Electrolysis

• What is the main topic of this unit?

  Electrolysis
• What are electrolytes?

  Substances that produce ions when dissolved in water
• What is the source of ions in molten ionic compounds during electrolysis?

  There is only one source of ions
• How does electrolysis of aqueous solutions differ from molten ionic compounds?

  Aqueous solutions are more complicated due to the presence of water molecules
• What ions are produced from water in aqueous solutions?

  H⁺ and OH⁻ ions
• What happens if the metal is more reactive than hydrogen during electrolysis?

  Hydrogen ions (H⁺) will be produced
• What occurs if a less reactive metal is present during electrolysis?

  Hydrogen gas will be produced instead
• What happens when halide ions are present during electrolysis?

  Molecules of the halogen gas will be formed
• What is produced if no halide ions are present during electrolysis?

  Oxygen gas is formed from the hydroxide ions
• What ions are present in a solution of sodium chloride (NaCl)?

  Na⁺, Cl⁻, OH⁻, and H⁺
• What is produced at the cathode when sodium chloride is electrolyzed?

  Hydrogen gas is produced
• Write the half-equation for the reaction occurring at the cathode during the electrolysis of sodium chloride.

  2H⁺ + 2e⁻ → H₂
• What is produced at the anode when sodium chloride is electrolyzed?

  Chlorine gas is produced
• Write the half-equation for the reaction occurring at the anode during the electrolysis of sodium chloride.

  2Cl⁻ → Cl₂ + 2e⁻
• How can you test for chlorine gas in the lab?

  Chlorine bleaches damp litmus paper, turning it white
• What sound does hydrogen make when burnt?

  A “squeaky pop” sound
• What happens when hydrogen is burned with a lighted solid?

  It can make a temporary fog
• What is the process of electrolysis in an aqueous solution of copper bromide (CuBr₂) using inert electrodes?

  • Copper bromide dissociates into Cu²⁺ and Br⁻ ions.
  • At the cathode, Cu²⁺ ions gain electrons to form copper metal.
  • At the anode, Br⁻ ions lose electrons to form bromine gas.
• What is the ionic equation for the reaction occurring at the anode during the electrolysis of copper bromide?

  Br⁻ → ½Br₂ + e⁻