Faraday’s Law of Electrolysis (Chemistry)

Lesson notes

Overview

The mass deposited is proportional to the charge passed. This topic is rated intermediate and is number 90 of 110 in Chemistry. Builds on the basics with relationships, methods and trade-offs.

What you are seeing

The panel above shows a graph of the function. Each slider changes one parameter, so you can see exactly how the curve bends, shifts or stretches. The animation is drawn live from the model, so everything you see responds to the sliders. Press Space to pause, use Restart to replay from the start, and change the speed to slow down quick events.

In depth

Faraday’s law says that the mass of a substance deposited or released at an electrode is proportional to the charge passed: m = (Q/F)(M/z), where F = 96,485 C/mol is the Faraday constant, M the molar mass and z the number of electrons per ion. Passing a current of 2 A for an hour through a copper sulfate solution deposits about 2.4 g of copper. It underlies electroplating and the industrial production of aluminium and chlorine.

Reading the relationship

The expression "m = (Q/F)(M/z)" is a compact summary of the idea. It uses the symbols m, Q, F, M, z; name what each one stands for before you start. Notice that it contains a ratio, so increasing the denominator makes the result smaller. Then use the sliders to see how changing one quantity changes the others.

A guided exploration

1. Set every slider to its middle value and note the shape of the curve. 2. Move one slider at a time and describe whether the curve shifts, stretches or turns. 3. Find the value where the behaviour changes sharply, then connect it to the formula.

Try this

Predict the outcome first, then test extreme slider values to find where the pattern changes or breaks.

Common pitfalls

Keep the particle picture in mind. Mistakes often come from treating a rate, an amount and an equilibrium position as the same thing, or from ignoring units and conditions.

How it connects

It builds on “Standard Cell Potentials”, the topic before it in Chemistry. Once you are comfortable, continue with “Entropy and Spontaneity”.

Why it matters

Chemistry links the tiny scale of atoms to the materials, medicines and energy we use every day.

Where you might use it

Revising “Faraday’s Law of Electrolysis” before a class, exam or certification
Predicting how fast a reaction runs in a lab or an industrial plant
Choosing materials, medicines and fuels based on how their atoms bond and react
Reading the labels and data sheets of cleaning products, batteries and food

Frequently asked questions

What is Faraday’s Law of Electrolysis?

The mass deposited is proportional to the charge passed. It is an intermediate topic in Chemistry.

How do I use the Faraday’s Law of Electrolysis simulation?

The panel at the top shows a graph of the function. Each slider changes one parameter, so you can see exactly how the curve bends, shifts or stretches. Move the sliders one at a time, then press Space to pause the animation and look closer.

What does the formula mean?

The expression m = (Q/F)(M/z) packs the idea into symbols. Name each symbol first, then change one quantity with the sliders and see which others respond.

Who is this topic for?

Builds on the basics with relationships, methods and trade-offs. If the quiz feels hard, reread the lesson notes and try the previous topic first.

What should I learn before this?

Start with “Standard Cell Potentials”, the previous topic in Chemistry. Each topic in a subject builds on the ones before it.

How do I track my progress?

Press “Mark as learned” on this page. Progress is stored only in this browser and is never sent anywhere. The Browse page can show topics you have learned or still need to learn.