What is Faraday's constant?

Analyze the question: You are asked for the value of Faraday's constant. Each option is a different physical constant, so you only need to match each one to its name.

Explain the concept: Faraday's constant (F) is the magnitude of electric charge carried by one mole of electrons. It links the amount of substance deposited or liberated in electrolysis to the charge passed.

F = N_A × e = (6.022 × 10²³ mol⁻¹) × (1.602 × 10⁻¹⁹ C) ≈ 96,485 C/mol

In Nigerian exams you will often see it rounded to 96,500 C/mol.

Check each option:

• A. 6.022 × 10²³ mol⁻¹: This is Avogadro's constant, the number of particles in one mole.
• B. 3.00 × 10⁸ m/s: This is the speed of light in a vacuum.
• C. 9.81 m/s²: This is the acceleration due to gravity (g).
• D. 96,485 C/mol: This is Faraday's constant, the charge on one mole of electrons.

Why it matters (quick application): Faraday's first law of electrolysis says mass deposited = (Q × M) / (n × F), where Q = I × t. For example, to deposit 1 mole of Cu from Cu²⁺ (n = 2), you need 2 × 96,500 = 193,000 C.

Exam tip: Look at the unit. C/mol means charge per mole, which only Faraday's constant has. Also remember the link F = N_A × e, which helps you tell Avogadro's number and Faraday's constant apart.