electrolysis of solutions

• What is electrolysis used for?

  To split compounds into their elements
• How does electrolysis work?

  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?

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

  Dissolve them in water
• 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 metal ions are present at the cathode?

  Hydrogen ions will be discharged if less reactive
• What happens if copper ions are present at the cathode?

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

  Negative ions from the compound and hydroxide ions
• What is the rule for discharging ions at the anode?

  Halide ions are discharged if present
• What happens if no halide ions are present at the anode?

  Hydroxide ions will be discharged
• What ions are produced from an aqueous solution of copper sulfate?

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

  Copper ions gain electrons and form copper
• What is formed at the cathode during copper sulfate electrolysis?

  Pure copper accumulates around the cathode
• What is discharged at the anode during copper sulfate electrolysis?

  Hydroxide ions are discharged
• What do hydroxide ions form at the anode?

  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, hydroxide ions
• What happens at the cathode during sodium chloride electrolysis?

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

  Chloride ions are discharged
• What gas is formed at the anode during sodium chloride electrolysis?

  Chlorine gas
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