Electrolysis

• What is electrolysis of molten salts?

  It is a process where electrical energy breaks down electrolytes in molten state.
• What are electrolytes?

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

  Because they are in a molten state or dissolved in water.
• What is the role of direct current (dc) in electrolysis?

  It provides the electrical energy needed to break down electrolytes.
• What is the negatively charged electrode called in electrolysis?

  The negatively charged electrode is called the cathode.
• What happens to positively charged ions during electrolysis?

  They move towards the cathode.
• What is the positively charged electrode called in electrolysis?

  The positively charged electrode is called the anode.
• What occurs when ions reach an electrode during electrolysis?

  They gain or lose electrons, forming atoms or molecules of elements.
• What happens to Pb$^{2+}$ ions during the electrolysis of molten lead bromide?


  They gain electrons at the cathode and become Pb atoms.
• What do Br$^{-}$ ions do during the electrolysis of molten lead bromide?


  They lose electrons at the anode and become Br atoms, which form Br$_{2}$ molecules.
• What is formed at the negative electrode during the electrolysis of molten salts?

  A metal forms at the cathode.
• What is formed at the positive electrode during the electrolysis of molten salts?

  A non-metal forms at the anode.
• What are the products of electrolysis of molten calcium chloride?

  Calcium is formed at the negative electrode and chlorine gas at the positive electrode.
• Why is water a poor conductor of electricity?

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

  It produces H$^{+}$ and OH$^{-}$ ions.
• What gas is formed at the cathode during the electrolysis of acidified water?

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

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

  2H$_{2}O(l) \rightarrow 2H<latex>_{2}(g) +$$O<latex>_{2}(g)$</latex>
• How does the volume of hydrogen produced compare to 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?

  It contains hydrogen ions and positive ions from the compound, as well as hydroxide ions and negative ions from the compound.
• What determines whether hydrogen or a metal is produced at the cathode during electrolysis of solutions?

  It depends on the reactivity of the metal compared to hydrogen.
• What is produced at the anode during electrolysis unless halide ions are present?

  Oxygen is produced from hydroxide ions.
• What are the products formed at the anode during the electrolysis of different electrolytes in solution?

  • Chloride (Cl$^{-}$): Chlorine (Cl$_{2}$)
  • Bromide (Br$^{-}$): Bromine (Br$_{2}$)
  • Iodide (I$^{-}$): Iodine (I$_{2}$)
  • Sulfate (SO$_{4}^{2-}$): Oxygen (O$_{2}$)
  • Nitrate (NO$_{3}^{-}$): Oxygen (O$_{2}$)
• What is a half equation in electrolysis?

  A half equation represents the reaction at an electrode showing electron gain or loss.
• What happens to positively charged ions at the cathode?

  They gain electrons.
• Write the half equation for the formation of sodium at the cathode.

  Na$^{+} +$$e^{-} \rightarrow Na$
• Write the balanced half equation for the formation of aluminium during electrolysis.

  Al$^{3+} +$$3e^{-} \rightarrow Al$
• Write the half equation for the formation of chlorine at the anode.

  2Cl$^{-} \rightarrow Cl<latex>_{2} +$$2e^{-}$
• Write the balanced half equation for the formation of oxygen from hydroxide ions.

  4OH$^{-} \rightarrow 2H<latex>_{2}O +$$O<latex>_{2} +$$4e^{-}$
• What is oxidation in terms of electrons?

  Oxidation is the loss of electrons.
• What is reduction in terms of electrons?

  Reduction is the gain of electrons.
• Where does reduction occur during electrolysis?

  Reduction occurs at the cathode.
• Where does oxidation occur during electrolysis?

  Oxidation occurs at the anode.
• What does OIL RIG stand for in electrolysis?

  Oxidation Is Loss of electrons, Reduction Is Gain of electrons.
• What are the hazards and precautions associated with electrolysis experiments?

  • Copper sulfate solution: Causes skin irritation (wear gloves)
  • Copper sulfate solution: Causes serious eye irritation (wear eye protection)
  • DC electricity supply: Risk of electric shock (ensure electrodes do not touch and switch off before handling)
• What should be included in a results table for electrolysis observations?

  Electrolyte, observations at positive electrode, and observations at negative electrode.
• Why is it important to analyze the results of an electrolysis experiment?

  To identify patterns and determine if they support the original hypothesis.
• What should be addressed in the evaluation of an electrolysis practical?

  Results agreement with predictions, actions for accuracy, and possible improvements.