Electrolysis and Electroplating Quiz

Electrolytes and Non-Electrolytes

• Electrolytes are substances that conduct electricity when dissolved in water or molten.
• Non-electrolytes do not conduct electricity when dissolved in water or molten.
• Examples of electrolytes include acids, bases, and salts (e.g., NaCl, CuSO4).
• Examples of non-electrolytes include alcohol, sugar, and some organic compounds.
• Strong electrolytes dissociate completely into ions in solution.
• Weak electrolytes dissociate partially.

Electrolysis

• Electrolysis is the decomposition of a chemical compound (electrolyte) by passing a direct electric current through it.
• It involves the discharge of ions at the electrodes.
• At the cathode (negative electrode), cations gain electrons (reduction).
• At the anode (positive electrode), anions lose electrons (oxidation).
• The process is a redox reaction (oxidation and reduction).

Electrolytic Cells

• Electrolytic cells are devices used for electrolysis.
• They contain electrodes (anode and cathode) immersed in an electrolyte solution.
• Electrodes are usually made of metal or graphite.
• The cell is connected to a battery to supply the direct current.

Electrode Reactions

• Oxidation occurs at the anode, where anions lose electrons, forming neutral atoms or molecules.
• Reduction occurs at the cathode, where cations gain electrons, forming neutral atoms or molecules.
• The nature of the electrodes and the concentration of ions in the electrolyte influence the discharge of ions.

Factors Affecting Electrolysis

• The position of the ion in the electrochemical series affects its ease of discharge.
• Higher concentration ions have a greater chance of being discharged.
• The nature of the electrode can influence which ion is discharged.

Electrolysis of Molten Lead Bromide

• Lead bromide (PbBr₂) is a molten electrolyte.
• Molten lead bromide dissociates into Pb²⁺ and 2Br⁻ ions.
• Lead (Pb) is deposited at the cathode.
• Bromine (Br₂) is produced at the anode.

Electrolysis of Acidified Water

• Acidified water (H₂O with a small amount of H₂SO₄) is an electrolyte.
• Water dissociates into H⁺ and OH⁻ ions.
• H⁺ ions are discharged at the cathode, forming hydrogen gas (H₂).
• OH⁻ ions are discharged at the anode, forming oxygen gas (O₂).

Electrolysis of Aqueous Copper (II) Sulphate

• Aqueous copper (II) sulphate (CuSO₄) is an electrolyte.
• Copper (Cu²⁺) and sulphate (SO₄²⁻) ions are present.
• At the cathode, Cu²⁺ ions gain electrons to produce copper metal (Cu).
• At the anode, copper metal (Cu) loses electrons, producing Cu²⁺ ions, which remain in the solution.
• The color of the solution does not change with the copper electrodes.

Electroplating

• Electroplating is the process of depositing a thin layer of a metal onto another metal using electrolysis.
• The object to be plated acts as the cathode.
• The metal to be plated acts as the anode.
• An electrolyte containing ions of the plating metal is used.
• A direct current is used to carry out the process.

Electrorefining

• Electrorefining is the process of purifying a metal using electrolysis.
• An impure block of metal acts as the anode.
• A pure sheet of the same metal acts as the cathode.
• An electrolyte containing ions of the metal is used.
• Impurities from the impure metal settle at the bottom of the cell, forming anode mud.

Electrochemical Series

• The electrochemical series arranges metals in order of their reactivity.
• Easily oxidized metals (those that lose electrons readily) are at the top of the series, and those that are less easily oxidized are at the bottom.
• Metals at the top of the series are more reactive.