7.1.5

Electrolysis - Examples

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Electrolysis Examples

You need to be able to describe the electrode products and the observations made during the electrolysis of:

Molten lead(II) bromide

Molten lead(II) bromide

  • When we use graphite electrodes to apply electricity across molten lead bromide, we form lead (metal) at the cathode and bromine (non-metal) at the anode.
    • Lead bromide → lead + bromine
  • We know lead is present if a shiny metal forms around the cathode.
  • Bromine is observed as a brown gas because of the high temperatures reached in the process.
Concentrated hydrochloric acid

Concentrated hydrochloric acid

  • Applying electricity across hydrochloric acid with graphite electrodes produces hydrogen gas at the cathode and chlorine gas (non-metal) at the anode.
  • We can detect hydrogen at the cathode using a lit splint. A squeaky pop is heard.
  • We can detect chlorine gas by its smell. It also bleaches litmus paper.
Concentrated aqueous sodium chloride

Concentrated aqueous sodium chloride

  • The electrolysis of aqueous solutions is a little more complex, as you have to consider the water.
  • In the case of aqueous sodium chloride, hydrogen is formed instead of sodium.
  • Applying electricity across aqueous sodium chloride produces hydrogen gas at the cathode and chlorine gas (non-metal) at the anode.
  • The electrodes are inert graphite or platinum.
  • The formation of hydrogen at the cathode can be detected using a lit splint. A squeaky pop is heard.
  • The chlorine gas can be detected by its smell. It also bleaches litmus paper.
Dilute sulfuric acid

Dilute sulfuric acid

  • When dilute sulfuric acid is electrolysed, hydrogen is produced from the acid and oxygen from the water.
  • Applying electricity to sulfuric acid with graphite electrodes produces hydrogen gas at the cathode and oxygen at the anode.
  • The formation of hydrogen at the cathode can be detected using a lit splint. A squeaky pop is heard.
  • The oxygen gas produced at the anode can also be detected using a glowing splint. The splint will relight in oxygen gas.
Jump to other topics
1

States of Matter

2

Elements, Compounds & Mixtures

3

Atomic Structure

4

The Periodic Table

5

Chemical Formulae, Equations & Calculations

6

Bonding

7

Electrolysis

8

Groups of the Periodic Table

9

The Atmosphere

10

Reactivity Series

11

Metal Extraction

12

Acids & Alkalis

13

Chemical Tests

14

Physical Chemistry

15

Organic Chemistry

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