Electrolysis Process: Electrolytic Cells

• Electrolysis is the process of using electricity to break down a chemical compound.
• Electrolysis involves passing an electric current through an electrolyte, causing it to decompose.
• Electrolytes are substances that conduct electricity when dissolved in water or in a molten state, due to the presence of mobile ions.
• Non-electrolytes do not conduct electricity because they do not form ions in solution.

Electrolytic Cell

• An electrolytic cell is the setup used to carry out electrolysis.
• It consists of two electrodes (cathode and anode) immersed in an electrolyte and connected to a DC power source.
• The cathode is the negative electrode where reduction occurs (gain of electrons).
• The anode is the positive electrode where oxidation occurs (loss of electrons).

Process of Electrolysis

• When an electric current is applied, ions in the electrolyte move towards the electrodes with opposite charges.
• Cations (positive ions) move towards the cathode and gain electrons (reduction).
• Anions (negative ions) move towards the anode and lose electrons (oxidation).
• The products of electrolysis are formed at the electrodes.

Factors Affecting Electrolysis

• Nature of the Electrolyte: The ions present in the electrolyte determine the products formed during electrolysis.
• Concentration of the Electrolyte: Higher concentration of ions may affect the rate of electrolysis and the products formed.
• Nature of Electrodes: Inert electrodes (e.g., platinum, graphite) do not participate in the reaction, while active electrodes (e.g., copper, silver) can react.
• Voltage Applied: A minimum voltage (decomposition potential) is required for electrolysis to occur.
• Temperature: Higher temperatures can increase the rate of electrolysis.

Electrolysis of Water

• Electrolysis of water involves the decomposition of water into hydrogen and oxygen gas using electricity.
• An electrolyte (e.g., dilute sulfuric acid or sodium hydroxide) is added to increase conductivity.
• At the cathode, hydrogen ions (H+) gain electrons to form hydrogen gas (H2).
• At the anode, hydroxide ions (OH-) lose electrons to form oxygen gas (O2) and water.
• The volume of hydrogen gas produced is twice the volume of oxygen gas.

Electrolysis of Aqueous Sodium Chloride (Brine)

• Electrolysis of brine (concentrated aqueous NaCl solution) produces hydrogen gas, chlorine gas, and sodium hydroxide.
• At the cathode, hydrogen ions are preferentially reduced to form hydrogen gas because they have a lower discharge potential than sodium ions.
• At the anode, chloride ions are oxidized to form chlorine gas.
• The remaining solution contains sodium ions and hydroxide ions, forming sodium hydroxide (NaOH).

Applications of Electrolysis

• Production of Metals: Used in the extraction and purification of metals like aluminum, copper, and gold.
• Production of Gases: Production of hydrogen, chlorine, and oxygen gas.
• Electroplating: Coating a metal object with a thin layer of another metal for protection or decoration.
• Electrolytic Refining: Purification of metals by electrolysis.
• Manufacturing of Chemicals: Production of various chemicals like sodium hydroxide and potassium hydroxide.