Aqueous Solutions

• In the electrolysis of a solution, which two ions are present from the water molecules themselves?

  H⁺ ions and OH⁻ ions
• In the electrolysis of aqueous solutions, what is the rule for determining which ion will be oxidised (lose electrons) at the anode (positive electrode)

  It will always be the OH⁻, unless there is a halide ion (such as Cl⁻, or Br⁻) present
• In the electrolysis of aqueous solutions, what is the rule for determining which ion will be reduced (gain electrons) at the cathode (negative electrode)?

  It will always be the H⁺ ion, unless Cu²⁺ is present (another way of phrasing it would be that it is always the ion of the least reactive element).
• In the electrolysis of aqueous sodium chloride KBr (aq), which 4 ions would be present in the electrolyte?

  1. Potassium ions (K⁺)
  2. Bromide ions (Br⁻)
  3. Hydrogen ions(H⁺)
  4. Hydroxide ions(OH⁻)
• In the electrolysis of aqueous sodium chloride, KBr (aq), which of the ions will be oxidised (lose electrons) at the anode (positive electrode)?

  Bromide ions (Br⁻)
• In the electrolysis of aqueous sodium chloride, NaCl(aq), which ions will be reduced at the cathode (negative electrode)?

  Hydrogen ions (H⁺)
• Why is aqueous electrolysis generally cheaper than molten electrolysis?


  In aqueous electrolysis the substance is just dissolved in water, no energy is required to melt it