Electrolysis · ⁨Eletrólise⁩

Splitting with electricity

• Electrolysis 电解 uses electricity to break down a molten or aqueous electrolyte 电解质.
• A half-reaction happens at each electrode 电极.
• You can predict the products and calculate amounts.

The two electrodes

• at the cathode 阴极 (negative): positive ions gain electrons (reduction).
• at the anode 阳极 (positive): negative ions lose electrons (oxidation).

A simple cell with a salt bridge and voltmeter

Predicting the products

• a molten electrolyte → metal at the cathode, non-metal at the anode.
• an aqueous one also has water: a reactive metal gives hydrogen instead at the cathode; the anode usually gives oxygen, but a concentrated halide gives the halogen.

A Hofmann voltameter for the electrolysis of water: a power supply drives current through two electrodes, and the gases made at each one collect in the side tubes

Calculations

• the Faraday constant 法拉第常量 $F = Le$ (charge on one mole of electrons). Charge passed $Q = It$.
  1. moles of electrons $= Q / F$.
  2. use the half-equation to find moles of product.
  3. find the mass ($\times M_r$) or gas volume.

A molten electrolyte gives the metal and non-metal; aqueous also has water

You've got it