C6 - Electrolysis

• What is the function of the anode in electrolysis?

  It is the positive electrode.
• What does electrolysis do to a substance?

  It breaks down a substance using electricity.
• Under what conditions can ionic compounds be electrolyzed?

  When they are molten or dissolved in water.
• Why can ionic compounds only be electrolyzed when molten or dissolved?

  Because their ions are free to move.
• Which ions move to the cathode during electrolysis?

  Positive ions.
• Which ions move to the anode during electrolysis?

  Negative ions.
• What happens to positive ions at the cathode?

  They gain electrons and are reduced.
• What happens to negative ions at the anode?

  They lose electrons and are oxidized.
• What can be produced at the anode during electrolysis in aqueous solution?

  Oxygen gas or a halogen.
• What is usually produced at the cathode during electrolysis in aqueous solution?

  The less reactive element, hydrogen or metal.
• What is the source of aluminium oxide used in extraction?

  Bauxite ore.
• Why is aluminium oxide mixed with molten cryolite?

  To lower its melting point and reduce energy.
• Where does aluminium form during electrolysis?

  At the cathode (negative electrode).
• Where does oxygen form during electrolysis?

  At the anode (positive electrode).
• Why are carbon anodes replaced regularly during electrolysis?

  They burn away as oxygen reacts with them.
• What are the products of electrolyzing sodium chloride solution (brine)?

  Chlorine gas, hydrogen gas, and sodium hydroxide.
• Where is hydrogen produced during the electrolysis of brine?

  At the cathode (-).
• Where is chlorine produced during the electrolysis of brine?

  At the anode (+).
• Which ions are discharged at the cathode during brine electrolysis?

  H⁺(aq) ions.
• Which ions are discharged at the anode during brine electrolysis?

  Cl^-(aq) ions.
• How does the electrolysis of brine differ from other electrolytic processes?

  It produces chlorine gas and sodium hydroxide.
• What is the role of hydroxide ions in the electrolysis of brine?

  They are discharged at the anode if chlorine is not present.