Important Concepts in Electrochemistry

Electrochemistry

• Electrolytic cells vs. galvanic cells: Remember that electrolytic cells require an external power source to drive a non-spontaneous reaction. Galvanic cells undergo a spontaneous reaction, generating electricity.

• Anode and cathode: The anode is where oxidation occurs (loss of electrons), and the cathode is where reduction occurs (gain of electrons). Remember “OIL RIG” - Oxidation Is Loss, Reduction Is Gain.

• Oxidation and reduction: Redox reactions involve one species being oxidized and another reduced, with a transfer of electrons. In an oxidation-reduction reaction, remember to balance both the atoms and the charges.

• Balancing redox reactions: Balancing redox reactions requires balancing both charges and elements. You can do this by adding water molecules, hydrogen ions (H+), or hydroxide ions (OH-) as needed.

• Faraday’s law of electrolysis: Faraday’s law states that the amount of substance deposited or dissolved at an electrode during electrolysis is directly proportional to the amount of electricity that passes through the electrode. Remember that 1 mole of electrons carries a charge of 96,485 coulombs.

• Nernst equation: The Nernst equation relates the cell potential to the standard cell potential, temperature, and concentrations of reactants and products. For every tenfold difference in concentration, the cell potential changes by approximately 0.0592 volts at room temperature.

• Cell potential: The cell potential (Ecell) is the difference in electrical potential between the anode and the cathode. A positive Ecell indicates a spontaneous reaction, while a negative Ecell indicates a non-spontaneous reaction.

• Types of electrodes: Electrodes can be classified into different types based on their composition and function. Some common electrode types include inert electrodes (e.g., platinum), active electrodes (e.g., iron in a rusting process), and reference electrodes (e.g., the standard hydrogen electrode).

• Polarisation: Polarisation is the phenomenon in electrochemical cells where the cell potential deviates from its ideal value due to factors such as concentration gradients, electrode kinetics, and solution resistance. Remember that polarisation can lead to overpotentials, which are additional voltages required to drive the desired reaction.

Electrolysis

• Factors affecting the rate of electrolysis: The rate of electrolysis is influenced by several factors, including the concentration of the electrolyte solution, the surface area of the electrodes, the distance between the electrodes, the applied voltage, and the temperature.

• Applications of electrolysis: Electrolysis has numerous practical applications, including electroplating, refining of metals, production of chemicals (e.g., chlorine and sodium hydroxide), and electrorefining of metals.

Batteries and fuel cells

• Types of batteries: There are different types of batteries, such as primary (non-rechargeable) batteries, secondary (rechargeable) batteries, and flow batteries. Each type has its own characteristics and applications.

• Cell potential and emf: The cell potential of a battery is related to the energy released or stored during the electrochemical reaction. The emf (electromotive force) represents the maximum potential difference between the electrodes under standard conditions.

• Rechargeable batteries: Rechargeable batteries undergo reversible electrochemical reactions, allowing them to be recharged multiple times. Examples include lead-acid batteries, lithium-ion batteries, and nickel-metal hydride batteries.

• Fuel cells: Fuel cells generate electricity through electrochemical reactions involving a continuous supply of fuel (e.g., hydrogen) and an oxidant (e.g., oxygen). They are environmentally friendly and have potential applications in transportation, power generation, and portable devices.

Corrosion

• Types of corrosion: Corrosion is the deterioration of metal due to electrochemical reactions with the surroundings. Common types of corrosion include uniform corrosion, galvanic corrosion, crevice corrosion, and stress corrosion cracking.

• Factors affecting the rate of corrosion: Corrosion rate is influenced by various factors, such as the presence of moisture, electrolytes (e.g., salts), oxygen, temperature, pH, and the nature of the metal.

• Prevention of corrosion: Corrosion can be prevented or minimized through several techniques, including protective coatings, cathodic protection, anodic protection, corrosion-resistant alloys, and proper maintenance.

Electroplating

• Applications of electroplating: Electroplating involves depositing a thin layer of metal on a conductive surface through electrolysis. It has numerous applications, including enhancing corrosion resistance, improving appearance, imparting specific properties (e.g., electrical conductivity), and for decorative purposes.

Remember to review each concept regularly and practice applying the knowledge to solve problems or explain real-world scenarios related to electrochemistry.