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AQA GCSE Chemistry Electrolysis in Experiment

Electrolysis in Experiment

This page covers the following topics:

1. Electrolysis of Aqueous Solutions
2. Production of gases
3. Electrolysis of Molton Ionic Salts
4. Electrolysis of Molton Ionic Salts

In electrolysis of aqueous solutions you must use unreactive materials (such as graphite) for electrodes to prevent unwanted reactions between the electrode and the solution. Aqueous salt solutions contain hydrogen, hydroxide, metal and non metal ions. In dilute halide salt solutions the oxygen ions outnumber the halide ions so oxygen forms at the anode.

Electrolysis of Aqueous Solutions

There can be many products of the electrolysis of aqueous solutions including hydrogen, oxygen or halide gases and solid metals. You can determine which gas is produced as oxygen gas will relight a glowing splint, hydrogen gas will produce a squeaky pop sound with a glowing splint and chlorine gas turns damp blue litmus paper red.

Production of gases

In the electrolysis of molten salts only the metal and non metal ions of the salt are present (no hydrogen or hydroxide from water). The salt must be melted by a heat source, e.g. bunsen burner. Electrolysis of lead bromide is commonly used to demonstrate molten salt electrolysis due to its relatively low melting point.

Electrolysis of Molton Ionic Salts

In molten electrolyte electrolysis, a metal is always formed at the cathode and non-metal is formed at the anode. Halide gases such as chlorine or bromine are commonly produced. Bromine gas is brown and pungent smelling.

Electrolysis of Molton Ionic Salts

1

The electrolysis of a molten ionic compound results in a silver metal formed at the cathode and brown, pungent smelling gas produced at the anode. Suggest a compound that could produce these observations.

The electrolysis of a molten ionic compound results in a silver metal formed at the cathode and brown, pungent smelling gas produced at the anode. Suggest a compound that could produce these observations.

2

In the electrolysis of aqueous sodium chloride what would you observe?

In the electrolysis of aqueous sodium chloride what would you observe?

3

What will be the reactions at each electrode for the electrolysis shown?

What will be the reactions at each electrode for the electrolysis shown?

4

How do you test for chlorine gas?

How do you test for chlorine gas?

5

What ions would you expect to have in molten copper sulphate?

What ions would you expect to have in molten copper sulphate?

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