Advanced Topic 571 of 1102 Acids, Bases & Electrochemistry
Faraday's Second Law
Masses deposited by the same charge are proportional to equivalent weights.
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In-depth explanation of Faraday's Second Law
Faraday's second law extends the first by showing that when the same quantity of charge passes through different electrolytes, the masses deposited are proportional to their equivalent weights, which are the molar masses divided by the number of electrons transferred. One mole of electrons therefore deposits one equivalent of any element, regardless of which element it is. This is why the electron charge defines the chemical equivalent of an element. The law explains why silver and copper deposit different masses in the same circuit. It is a foundation for quantitative electrochemical analysis.
Going deeper: Faraday's Second Law
Key ideas: For the same charge passed through different electrolytes in series, masses deposited are proportional to equivalent masses (M/n). Silver and copper cells in series: m(Cu)/m(Ag) = (63.5/2)/(107.9/1). Equal charge liberates 1 mol of Ag, 0.5 mol of Cu, or 0.33 mol of Al.
Common mistakes and connections: Students forget the cells must be in series so the same current flows, and mix up equivalent mass with molar mass. In parallel, current divides. Use the law to find unknown atomic mass or oxidation state from deposition ratios. It follows from the same mole-of-electrons logic as the first law.
Visualization of Faraday's Second Law
Mass deposited by one mole of electrons equals the equivalent weight (molar mass divided by charge), the second law: 107.9 g of Ag but 31.8 g of Cu. The interactive lesson shows this as a live animation or chart.
Worked example and use case
The same charge deposits 107.9 g of silver from Ag+ but only 31.8 g of copper from Cu2+.
Frequently asked questions about Faraday's Second Law
What is Faraday's Second Law?
Masses deposited by the same charge are proportional to equivalent weights.
Is Faraday's Second Law a beginner, intermediate or advanced topic?
Faraday's Second Law is a advanced topic in Acids, Bases & Electrochemistry. It builds on beginner and intermediate topics, so review those first if needed.
What should I learn before Faraday's Second Law?
Study these earlier topics in Acids, Bases & Electrochemistry first: Concentration Cells, Faraday's Constant, Faraday's First Law.
What comes after Faraday's Second Law?
The next topics in Acids, Bases & Electrochemistry are Electrolysis of Molten Salts and Electrolysis of Aqueous Solutions.
Can I practise Faraday's Second Law with quizzes?
Yes. The interactive lesson includes a self-check question on Faraday's Second Law, and the Acids, Bases & Electrochemistry quiz draws on every topic in this area.
Where Faraday's Second Law fits in Acids, Bases & Electrochemistry
Faraday's Second Law is topic 61 of 105 in Acids, Bases & Electrochemistry.