Electrolysis Pt:3

• What is electrolysis used for?

  To split compounds into their elements
• How is electrolysis performed?

  By passing an electric current through an electrolyte
• What must happen to ions in an electrolyte for electrolysis to work?

  The ions must be free to move around
• What must be done to insoluble compounds for electrolysis?

  They must be melted to make them a molten liquid
• How can soluble compounds be prepared for electrolysis?

  By dissolving them in water
• What equipment is needed for an electrolysis experiment?

  • A beaker full of electrolyte
  • Two electrodes (anode and cathode)
  • A wire connecting the electrodes
  • A power supply
• What is the main difficulty in the electrolysis of aqueous solutions?

  Determining which ions will go to each electrode
• What ions are present in aqueous solutions besides those from the ionic compound?

  Hydrogen ions and hydroxide ions from water
• Which ions does the cathode attract?

  The cathode attracts positive ions
• What determines which ion is discharged at the cathode?

  The ion of the least reactive element is discharged
• What happens if copper ions are present at the cathode?

  Copper ions will be discharged because they are less reactive than hydrogen ions
• What is discharged at the anode if halides are present?

  The halide ions will be discharged
• What is discharged at the anode if no halides are present?

  The hydroxide ions will be discharged
• What ions are present in an aqueous solution of copper sulfate?

  Copper 2 plus ions and sulfate 2 minus ions
• What happens at the cathode during the electrolysis of copper sulfate?

  Copper ions gain electrons and form pure copper
• What is the result of hydroxide ions discharging at the anode?

  They form oxygen and water
• What is the equation for the reaction of hydroxide ions at the anode?

  4 OH⁻ → 2 H₂O + O₂ + 4 e⁻
• What ions are present in an aqueous solution of sodium chloride?

  Sodium ions, chloride ions, hydrogen ions, and hydroxide ions
• What happens at the cathode during the electrolysis of sodium chloride?

  Hydrogen ions are discharged to form hydrogen gas
• What happens at the anode during the electrolysis of sodium chloride?

  Chloride ions are discharged to form chlorine gas
• What are the key rules for discharging ions during electrolysis?

  • At the cathode, the least reactive positive ion is discharged.
  • At the anode, if halides are present, they are discharged; otherwise, hydroxide ions are discharged.