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Year 11 - Science

Half equations: electrolysis

Electrolysis

Unit Summary

This unit focuses on electrolysis, electrode reactions, and predicting products, including competing reactions in solutions. It explains metal extraction through electrolysis and writing ionic equations. It also covers tests for gases like oxygen, hydrogen, carbon dioxide, and chlorine.

Lesson Summary

You will learn to write half–equations and balanced ionic equations.

Key Notes

  • A half–equation describes what happens to one reactant in a reaction, such as the process at an individual electrode.
  • Half–equations show balanced charges as well as balanced atoms.
  • A balanced ionic equation shows all reacting ions involved in a reaction.
  • Ions not involved in a reaction do not appear in a balanced ionic equation.

Vocabulary To Learn

  • reduction: a type of reaction in which a substance gains electrons or loses oxygen
  • oxidation: a type of reaction in which a substance loses electrons or gains oxygen
  • half–equation: a chemical equation used to show the electrons lost in oxidation or the electrons gained in reduction
  • ionic equation: a balanced equation showing all the ions involved in a reaction
  • spectator ions: the ions not involved in a chemical reaction

Common Mistakes To Avoid

  • Getting the electrons confused; how many and which side of the half equations to write them on.

3 Quick Questions (With Answers)

1. Explain the scientific idea in this lesson using two key points.

A half–equation describes what happens to one reactant in a reaction, such as the process at an individual electrode. Half–equations show balanced charges as well as balanced atoms.

2. Define this scientific word and use it in context. 'reduction'

a type of reaction in which a substance gains electrons or loses oxygen. Include the word in a full scientific explanation, not as a single label.

3. Correct this common scientific misunderstanding.

Mistake: Getting the electrons confused; how many and which side of the half equations to write them on. Correction: When writing a half equation, electrons should be added and not taken away and so should go on the side of the equation where they are added. All charges must cancel each other out and the atoms on each side of the equation balance.

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