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The substance broken down by electrolysis is called the electrolyte.

Electrolysis 1

Electrolysis uses electricity to split ionic substances. This GCSE Chemistry quiz checks electrodes, ion movement, and what forms at each electrode in molten salts and solutions.

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Fascinating Fact:

Reduction happens at the cathode because ions gain electrons. Oxidation happens at the anode because ions lose electrons.

In GCSE Chemistry, electrolysis helps you understand how ionic compounds behave when they are molten or dissolved. You learn how ions move to electrodes, why metals or gases can form, and how electrolysis is used in industry to extract and purify substances.

Key Terms

Electrolysis: Using an electric current to break down an ionic compound into simpler substances.
Cathode: The negative electrode that attracts positive ions (cations) during electrolysis.
Anode: The positive electrode that attracts negative ions (anions) during electrolysis.

Frequently Asked Questions (Click to see answers)

What happens at the cathode in electrolysis?

At the cathode, positive ions gain electrons and are reduced. In molten salts this often forms a metal, and in aqueous solutions hydrogen can form if it is easier to produce than the metal.

Why must an ionic compound be molten or in solution for electrolysis?

Ions must be free to move so they can carry charge to the electrodes. In a solid ionic compound the ions are fixed in place, so it cannot conduct electricity and electrolysis cannot occur.

How do you predict the products of electrolysis of an aqueous solution?

In aqueous solutions, water can also be discharged. At the cathode, hydrogen forms unless the metal is less reactive than hydrogen, and at the anode either chlorine forms from chloride ions or oxygen forms from hydroxide ions.

Try These Related Quizzes

1 .

Pick the correct half equations to show what happens when PbBr₂ is electrolysed.

Cathode: Pb⁺ + e^- → Pb
Anode: 2Br^- → Br₂ + 2e^-

Anode: Pb²⁺ + 2e^- → Pb
Cathode: 2Br^- → Br₂ + 2e^-

Cathode: Pb²⁺ + 2e^- → Pb
Anode: Br^- → Br + 2e^-

Cathode: Pb²⁺ +2e^- → Pb
Anode: 2Br^- → Br₂ + 2e^-

This is only going to come up in the higher tier of the exam

2 .

Electrolysis means which of the following?

Splitting up substances using heat

Splitting up substances using electrons

Splitting up substances using electricity

Joining up substances using electricity

It is a chemical decomposition

3 .

When lead bromide is electrolysed...

Pb²⁺ is reduced at the cathode, Br^- is oxidised at the anode

Pb²⁺ is oxidised at the cathode, Br^- is reduced at the anode

Pb²⁺ is reduced at the anode, Br^- is oxidised at the cathode

Pb³⁺ is reduced at the cathode, Br^- is oxidised at the anode

Reduction is a gain of electrons and oxidation is a loss of electrons. Metals are produced from their ores by reduction of their ions

4 .

When a negatively charged ion reaches the positively charged electrode...

It can lose an electron to become a neutral atom

It can lose an electron to become a positive ion

It gains an electron to become a neutral atom

It gains an electron to become a negative ion

Many anions (e.g sulfate - SO₄^2-) are too stable to lose their electron and in those cases oxygen is released from the small quantity of hydroxide ions that are always present in water. Substances containing the stable anions are therefore only electrolytes when in solution

5 .

During electrolysis...

+ve ions move to cathode and -ve ions move to anode

+ve ions move to anode and -ve ions move to cathode

+ve ions and -ve ions move to cathode

+ve ions and -ve ions move to anode

Remember: opposite charges attract

6 .

Pick the correct half equations to show what happens when an aqueous solution of KCL is electrolysed.

Cathode: K⁺ + e^- → K
Anode: 2Cl^- → Cl₂ +2e^-

Cathode: 2H⁺ + 2e^- → H₂
Anode: 2Cl^- → Cl₂ + 2e^-

Cathode: H⁺ + e^- → H
Anode: 2Cl^- → Cl₂ +2e^-

Cathode: K⁺ + e^- → K
Anode: Cl^- → Cl + e^-

Hydrogen gas is produced because it is less reactive than potassium

7 .

Pick the correct combination for the names of the positive and negative electrodes.

+ve anode -ve negode

+ve cathode -ve anode

+ve posode -ve cathode

+ve anode -ve cathode

Electrodes get their names from the type of ion they attract

8 .

What do we call the substance broken down by electrolysis?

Solvent

Solute

Substrate

Electrolyte

This word is reasonably easy to remember being so close to electrolysis. An electrolyte must separate into positive and negative ions when it is molten or dissolved in water

9 .

Why does an electrolyte need to be either molten or in solution?

To ensure the atoms can move

To enable the ions to move

So that water ions can be involved in the reaction

So that the electrodes can be put in the electrolyte

If the electrolyte is solid, the ions are unable to move and so electricity cannot flow. You should have discarded the first option the second you read the word 'atoms' - atoms have no overall charge and therfore are unaffected by electrolysis

10 .

Pick the correct combination to show what is collected at each electrode when molten copper bromide is electrolysed.

Copper ions at the cathode, Bromine gas at the anode

Copper metal at the anode, Bromide ions at the cathode

Copper metal at the cathode, Bromine gas at the anode

Copper metal at the anode, Bromine gas at the cathode

Bromine has a red-brown colour and its molecules are diatomic (contain 2 atoms bonded covalently so its formula is Br₂)

You can find more about this topic by visiting BBC Bitesize - Electrolysis

Author: Kate Gardiner (Chemistry Educator & GCSE Quiz Writer)

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