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Electrolysis of aqueous solutions and practicals

Chemical changes • Electrolysis

Key concepts

What you'll likely be quizzed about

  • Electrolysis uses a direct current source connected to two electrodes immersed in an electrolyte.
  • The cathode, the negative electrode, attracts positive ions (cations).
  • The anode, the positive electrode, attracts negative ions (anions).
  • The electrolyte contains mobile ions that carry charge through the solution.
  • Choosing the right electrode material impacts observed chemistry.
  • Inert electrodes, like graphite or platinum, remain unchanged chemically, allowing observation of the electrolyte's reactions only.
  • Reactive electrodes can supply or remove metal atoms, changing the overall products.

Flashcards

Test your knowledge with interactive flashcards

How does electrode material affect electrolysis results?

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Reactive electrodes can dissolve or produce extra ions, altering products; inert electrodes display only reactions of the electrolyte.

Key notes

Important points to keep in mind

Cathode is negative and reduces cations; anode is positive and oxidizes anions.

Inert electrodes (graphite or platinum) stop electrode material from changing the chemistry.

At the cathode, metal deposition occurs if the metal ion is less reactive than hydrogen; otherwise hydrogen gas forms.

At the anode, halide ions produce halogen gases; absent halides, water or hydroxide oxidizes to oxygen.

Half-equations illustrate electron transfer and balance electrode reactions.

Gas tests: 'pop' for hydrogen, glowing splint relights for oxygen, bleaching indicates chlorine.

Concentration, electrode material, current density, and overpotential influence which species discharges.

Common practical errors include gas loss, impurities in solutions, and incorrect electrode polarity.

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