Revision: Redox Reactions and Electrochemistry JEE Main Redox Reactions and Electrochemistry

The electrode at which the reduction occur is called cathode.

Fuel cells are the galvanic cells in which the energy of combustion of fuels like hydrogen, methanol, etc., is directly converted into electrical energy.

The electrode at which the oxidation occur is called anode.

Cell constant is the ratio of the distance between the electrodes divided by the area of cross-section of the electrode. It is denoted by b.
Thus, Cell constant = b =`l/a`. It is expressed in unit m⁻¹.

It is the inverse of resistance R and may be simply defined as the speed through which current flows in a conductor.

c = `1/R = A/(pl)`

k = `A/l`

Here k is the specific conductance. The SI unit of conductance is Siemens, which is denoted by the symbol ‘S’ and is equal to ohm⁻¹ or Ω⁻¹.

The limiting molar conductivity of an electrolyte is defined as its molar conductivity when the concentration of the electrolyte in the solution approaches zero.

When the concentration of an electrolytic solution placed between electrodes of a conductivity cell placed at a unit distance having an area of cross-section sufficient to accommodate enough volume of solution containing one mole of electrolyte approaches zero, then the conductance of the solution is known as limiting molar conductivity.

Molar conductivity is the conductance of a volume of solution containing 1 mole of dissolved electrolyte when placed between two parallel electrodes 1 cm apart and large enough to contain between them all the solution.

The conductivity, which is shown by all the ions when 1 mol of electrolyte is dissolved in the solution, is called molar conductivity; it is expressed by ∧_m (lambda). If 1 mol of electrolyte is present in V_m cm³ of electrolyte solution, then ∧_m = κ × V

= `(kappa xx 1000)/"Molarity" = (kappa xx 1000)/M`

Its unit is ohm⁻¹ cm² mol⁻¹ or S cm² mol⁻¹.

It is the process of decomposition of an electrolyte in the molten or aqueous state by discharge of ions at the electrodes on the passage of an electric current.

Electrolysis :
It is the process of decomposition of the electrolyte in the molten or aqueous state by discharge of ions at the elctrodes on passage of an electric current.

It is the process of decomposition of a chemical compound in aqueous solutions or in a molten state accompanied by a chemical change using direct electric current. 

Electroplating is a process in which a thin film of a metal like gold, silver, nickel, chromium, etc. gets deposited on another metallic article with the help of electricity.

Corrosion is the gradual damage of metals caused by their reaction with components of the atmosphere, such as oxygen and moisture.

Nernst equation can be given as,

`E = E^circ - (2.303 RT)/(nF) log_10  [["Products"]]/[["Reactants"]]`

where,

E° = Standard potential of electrode or cell,

n = Number of moles of electrons used in reaction,

F = Faraday = 96500 C/mol e⁻,

[Products] = Concentration of products,

[Reactants] = Concentration of reactants,

T = Temperature in K and

R = Gas constant = 8.314 J K⁻¹ mol⁻¹

Kohlrausch law states that at infinite dilution of the solution, each ion of electrolyte migrates independently of its co-ions and contribute independently to the total molar conductivity irrespective of the nature of other ion.

Kohlrausch’s law states that the molar conductivity of an electrolyte at infinite dilution is the same as the sum of the anions' and cations' limited molar conductivities.

`∧_m^° = v_+  λ_+^° + v_-  λ_-^°`

Here `λ_+^°` and `λ_-^°` are limiting molar conductivities of cations and anions.