Electrochemistry

• Electrochemistry is the study of the production of electricity from energy released during spontaneous chemical reactions and the use of electrical energy to bring about non-spontaneous chemical transformations
• A large number of metals, sodium hydroxide, chlorine, fluorine, and many other chemicals are produced by electrochemical methods
• Batteries and fuel cells convert chemical energy into electrical energy and are used on a large scale in various instruments and devices
• Reactions carried out electrochemically can be energy efficient and less polluting, making the study of electrochemistry important for creating new eco-friendly technologies
• Transmission of sensory signals through cells to the brain and vice versa, as well as communication between cells, have an electrochemical origin
• In electrochemistry, an electrochemical cell can be described, and the differences between galvanic and electrolytic cells can be differentiated
• The Nernst equation can be applied to calculate the emf of a galvanic cell and define the standard potential of the cell
• The relation between the standard potential of the cell, Gibbs energy of the cell reaction, and its equilibrium constant can be derived
• Resistivity (r), conductivity (k), and molar conductivity (✆m) of ionic solutions can be defined
• Differentiation between ionic (electrolytic) and electronic conductivity can be explained
• The method for measuring the conductivity of electrolytic solutions and calculating their molar conductivity can be described
• The variation of conductivity and molar conductivity of solutions with changes in their concentration can be justified, and the term molar conductivity at zero concentration or infinite dilution (✆m) can be defined
• Kohlrausch law can be enunciated, and its applications can be learned
• Quantitative aspects of electrolysis can be understood
• The construction of some primary and secondary batteries and fuel cells can be described
• Corrosion as an electrochemical process can be explained
• The potential difference between the two electrodes of a galvanic cell is called the cell potential and is measured in volts
• Cell potential is the difference between the electrode potentials (reduction potentials) of the cathode and anode
• Cell electromotive force (emf) is the cell potential when no current is drawn through the cell
• In representing a galvanic cell, the anode is kept on the left and the cathode on the right
• A galvanic cell is generally represented by putting a vertical line between metal and electrolyte solution and a double vertical line between the two electrolytes connected by a salt bridge
• The emf of the cell is positive and is given by the potential of the half-cell on the right hand side minus the potential of the half-cell on the left hand side
• The potential of individual half-cells cannot be measured; only the difference between the two half-cell potentials that gives the emf of the cell can be measured
• The standard hydrogen electrode is assigned a zero potential at all temperatures
• The standard hydrogen electrode consists of a platinum electrode coated with platinum black, dipped in an acidic solution with pure hydrogen gas bubbled through it
• At 298 K, the emf of the cell constructed with the standard hydrogen electrode as the anode and the other half-cell as the cathode gives the reduction potential of the other half-cell
• If the standard electrode potential of an electrode is greater than zero, its reduced form is more stable compared to hydrogen gas; if it is negative, hydrogen gas is more stable than the reduced form of the species
• Electrochemical cells are extensively used for determining the pH of solutions, solubility product, equilibrium constant, and other thermodynamic properties
• The Nernst equation relates the cell potential to the concentrations of reactants and products in a general electrochemical reaction
• The Nernst equation at equilibrium provides a relationship between the standard potential of the cell and the equilibrium constant of the reaction
• The standard Gibbs energy for a reaction in the Daniell cell can be calculated using the standard electrode potential
• The resistance in electrical circuits is measured in ohms and is proportional to length and inversely proportional to the area of cross-section
• Standard Electrode Potentials at 298 K:

  • E o/V indicates the increasing strength of oxidising agents and reducing agents
  • A negative E o means the redox couple is a stronger reducing agent than the H+/H2 couple
  • A positive E o means the redox couple is a weaker reducing agent than the H+/H2 couple
• Equilibrium in the Daniell cell is reached when the concentrations of Zn2+ and Cu2+ ions stabilize, leading to a zero reading on the voltmeter
• The reversible work done by a galvanic cell is equal to the decrease in Gibbs energy, related to the cell potential and the charge passed
• The cell potential, E(cell), is determined by the concentrations of Cu2+ and Zn2+ ions, increasing with Cu2+ concentration and decreasing with Zn2+ concentration
• The resistivity, represented by the symbol ρ, is the constant of proportionality in the resistance equation and is measured in ohm meters
• In the Daniell cell, the electrode potential for Cu2+ and Zn2+ ions is calculated for the cathode and anode using specific equations
• Resistivity, also known as specific resistance, is the resistance of a substance when it is one meter long and has an area of cross-section of one square meter
• The SI unit for resistivity is ohm meter (Ω m), with the submultiple ohm centimeter (Ω cm) also being used