Metal Properties and Reactivity: Practice Questions

These are original questions written for Marlbridge, in the style and at the standard of the examination. They are not reproduced past-paper questions — examination boards hold copyright in their own papers. Use these alongside the official past papers available free from your board.

Related: Metal Properties and Reactivity revision notes

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Section A

1. List these metals in order of decreasing reactivity: copper, calcium, zinc, potassium, iron. [2]

2. State what you would observe when sodium, calcium and copper are each added to cold water. [3]

Section B

3. Explain how the reactivity of a metal determines its method of extraction, referring to two methods. [4]

4. (Extension beyond this resource’s core scope — blast-furnace extraction detail is covered in Alloys and Extraction of Metals ; included here only as a worked example of question 3’s reactivity-extraction link.) Iron is extracted in the blast furnace.

(a) Write the equation for the reduction of iron(III) oxide by carbon monoxide. [2] (b) Explain the role of limestone. [3] (c) Explain why aluminium cannot be extracted this way. [2]

5. Rusting requires both air and water.

(a) Describe an experiment to show that both are needed. [4] (b) Explain how galvanising protects iron by two different mechanisms. [4]

6. (Extension beyond this resource’s core scope — alloys are covered in Alloys and Extraction of Metals .) Explain, using a diagram in words, why an alloy is harder than the pure metal. [3]

7. Magnesium ribbon reacts rapidly with steam, but only very slowly with cold water.

(a) Write the word equation for magnesium’s reaction with steam. [1] (b) State why the same metal can react at very different rates with water and with steam. [1]

8. In an experiment, magnesium reacts vigorously with dilute hydrochloric acid, zinc reacts moderately, and silver shows no reaction at all.

(a) Rank the three metals in order of decreasing reactivity, with reasoning. [2] (b) State which of the three would react with dilute acid to release hydrogen gas, and which would not. [2]

9. Painting, greasing and galvanising can all be used to protect iron from rusting.

(a) Explain why painting and greasing work, and state one limitation they share. [2] (b) Explain why galvanising still protects iron even where the coating is scratched, unlike painting or greasing. [2]

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Answers

1. Potassium, calcium, zinc, iron, copper [2 — 1 mark if one pair is transposed].

2. Sodium — melts into a ball, fizzes vigorously and moves rapidly on the surface, may ignite [1]. Calcium — steady stream of bubbles, sinks then rises, solution turns cloudy [1]. Copper — no reaction [1].

3. A metal more reactive than carbon must be extracted by electrolysis of its molten ore, because carbon cannot reduce it [1] [1]. A metal less reactive than carbon can be reduced by heating with carbon, which is much cheaper [1]; the least reactive metals such as gold occur native and need no extraction [1].

4. (a) Fe₂O₃ + 3CO → 2Fe + 3CO₂ [1], correctly balanced [1]. (b) The limestone decomposes to calcium oxide and carbon dioxide in the heat [1]; the calcium oxide is basic and reacts with the acidic silicon dioxide impurity [1] to form calcium silicate — molten slag, which floats on the iron and is drained off [1].

(c) Aluminium is more reactive than carbon [1], so carbon cannot remove the oxygen from aluminium oxide — electrolysis is required instead [1].

5. (a) Set up three boiling tubes each with an iron nail [1]. Tube 1: air and water — the nail rusts [1]. Tube 2: boiled water with a layer of oil on top, excluding air — no rust [1]. Tube 3: dry air with anhydrous calcium chloride and a bung — no rust [1]. Only the tube with both air and water shows rusting. (b) The zinc layer physically covers the iron, keeping out air and water — a barrier [1] [1]. Zinc is more reactive than iron, so even if the coating is scratched the zinc is oxidised in preference [1] — sacrificial protection, which continues to protect the exposed iron [1].

6. In a pure metal the atoms are the same size and arranged in regular layers that can slide over one another [1]. In an alloy, atoms of a different size are introduced [1], which distorts the layers and prevents them sliding, so the alloy is harder [1].

7. (a) magnesium + steam → magnesium oxide + hydrogen [1]. (b) Steam supplies more energy (a higher temperature) than cold water, which is enough to overcome magnesium’s activation energy for reaction, whereas cold water alone is not [1].

8. (a) Magnesium > zinc > silver [1]; a more vigorous reaction with the same acid under the same conditions indicates a more reactive metal [1]. (b) Magnesium and zinc would react to release hydrogen gas [1]; silver, being below hydrogen in the reactivity series, would not react at all [1].

9. (a) Both physically exclude oxygen and water from the metal surface, stopping rusting while the coating remains intact [1]; the shared limitation is that once the coating is scratched or damaged, the exposed metal beneath rusts normally [1]. (b) Zinc is more reactive than iron, so where the coating is broken, the zinc corrodes preferentially (sacrificial protection), continuing to protect the iron even without an intact barrier [1] — a mechanism painting and greasing simply don’t have, since neither coating material is more reactive than iron [1].

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Where marks are usually lost

• Saying copper reacts slowly with water.
• Omitting the decomposition step for limestone.
• Giving only the barrier explanation for galvanising.
• Saying alloys are harder because the atoms bond more strongly.
• Treating “reacts with water” and “reacts with steam” as the same test — steam supplies more energy, so a metal that barely reacts with cold water can react rapidly with steam.
• Assuming any protective coating gives sacrificial protection — only a coating metal more reactive than iron (such as zinc) does; paint and grease are barrier methods only.