
Magnesium
Zinc

Reactions with Water and Steam

Potassium, sodium, and calcium react with cold water to produce metal hydroxide and hydrogen gas.
Potassium reacts violently, sodium quickly, and calcium less strongly.
Magnesium reacts very slowly with cold water but reacts with steam to form magnesium oxide and hydrogen.
Metals below magnesium do not react with water or steam.

Potassium reacts with cold water to form potassium ____ and hydrogen gas.

Reactions with Dilute Hydrochloric Acid

Metals above hydrogen in the reactivity series react with dilute HCl to form a salt and hydrogen gas.
The more reactive the metal, the more vigorous the reaction.
Metals below hydrogen (copper, silver, gold) do not react with dilute HCl.
Examples: Mg + 2HCl → MgCl2 + H2; Zn + 2HCl → ZnCl2 + H2; Fe + 2HCl → FeCl2 + H2.

Which metal does NOT react with dilute hydrochloric acid?

Magnesium
Zinc
Copper
Iron

Displacement Reactions

A more reactive metal can displace a less reactive metal from a solution of its salt.
The more reactive metal loses electrons more easily and acts as a reducing agent.
Example: Mg + CuSO4 → MgSO4 + Cu (blue solution fades, brown copper forms).
No reaction occurs if the added metal is less reactive than the metal in the salt.

What is observed when zinc is added to iron(II) chloride solution?

No reaction
A grey solid forms and solution becomes colourless
A brown solid forms and solution becomes green
Bubbles of gas

Rusting of Iron

Rusting is the reaction of iron with water and oxygen to form hydrated iron(III) oxide (rust).
Both water and oxygen must be present for rusting to occur.
Rusting is an oxidation reaction (iron loses electrons).
Only iron or steel can rust; other metals corrode.

Which conditions are necessary for rusting?

Water only
Oxygen only
Both water and oxygen
Carbon dioxide

Investigating Rusting

Three test tubes: nail in air and water (rusts), nail in boiled water with oil (no oxygen, no rust), nail with calcium chloride (no water, no rust).
Only the nail exposed to both air and water rusts.
Oil layer prevents air from entering; calcium chloride absorbs moisture.

In the rusting experiment, which nail rusts?

Nail in air and water
Nail in boiled water with oil
Nail with calcium chloride
None

Rust Prevention: Barrier Methods

Rust can be prevented by coating iron with barriers that stop water and oxygen reaching the metal.
Common barriers: grease, oil, paint, plastic.
If the coating is scratched, the iron underneath is exposed and will rust.

Coating iron with ____ prevents rust by keeping out water and oxygen.

Sacrificial Protection

A more reactive metal attached to iron will corrode first, protecting the iron.
Zinc is used on steel ships: zinc oxidises instead of iron.
Zinc loses electrons: Zn → Zn²⁺ + 2e⁻; iron is not oxidised.
Zinc blocks need replacement when corroded.

Why does zinc protect iron from rusting?

Zinc is less reactive than iron
Zinc is more reactive than iron and oxidises instead
Zinc forms a barrier
Zinc reacts with water

Galvanising

Galvanising is coating iron with a layer of zinc (by electroplating or dipping in molten zinc).
Zinc reacts with oxygen and CO₂ to form ZnCO₃, which acts as a barrier.
If the coating is scratched, the zinc still protects the iron by sacrificial protection.

Which statements about galvanising are true?

It coats iron with zinc.
It only works if the coating is undamaged.
Zinc carbonate acts as a barrier.
Scratched coating still protects iron.

Which metal would be suitable for sacrificial protection of iron?

Copper
Silver
Magnesium
Gold

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