Chemistry (9-1) - 0971 CIE

Electrolysis

Overview

Pass an electric current through a molten salt and something remarkable happens: the compound splits apart, with a metal appearing at one electrode and a non-metal at the other. This is electrolysis, the use of electricity to break down a compound that no simple chemical reaction could.

In this lesson you will learn what electrolysis is, the meaning of the key terms electrolyte, electrode, cathode and anode, and how a molten ionic compound is decomposed. Molten lead(II) bromide is the worked example.

Objectives

  1. Define electrolysis as the decomposition of an ionic compound, when molten or in aqueous solution, by the passage of an electric current.
  2. Identify in simple electrolytic cells: (a) the anode as the positive electrode (b) the cathode as the negative electrode (c) the electrolyte as the molten or aqueous substance that undergoes electrolysis.
  3. [Supplement] Describe the transfer of charge during electrolysis to include: (a) the movement of electrons in the external circuit (b) the loss or gain of electrons at the electrodes (c) the movement of ions in the electrolyte.

Lesson Note

Electrolysis is how reactive metals such as aluminium are extracted, how metals are purified and how objects are electroplated. It is one of the most important industrial processes, and it rests on the simple idea of using electricity to move ions and force a reaction.

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Lesson Evaluation

Congratulations on completing the lesson on Electrolysis. Now that youve explored the key concepts and ideas, its time to put your knowledge to the test. This section offers a variety of practice questions designed to reinforce your understanding and help you gauge your grasp of the material.

You will encounter a mix of question types, including multiple-choice questions, short answer questions, and essay questions. Each question is thoughtfully crafted to assess different aspects of your knowledge and critical thinking skills.

Use this evaluation section as an opportunity to reinforce your understanding of the topic and to identify any areas where you may need additional study. Don't be discouraged by any challenges you encounter; instead, view them as opportunities for growth and improvement.

  1. Electrolysis is the breakdown of an ionic compound by: A. Heating alone B. Passing an electric current through it C. Adding water D. Adding an acid Answer: B
  2. An electrolyte conducts electricity when it is: A. Solid B. Molten or dissolved C. Frozen D. Pure and dry Answer: B
  3. The cathode in an electrolysis cell is: A. Positive and attracts positive ions B. Negative and attracts positive ions C. Negative and attracts negative ions D. Positive and attracts negative ions Answer: B
  4. During the electrolysis of molten lead(II) bromide, the product at the cathode is: A. Bromine B. Lead C. Oxygen D. Hydrogen Answer: B
  5. Inert electrodes are often made of: A. Sodium B. Carbon or platinum C. Iron D. Lead Answer: B

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Full lesson notes with diagrams
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Available on the Green Bridge App

Download the Green Bridge CBT app on your phone or computer to access full lesson notes, practice questions, and more.

Full lesson notes with diagrams
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Study offline, anytime, anywhere
Available on Android, Windows, macOS, and Linux

Practice Mock Questions

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