4.3.4 Electrolysis of Aqueous Solutions

• What form do electrolytes come in?

  Molten or solution.
• What do you find in a molten electrolyte?

  1 positive ion and 1 negative ion.
• What forms on the anode?

  Non-metal ions.
• Where do the non-metal ions go to?

  The anode.
• What is an anode?

  A positive electrode.
• What is a cathode?

  A negative electrode.
• Where do the metal ions go to?

  The cathode.
• What forms on the cathode?

  Metal ions.
• What are ions that form on the anode called?

  Anions.
• What are ions that form on the cathode called?

  Cations.
• What charge do the metal ions have?

  Positive charge.
• What charge do the non-metal ions have?

  Negative charge.
• What two positive ions form at the cathode?

  Hydrogen and metal ions.
• When is hydrogen formed at the cathode?

  When a metal more reactive than hydrogen is there.
• What two negative ions form at the anode?

  Non-metal and hydroxide ions.
• When is oxygen formed at the anode?

  When there is a complex ion.
• Why do electrodes need high melting points and to be inert?

  So they don’t react with the reactants or products.
• What does HCl produce at the anode?

  Chlorine.
• What does HCl produce at the cathode?

  Hydrogen.
• What does NaCl produce at the anode?

  Chlorine.
• What does NaCl produce at the cathode?

  Hydrogen.
• What does potassium chloride produce at the cathode?

  Hydrogen.
• What does copper sulfate produce at the cathode?

  Copper.
• What does sodium bromide produce at the cathode?

  Hydrogen.
• What does zinc chloride produce at the cathode?

  Hydrogen.
• What does silver nitrate produce at the cathode?

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

  H+ and OH-.
• 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, NaCl (aq), which four ions would be present in the electrolyte?

  Sodium ions (Na+)

  Chloride ions (Cl-)

  Hydrogen ions (H+)

  Hydroxide ions (OH-)
• In the electrolysis of aqueous sodium chloride, NaCl (aq), which of the four ions will be oxidised at the anode (positive electrode)?

  Chloride ions (Cl-).
• In the electrolysis of aqueous sodium chloride, NaCl (aq), which of the four ions will be reduced at the cathode (negative electrode)?

  Hydrogen ions (H+).
• In the electrolysis of aqueous copper nitrate, Cu(NO3)2 (aq), which four ions would be present in the electrolyte?

  Copper ions (Cu2+)

  Nitrate ions (NO3-)

  Hydrogen ions (H+)

  Hydroxide ions (OH-)
• In the electrolysis of aqueous copper nitrate, Cu(NO3)2 (aq), which of the four ions will be oxidised at the anode (positive electrode)?


  Hydroxide ions (OH-).
• In the electrolysis of aqueous copper nitrate, Cu(NO3)2 (aq), which of the four ions will be reduced at the cathode (negative electrode)?

  Copper ions (Cu2+).