Govt Exams
Rusting of iron is a corrosion process (galvanic corrosion) and not a direct application like electroplating, electrolysis, or electrorefining.
When E°cell is negative, ΔG° = -nFE°cell will be positive, indicating a non-spontaneous reaction under standard conditions.
In a galvanic cell, oxidation occurs at the anode (negative electrode), while reduction occurs at the cathode (positive electrode).
For a spontaneous cell reaction, E°cell > 0 (positive). When E°cell is negative, the reaction is non-spontaneous. E°cell = E°cathode - E°anode.
By international convention, the standard reduction potential of H⁺/H₂ couple is taken as 0.00 V at 25°C. This serves as the reference electrode for all other electrode potentials.
Faraday constant (F) = 96485 Coulombs per mole of electrons. This represents the charge carried by one mole of electrons.
In a galvanic cell, oxidation occurs at the anode. The anode is the negative electrode where electrons are released and the species loses electrons.
In electroplating, the object to be plated is made the cathode (negative terminal) where reduction occurs, causing metal deposition.
A dry cell or Leclanche cell is a primary cell that cannot be recharged. Lead-acid and Ni-Cd are secondary cells; Li-ion is rechargeable.
The Nernst equation: E = E° - (RT/nF)ln(Q) calculates the cell potential when concentrations are not at standard state (1 M).