Electrolysis of Aqueous Solution

Components of an Aqueous Solution

• Ions in Water

• Electrolytes are aqueous or molten.

  • In order for electrolysis to occur, compound must be dissolved in water, or melted to form a liquid.
  • This means that the ions are free to move around when a current is applied.

• Aqueous electrolytes contain water.

  • When a compound is dissolved in water, the resulting solution has water present.
  • This means that there is both the ionic compound and water molecules in the solution.

• Water splits into ions.

  • Water molecules can split into two ions: hydrogen ions (H+) and hydroxide ions (OH–). When joined together, they produce water molecules, H2O.

Ion Production with Aqueous Electrolytes

• When aqueous electrolytes are involved, electrolysis is slightly more complicated.

• Two ions are attracted to the cathode.

  • The hydrogen ion and the metal ion are attracted to the cathode. To decide what substance is made at the cathode, we must use the reactivity series.

• Metal reactivity is compared to hydrogen.

  • If the metal element formed during electrolysis is more reactive than hydrogen, then hydrogen will be produced at the cathode.
  • If the metal element formed is less reactive than hydrogen, then the metal is produced at the cathode.

• Two ions are attracted to the anode.

  • The hydroxide ions and halide ions are attracted to the anode.
  • If both are present, then a halogen is formed. If no halide ions are present, then the hydroxide ions are  discharged, and oxygen is formed.