Key Concepts: Metals are ordered by their reactivity with water, dilute acids and by displacement reactions. Order (most → least reactive): K, Na, Li, Ca, Mg, Al, Zn, Fe, Cu, Ag, Au. Rusting requires both water and oxygen. Oxidation = gain of oxygen or loss of electrons; reduction = loss of oxygen or gain of electrons.
Section A — Building the Reactivity Series
1. Three metals are tested with cold water and dilute acid. Use the observations to rank them most → least reactive. [3]
| Metal | With cold water | With dilute acid |
|---|
| X | Vigorous reaction | Very vigorous |
| Y | No reaction | Slow reaction |
| Z | No reaction | No reaction |
2. Write the order of reactivity for the following metals, most reactive first: Na, Cu, Mg, Fe, K, Zn, Ag. [2]
3. Explain how displacement reactions can be used to establish the order of metals in the reactivity series. Give an example. [3]
Section B — Displacement Reactions and Equations
4. Will zinc displace copper from copper(II) sulfate solution? Explain briefly. [2]
5. Write balanced symbol equations for the following. [4]
a) Magnesium reacting with dilute hydrochloric acid
b) Zinc reacting with copper(II) sulfate solution
c) Iron reacting with dilute sulfuric acid
d) Calcium reacting with cold water
Section C — Rusting
6. State the two conditions required for iron to rust. [2]
7. Describe an experiment using three sealed test tubes containing iron nails to prove that both conditions from Question 6 are needed for rusting. [3]
8. State three methods of preventing rusting and explain briefly how each works. [3]
Section D — Oxidation and Reduction
9. Define oxidation and reduction in terms of (a) oxygen transfer and (b) electron transfer. [4]
10. In the reaction: Fe₂O₃ + 3CO → 2Fe + 3CO₂ [3]
a) Which substance is oxidised? Explain.
b) Which substance is the reducing agent?
c) Which substance is the oxidising agent?
Total marks: 29
Mark Scheme
1. X most reactive, Y middle, Z least reactive [3]
2. K, Na, Mg, Zn, Fe, Cu, Ag [2]
3. Add a more reactive metal to a solution of a less reactive metal's salt; if displacement occurs (colour change, temperature rise), the added metal is more reactive; example: iron added to copper sulfate — solution turns from blue to colourless and copper deposits on iron [3]
4. Yes; zinc is more reactive than copper so it displaces copper from the solution [2]
5. a) Mg + 2HCl → MgCl₂ + H₂ b) Zn + CuSO₄ → ZnSO₄ + Cu c) Fe + H₂SO₄ → FeSO₄ + H₂ d) Ca + 2H₂O → Ca(OH)₂ + H₂ [4]
6. Water (moisture) and oxygen [2]
7. Tube 1: nail + dry air only (calcium chloride to absorb water) — no rust; Tube 2: nail + boiled water (no dissolved air) + oil layer — no rust; Tube 3: nail + water + air — rust forms; comparison shows both are needed [3]
8. Any three: painting — physical barrier prevents contact with air/water; galvanising/zinc coating — zinc acts as sacrificial metal; oil/grease — barrier; sacrificial protection — reactive metal (e.g. Mg) corrodes instead of iron [3]
9. a) Oxidation = gain of oxygen; reduction = loss of oxygen; b) Oxidation = loss of electrons; reduction = gain of electrons [4]
10. a) CO is oxidised — it gains oxygen to form CO₂; b) Reducing agent: CO; c) Oxidising agent: Fe₂O₃ [3]