What is the role of a salt bridge in a galvanic cell?

A salt bridge (usually KCl or KNO₃ in agar gel) serves two functions: (1) It completes the electrical circuit by allowing ions to migrate between the two half-cells; (2) It maintains electrical neutrality — as Zn²⁺ accumulates in the anode half-cell and Cu²⁺ is consumed in the cathode half-cell, ions from the salt bridge migrate to balance charges and prevent the cell from stopping.

What does a positive E°cell value indicate?

A positive E°cell value indicates: (1) The reaction is spontaneous in the forward direction; (2) ΔG° = −nFE°cell is negative (spontaneous); (3) K_eq > 1 (products favoured at equilibrium). A negative E°cell means the reaction is non-spontaneous as written, but spontaneous in reverse.

State Faraday's First Law of Electrolysis.

Faraday's First Law: The mass of substance deposited or liberated at an electrode during electrolysis is directly proportional to the quantity of charge passed. m = ZQ = ZIt, where Z = electrochemical equivalent (mass deposited per coulomb) = M/(nF). Practical: to deposit 1 mole of Cu (M=64, n=2): Q = 2 × 96500 = 193,000 C = 2 Faraday.

Electrochemical Cells and Nernst Equation

Electrochemistry • Class 12 Chemistry • NCERT • CBSE

Standard cell EMF: E°cell = E°cathode − E°anode. Nernst Equation: E_cell = E°cell − (RT/nF)ln Q = E°cell − (0.0592/n)log Q at 25°C. Faraday's First Law: m = ZQ = ZIt. Molar conductivity Λm = k × 1000/M.

Key Formulas

E°cell = E°cathode − E°anode
E_cell = E°cell − (0.0592/n)log Q
log K_eq = nE°cell/0.0592
ΔG° = −nFE°cell
m = (M/nF)×I×t (Faraday's law)

Frequently Asked Questions

What is the role of a salt bridge in a galvanic cell?: A salt bridge (usually KCl or KNO₃ in agar gel) serves two functions: (1) It completes the electrical circuit by allowing ions to migrate between the two half-cells; (2) It maintains electrical neutrality — as Zn²⁺ accumulates in the anode half-cell and Cu²⁺ is consumed in the cathode half-cell, ions from the salt bridge migrate to balance charges and prevent the cell from stopping.
What does a positive E°cell value indicate?: A positive E°cell value indicates: (1) The reaction is spontaneous in the forward direction; (2) ΔG° = −nFE°cell is negative (spontaneous); (3) K_eq > 1 (products favoured at equilibrium). A negative E°cell means the reaction is non-spontaneous as written, but spontaneous in reverse.
State Faraday's First Law of Electrolysis.: Faraday's First Law: The mass of substance deposited or liberated at an electrode during electrolysis is directly proportional to the quantity of charge passed. m = ZQ = ZIt, where Z = electrochemical equivalent (mass deposited per coulomb) = M/(nF). Practical: to deposit 1 mole of Cu (M=64, n=2): Q = 2 × 96500 = 193,000 C = 2 Faraday.

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