Electrolysis of Solutions and Getting Reactive Metals Out of Ores · seed 1 · A4, ink-friendly. The answer key prints on its own page for grown-ups.

Solutions, ores and who wins

Science · Matter & Materials · ages 15-16
Name ______________________   Date ____________

  1. Concentrated brine is electrolysed. What forms at the anode?

    • Chlorine
    • Oxygen
    • Hydrogen

  2. Sodium chloride solution is electrolysed. What forms at the cathode?

    • Sodium metal
    • Chlorine gas
    • Hydrogen gas

  3. Iron is extracted with carbon but aluminium needs electrolysis.

    Circle one:   True   False

  4. Why is cryolite added to aluminium oxide?

    • It adds extra aluminium to the melt
    • It lowers the melting point and saves energy
    • It cools the electrodes during the run

  5. Copper sulfate solution is electrolysed. Why does copper form instead of hydrogen?

    • Sulfate ions block the hydrogen
    • Copper is more reactive than hydrogen
    • Copper is less reactive than hydrogen, so it discharges

  6. Why does recycling aluminium use far less energy than extraction?

    • Melting scrap skips mining, refining and electrolysis
    • Recycled aluminium holds no oxide at all
    • Recycling runs at room temperature

  7. Why can carbon free iron but not aluminium from its oxide?

    • Iron ore holds no oxygen at all
    • Carbon burns away before reaching aluminium
    • Aluminium holds its oxygen too tightly for carbon to remove

  8. Sodium sulfate solution is electrolysed. What forms at the anode?

    • Sulfur, since sulfate discharges fully
    • Oxygen, since sulfate is not a concentrated halide
    • Chlorine, since every salt releases it
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Answer key

For grown-ups. Fold this page away before handing over the rest.

Solutions, ores and who wins W1-mt_l-t_JxRR7f-s1

  1. Chlorine · Concentrated halide ions release the halogen instead of oxygen.
  2. Hydrogen gas · Sodium is more reactive than hydrogen, so hydrogen discharges instead.
  3. True · Carbon can shift iron oxide but not aluminium oxide, so aluminium needs electricity.
  4. It lowers the melting point and saves energy · Dissolved oxide melts far cooler, which saves enormous energy.
  5. Copper is less reactive than hydrogen, so it discharges · The less reactive product discharges, and copper sits below hydrogen.
  6. Melting scrap skips mining, refining and electrolysis · Recycling skips every costly step before the melt.
  7. Aluminium holds its oxygen too tightly for carbon to remove · Reactivity decides: carbon outranks iron but not aluminium.
  8. Oxygen, since sulfate is not a concentrated halide · Only concentrated halides beat oxygen, and sulfate is no halide.
Worksheet · LightMySky