Aqueous Solutions

• 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 for electrolysis to work?

  Ions in the electrolyte must be free to move
• What must be done to insoluble compounds for electrolysis?

  They must be melted into a molten liquid
• How do you prepare soluble compounds for electrolysis?

  Dissolve them in water to make electrolyte
• What equipment is needed for an electrolysis experiment?

  • Beaker full of electrolyte
  • Two electrodes (anode and cathode)
  • Wire connecting electrodes
  • Power supply
• What is the main difficulty in electrolysis of aqueous solutions?

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

  Hydrogen ions and hydroxide ions from water
• What does the cathode attract during electrolysis?

  Positive ions from the electrolyte
• What is the rule for discharging ions at the cathode?

  The least reactive ion will be discharged
• What happens if copper ions are present at the cathode?

  Copper ions will be discharged instead of hydrogen
• What happens at the anode during electrolysis?

  Negative ions are discharged to form oxygen or halides
• 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?

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

  Copper 2+ and sulfate 2- ions
• What ions does the cathode discharge in copper sulfate solution?

  Copper ions are discharged over hydrogen ions
• What is formed at the cathode during copper sulfate electrolysis?

  Pure copper accumulates around the cathode
• What do hydroxide ions form at the anode during copper sulfate electrolysis?

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

  4 $OH^-$ → 2 $H_2O$ + $O_2$ + 4 electrons
• What ions are present in an aqueous solution of sodium chloride?

  Sodium ions and chloride ions
• Which ions does the cathode discharge in sodium chloride solution?

  Hydrogen ions are discharged over sodium ions
• What is formed at the cathode during sodium chloride electrolysis?

  Hydrogen gas is formed
• What is discharged at the anode during sodium chloride electrolysis?

  Chloride ions are discharged to form chlorine gas
• What resources are available for further study on electrolysis?

  • Videos on the website Cognito
  • Access to questions and past papers
  • Progress tracking for study