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Batteries, Fuel Cells and Corrosion: Flashcards

Revise primary and rechargeable batteries, fuel cells, how iron rusts and how corrosion is prevented.

10 cardsIntermediate

10 cards

  1. Question
    What is a battery, in electrochemical terms?
    Answer

    One or more galvanic cells: a spontaneous redox reaction drives electrons through a circuit.

  2. Question
    What is the difference between a primary and a secondary battery?
    Answer

    Primary: used once. Secondary: rechargeable, by driving the reaction backwards with an external current (electrolysis).

  3. Question
    In a battery, which electrode is negative?
    Answer

    The anode (oxidation); the cathode is positive.

  4. Question
    What moves between the electrodes in a lithium-ion battery?
    Answer

    Li⁺ ions, between the graphite anode and the metal-oxide cathode.

  5. Question
    Give the overall reaction and E° of a hydrogen fuel cell.
    Answer

    2H₂ + O₂ → 2H₂O; E° = 1.23 V.

  6. Question
    What two substances are needed for iron to rust?
    Answer

    Oxygen and water.

  7. Question
    Give the anode half-equation for rusting.
    Answer

    Fe→FeX2++2 eX−\ce{Fe -> Fe^2+ + 2e-}

  8. Question
    Why does salt speed up rusting?
    Answer

    It makes the water a better electrolyte, so ions move more easily.

  9. Question
    Why does zinc protect iron even when the coating is scratched?
    Answer

    Zinc (E° −0.76 V) is more easily oxidized than iron (−0.44 V), so it corrodes instead (sacrificial protection).

  10. Question
    How many coulombs is 2000 mAh?
    Answer

    2.000 A × 3600 s = 7200 C