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Learn5070Paper 1 · Multiple ChoiceElectrochemistryElectroplating and fuel cells
Electrochemistry · Subtopic 2 of 2

Electroplating and Fuel Cells

In electroplating, the object to be coated is the cathode, the plating metal is the anode, and the electrolyte contains ions of the plating metal. Copper is purified the same way: an impure copper anode dissolves and pure copper deposits on the cathode. A hydrogen–oxygen fuel cell combines hydrogen and oxygen to produce electricity directly, with water as the only product.

Cambridge 5070 Paper 1Cambridge 5070 Paper 2Cambridge 0620 Papers 2, 4Cambridge 0620 Papers 1, 3≈ 30 minRevision 1 · updated 2026-10-30
Section 1 of 14

Learning objectives

  • Set up an electroplating cell.
  • Explain how copper is purified by electrolysis.
  • Describe the hydrogen–oxygen fuel cell and compare it with petrol engines.
Pause and think

Cheap jewellery looks golden but turns green after a few months. Why?

Section 2 of 14

Core idea

Start hereSilver spoons that aren't

Many "silver" spoons are steel with a coating of silver thinner than a hair. Electrolysis built that coating one atom at a time.

The big idea

Put the object to be coated at the cathode, the coating metal at the anode, and use a solution of the coating metal's ions. A fuel cell runs electrolysis "in reverse", combining hydrogen and oxygen to make electricity.

1. Electroplating

Electroplating a key with copper

Copper moves from anode to key through the solution.

Worked exampleChromium plating

A steel bumper is chromium-plated.

Goal
Set-up and reasons.
Strategy
Object at cathode; electrolyte contains Cr3+\mathrm{Cr^{3+}}.
  1. cathode: bumper\text{cathode: bumper}
    Chromium ions are attracted to it.
  2. Cr3++3e−→Cr\mathrm{Cr^{3+}}+3e^-\rightarrow\mathrm{Cr}
    Reduction deposits chromium.
AnswerShiny, hard-wearing, corrosion-resistant surface.
✓ CheckSteel underneath gives strength; chromium gives protection ✓.

2. Fuel cells

Hydrogen and oxygen are fed to separate electrodes. Hydrogen loses electrons, which flow through an external circuit as an electric current, and oxygen gains them. The overall reaction is 2H2+O2→2H2O\mathrm{2H_2+O_2\rightarrow2H_2O}.

Exam tipFuel cells vs petrol engines Advantages: only water produced; more efficient; quiet. Disadvantages: hydrogen storage is difficult and flammable; hydrogen is often made from fossil fuels; few refuelling stations.
Pause and think

Is a fuel-cell car "zero-emission"?

Summary

  • Object = cathode.
  • Purify copper: impure anode, pure cathode.
  • Fuel cell: water only.
Key words
Electroplating
Coating an object with a metal by electrolysis.
Fuel cell
Converts chemical energy of a fuel directly into electricity.
Anode sludge
Impurities that fall from the anode during purification.
HistoryApollo. The Apollo spacecraft that took astronauts to the Moon were powered by hydrogen–oxygen fuel cells, and the crew drank the water they produced.
Fun factOlympic gold. Olympic gold medals are mostly silver, plated with about 6 g of gold.
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