Cambridge IGCSE · Chemistry 0620
IGCSE Chemistry: Electrochemistry — Practice Questions & Answers
How electricity decomposes ionic compounds: electrolysis rules, products, electroplating, copper purification, fuel cells and half equations.
712 practice questions available for this topic — here are 10 with full answers and explanations.
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Practice questions with answers
1
Multiple choice · Easy
What name is given to a liquid or solution that conducts electricity and is broken down by it?
- Electrolyte
- Electrode
- Conductor
- Insulator
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WhyAn electrolyte is an ionic compound, molten or in solution, that conducts electricity and is decomposed during electrolysis.
2
Multiple choice · Easy
In electrolysis, what is the name of the negative electrode?
- Cathode
- Anode
- Anion
- Cation
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WhyThe cathode is the negative electrode, to which positive ions (cations) are attracted.
3
Multiple choice · Easy
Which substance is commonly used to make the inert electrodes in many electrolysis experiments?
- Graphite (carbon)
- Sodium
- Sulfur
- Plastic
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WhyGraphite (carbon) and platinum are inert electrodes that conduct electricity but do not react during electrolysis.
4
Multiple choice · Easy
Why must an ionic compound be molten or dissolved before it can be electrolysed?
- The ions become free to move
- The compound turns into a metal
- Electrons are destroyed
- The compound becomes covalent
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WhyIn the solid state the ions are fixed in the lattice; melting or dissolving lets the ions move and carry charge.
5
Multiple choice · Easy
During the electrolysis of molten lead(II) bromide, which product forms at the cathode?
- Lead
- Bromine
- Hydrogen
- Oxygen
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WhyPositive lead ions (Pb2+) are attracted to the cathode where they gain electrons and are deposited as lead metal.
6
Fill in the blank · Easy
At the anode, negatively charged ions called lose electrons (oxidation).
Answer:
anions
WhyAnions are negative ions; they are attracted to the positive anode where they are oxidised by losing electrons.
7
Multiple choice · Medium
In the electrolysis of concentrated aqueous sodium chloride, which gas is produced at the anode?
- Chlorine
- Hydrogen
- Oxygen
- Sodium
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WhyWith concentrated chloride solution, chlorine is preferentially discharged at the anode instead of oxygen.
8
Multiple choice · Medium
During the electrolysis of dilute sulfuric acid with inert electrodes, what is produced at the cathode?
- Hydrogen gas
- Oxygen gas
- Sulfur
- Sulfur dioxide
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WhyHydrogen ions from the acid are discharged at the cathode, releasing hydrogen gas.
9
Multiple choice · Medium
In the electrolysis of aqueous copper(II) sulfate with inert (carbon) electrodes, what forms at the cathode?
- Copper
- Hydrogen
- Oxygen
- Sulfur
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WhyCopper is less reactive than hydrogen, so Cu2+ ions are discharged in preference and copper is deposited at the cathode.
10
Multiple choice · Medium
Which process uses electrolysis to coat an object with a thin layer of metal?
- Electroplating
- Galvanising by dipping
- Cracking
- Distillation
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WhyElectroplating uses electrolysis to deposit a thin metal layer onto an object for appearance or corrosion protection.
Key terms in Electrochemistry
Electrochemistry: The branch of chemistry concerned with the relationship between electricity and chemical reactions.
Electrolysis: The breakdown of an ionic compound, when molten or in aqueous solution, using an electric current.
Electrolyte: A molten or aqueous ionic substance that conducts electricity and is decomposed during electrolysis.
Non-electrolyte: A substance that does not conduct electricity because it contains no free-moving ions.
Strong electrolyte: An electrolyte that is fully ionised in solution and therefore conducts electricity well.
Weak electrolyte: An electrolyte that is only partly ionised in solution and therefore conducts electricity poorly.
Electrode: A solid conductor through which electric current enters or leaves an electrolyte during electrolysis.
Anode: The positive electrode in electrolysis, towards which negative ions move and at which oxidation occurs.
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