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Electrolysis: Flashcards

Revise electrolytic cells, electrode products in molten and aqueous electrolytes, industrial electrolysis and Faraday's law.

10 cardsIntermediate

10 cards

  1. Question
    What is electrolysis?
    Answer

    Using electricity to drive a non-spontaneous redox reaction.

  2. Question
    Signs and reactions at the electrodes in electrolysis?
    Answer

    Anode (+): oxidation. Cathode (−): reduction.

  3. Question
    Products of electrolysing molten NaCl?
    Answer

    Sodium at the cathode, chlorine at the anode.

  4. Question
    When does a metal NOT form at the cathode in aqueous solution?
    Answer

    When the metal is more reactive than hydrogen (e.g. Na, K, Mg, Al): water is reduced to H₂ instead.

  5. Question
    What forms at the anode in aqueous solution?
    Answer

    The halogen from a concentrated halide; otherwise oxygen (e.g. with sulfate or nitrate).

  6. Question
    Products of electrolysing concentrated brine?
    Answer

    Chlorine (anode), hydrogen (cathode) and sodium hydroxide (left in solution).

  7. Question
    How is aluminium extracted?
    Answer

    Electrolysis of Al₂O₃ dissolved in molten cryolite (about 950 °C); Al³⁺ + 3e⁻ → Al; carbon anodes burn away.

  8. Question
    How is copper purified?
    Answer

    Impure copper anode dissolves; pure copper deposits on the cathode; impurities fall as anode sludge.

  9. Question
    Faraday's-law steps?
    Answer

    Q = It; n(e⁻) = Q ÷ F (F = 96 485 C/mol); use the half-equation ratio; then mass or volume.

  10. Question
    Moles of electrons per mole of Ag, Cu, Al and Cl₂?
    Answer

    Ag 1, Cu 2, Al 3, Cl₂ 2.