Electrolysis

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Introduction

Electrolysis is the process by which ionic substances are broken down into simpler substances using electricity. During electrolysis, metals and gases may form at the electrodes.

What is electrolysis?

Ionic substances contain charged particles called ions. For example, lead bromide contains positively charged lead ions and negatively charged bromide ions.

Electrolysis is the process by which ionic substances are decomposed (broken down) into simpler substances when an electric current is passed through them.

For electrolysis to work, the ions must be free to move. Ions are free to move when an ionic substance is dissolved in water or when melted. For example, if electricity is passed through molten lead bromide, the lead bromide is broken down to form lead and bromine.

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What happens during electrolysis

Here is what happens during electrolysis:

  • Positively charged ions move to the negative electrode during electrolysis. They receive electrons and are reduced.
  • Negatively charged ions move to the positive electrode during electrolysis. They lose electrons and are oxidised.

The substance that is broken down is called the electrolyte.

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Electroplating

Electrolysis is used to electroplate objects. This is useful for coating a cheaper metal with a more expensive one, such as copper or silver.

How it works

  • The negative electrode should be the object that is to be electroplated
  • The positive electrode should be the metal that you want to coat the object with
  • The electrolyte should be a solution of the coating metal, such as its metal nitrate or sulfate
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