Chapter 3 :- Electrochemistry
The field of science known as electrochemistry studies how chemical and electrical energy interact and how one form might change into another. Two metallic electrodes submerged in electrolytic solutions make up an electrochemical cell.
The cells come in two varieties:-
- Electrolytic cells
- Galvanic cells
Two half cells make up a galvanic cell. An electrolytic solution and a metallic electrode are both present in each half cell. The electrode where oxidation occurs is referred to as an anode, while the electrode where reduction occurs is referred to as a cathode.
A salt bridge or a permeable pot is used to keep the half-cells apart from one another.
A potential difference between two electrodes is shown by the flow of current between them.
The electromotive force is the difference in potential that causes current to flow from the electrode with a higher negative potential (emf).
Calculation of Electrical energy :-
Electrical energy is calculated as Emf (volts) x the amount of power (coulombs)
A random value of zero is given to SHE’s potential. E° = 0 V. It serves as a reference electrode for measuring the potentials of standard electrodes.
An electrochemical series is created when the components are placed in the order of their standard electrode potentials.
A cell’s average emf,
E0cell is equal to E0cathode, E0node, E0Riglit, and E0Left 9. “G°” = “-nFE0cell”
E0cell’s positivity would cause G° to be negative and the reaction to be spontaneous. The reaction would not occur naturally if E0cell is negative since G° would be positive.
A species with a higher standard reduction potential is more likely to take electrons and go through reduction, or the opposite is true.
The concentration of an ion affects how potential of an electrode in contact with its ions in solution changes. As a result, in a redox process,
For a cell that uses electrochemistry and whose total reaction is
The standard emf of the cell can be related to the equilibrium constant, A Cell.
Resistance measures how much a current flow is obstructed.
where R is the resistivity or specific resistance. The ohm is the unit of R. The resistance of a conductor with a length of 1 cm and a cross-sectional area of 1 cm2 is what is referred to as resistance.
Ohm-cm is the unit of resistivity.
The unit of conductance is the ohm-1, mho, or Siemens, and conductance is the reciprocal of resistance (S).
Specific resistance and specific conductance are inversely proportional.
READ MORE:– Chemistry Class 12 Chapter 2 – Solutions
The conductance of a solution in a cell with electrodes that are spaced a unit apart and each have an area equal to 1 cm2 is referred to as specific conductance. The ohm-1 cm-1 or S cm-1 unit of specific conductance is 18. The conductance of a volume of solution containing one mole of the solute and placed between two parallel electrodes spaced one centimetre apart and with enough surface area to retain the entire solution is known as molar conductance (m).
- Molar conductance is measured in units of S cm2 mol-1 or -1 cm2 mol-1.
- where C is the solution’s concentration in moles per litre (or Molarity).
- As the temperature rises, the electrical conductivity through metals decreases.
- As temperature rises, electrolytic conductance increases.
Dilution’s impact on :
(a) Equivalent conductance:
Equivalent conductance values grow with dilution and reach their highest levels at infinite dilution.
(b) Specific conductance:
As the amount of current-carrying particles, or ions, present per cm3 of solution drops with dilution, the value of specific conductance falls.
(c) Molar conductance:
As dilution proceeds, the value of molar conductance rises until it reaches its maximum value.
Molar conductance changes with concentration:
- Powerful electrolytes
- Weak electrolytes
where m is the mass of the material released or deposited.
Mass of deposited or released material A amperes of substance B’s deposited or released mass Z is a constant known as the electrochemical equivalent, and t is the time in seconds.
The weight of various substances deposited or released at the appropriate electrodes is proportional to their chemical equivalent weights when the same amount of electricity is transmitted through solutions of various electrolytes.
One mole of electrons carries about 96500 coulombs of charge. This amount of electricity is referred to as the Faraday constant (F).
A battery is made up of two or more series-connected galvanic cells. Batteries come in two varieties:
- Primary batteries
- Secondary batteries
(1) Primary batteries: When the reactants have been transformed into products in primary batteries, no more power can be generated. The battery goes dead because the cell reaction cannot be stopped.
(2) Secondary batteries: When energy is applied to secondary batteries (or cells), the cell response can be reversed (charging). It implies that the battery can be recharged and utilised repeatedly after a significant number of charging and discharging cycles.
These batteries are the most typical type of secondary battery.
Fuel cells are electrical devices that are activated to transform fuel combustion energy (hydrogen, carbon monoxide, methane, etc.) directly into electrical energy.
Metal corrosion is an electrochemical process. It happens when there is oxygen and water present