Question 1

What is Faraday's first law of electrolysis?

Accepted Answer

Faraday's first law states that the mass of substance deposited or liberated at an electrode is directly proportional to the quantity of electric charge passed. Mathematically, m = (Q × M) / (n × F), where Q is charge in coulombs, M is molar mass, n is the number of electrons transferred per ion, and F is Faraday's constant (96,485 C/mol). Passing more current for longer produces more product.

Question 2

Why does water electrolysis require more than 1.23 V?

Accepted Answer

The thermodynamic decomposition voltage for water is 1.23 V, derived from the Gibbs free energy of the reaction. In practice, overpotentials at both electrodes (especially the oxygen evolution overpotential), ohmic losses in the electrolyte, and contact resistances add up to require 1.8–2.0 V or more. Catalysts like platinum or iridium oxide reduce overpotentials, improving efficiency.

Question 3

What determines whether a substance is reduced at the cathode?

Accepted Answer

The electrode reaction that occurs is determined by standard reduction potentials. Species with the most positive reduction potential are reduced preferentially. In a brine solution, although Na+ is present, water is reduced to H2 instead because H2O/H2 has a higher reduction potential than Na+/Na under typical conditions. Temperature, concentration, and electrode material all influence the actual reaction.

⚡ Electrolysis

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