in aqueous solution

• Aqueous solution


  Contains the compound and water
• Aqueous ionic electrolyte


  Has more than one positive and negative ions respectively
• Sodium chloride aqueous solution

  Hydroxide ions from the ionisation of water and chloride ions from dissociation of ions are present as anions. Hydrogen ions from the ionisation of water and sodium ions from the dissociation of ions are then present as cations
• Aqueous solution


  Only one cation and one anion gets preferentially discharged. This is known as selective discharge of ions
• Selective discharge of ions with inert electrodes

  1. Selective discharge of cations

  2. Selective discharge of anions

  3. Effect of concentration on selective discharge of anions
• Selective discharge of cations


  • Based on the reactivity series. The more reactive the metal, the higher tendency to form ions. Ions of reactive metals such as sodium and potassium will remain as ions and will not be discharged, remaining in the solution. Ions of hydrogen and less reactive metals such as copper and silver will gain electrons more readily and get discharged.
• Hydrogen ion as a reference point


  Hydrogen ions are preferentially discharged to ions above it while ions below hydrogen ions are discharged
• Selective discharge of anions


  • Sulfate ions and nitrate ions remain in the solution and will not be discharged. Hydroxide ions give up electrons most readily to form water and oxygen, hydroxide ion is the most readily discharged
• Effect of concentration on selective discharge of anions


  • A halide anion in high concentration is more readily discharged. Halide ions in dilute aqueous electrolyte will not be discharged while halide ions in concentrated electrolyte will be readily discharged.