electrolysis

• What are electrolytes?

  Ionic compounds that are molten or dissolved in water
• Why are ions in electrolytes free to move?

  Because they are in the molten state or dissolved in water
• What is electrolysis?

  A process where electrical energy breaks down electrolytes
• What type of current is used in electrolysis?

  Direct current (dc)
• What happens to ions during electrolysis?

  They are attracted to oppositely charged electrodes
• What is the negatively charged electrode called in electrolysis?

  Cathode
• What is the positively charged electrode called in electrolysis?

  Anode
• What occurs when ions reach an electrode during electrolysis?

  They gain or lose electrons
• What do positive ions do at the cathode?

  They gain electrons and form atoms
• What do negative ions do at the anode?

  They lose electrons and form atoms
• What happens to Pb2+ ions during the electrolysis of molten lead bromide?

  They gain electrons at the cathode and become Pb atoms
• What happens to Br- ions during the electrolysis of molten lead bromide?

  They lose electrons at the anode and become Br atoms
• What is formed at the negative electrode during the electrolysis of molten calcium chloride?

  Calcium atoms
• What is formed at the positive electrode during the electrolysis of molten calcium chloride?

  Chlorine gas (Cl2)
• What is the key fact about the electrolysis of molten salts?

  A metal forms at the cathode and a non-metal forms at the anode
• Why is water a poor conductor of electricity?

  It contains very few ions
• What happens when water is acidified with dilute sulfuric acid?

  It produces H+ and OH- ions
• What is produced at the cathode during the electrolysis of acidified water?

  Hydrogen gas
• What is produced at the anode during the electrolysis of acidified water?

  Oxygen gas
• What is the overall balanced equation for the electrolysis of water?

  2H2O(l) → 2H2(g) + O2(g)
• How does the volume of hydrogen produced compare to the volume of oxygen during electrolysis of water?

  The volume of hydrogen is twice that of oxygen
• What ions are present in an electrolyte formed by dissolving an ionic compound?

  Hydrogen ions and hydroxide ions from water, and positive and negative ions from the compound
• What determines whether hydrogen or a metal is produced at the cathode?

  The position of the metal in the reactivity series
• What happens at the anode during electrolysis if halide ions are present?

  Halide ions lose electrons and form the corresponding halogen
• What is produced at the anode during the electrolysis of chloride ions?

  Chlorine gas (Cl2)
• What is produced at the anode during the electrolysis of bromide ions?

  Bromine gas (Br2)
• What is produced at the anode during the electrolysis of iodide ions?

  Iodine gas (I2)
• What is produced at the anode during the electrolysis of sulfate ions?

  Oxygen gas (O2)
• What is produced at the anode during the electrolysis of nitrate ions?

  Oxygen gas (O2)
• What are the steps involved in planning an investigation for electrolysis of aqueous solutions?

  • Identify apparatus and setup
  • Choose solutions to test
  • Determine how to test and identify products
  • Consider hazards, risks, and precautions
• What is the purpose of a hypothesis in an investigation?

  To provide an idea to be tested based on scientific knowledge
• What should be done with gases produced during electrolysis?

  They should be collected and tested later
• What is the significance of making careful observations during an experiment?

  To identify patterns and support the original hypothesis
• What should be included in the evaluation of an experiment?

  Reasons for differences in results and improvements to the method
• What is a half equation in electrolysis?

  A representation of the reaction at an electrode showing electron transfer
• What happens to positively charged ions at the cathode?

  They gain electrons
• What happens to negatively charged ions at the anode?

  They lose electrons
• What is the balanced half equation for the formation of aluminium from Al3+?

  $Al^{3+} +$$3e^- → Al$
• What is the balanced half equation for the formation of oxygen from hydroxide ions?

  $4OH^- → 2H_2O +$$O_2 +$$4e^-$
• What is oxidation in terms of electrons?

  Oxidation is the loss of electrons