AQA · GCSE Chemistry 8462
AQA GCSE Chemistry: Chemical changes — Practice Questions & Answers
Reactivity series, metal extraction by reduction, acids and salts, neutralisation, the pH scale and electrolysis for AQA GCSE Chemistry.
1876 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
Which of the following metals is the most reactive according to the reactivity series?
- Potassium
- Iron
- Copper
- Sodium
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WhyPotassium sits near the top of the reactivity series, well above sodium, iron and copper, so it is the most reactive of these metals.
2
Multiple choice · Easy
What colour does universal indicator turn in a strongly acidic solution?
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WhyUniversal indicator turns red in strongly acidic conditions (low pH); it is green at neutral and purple in strong alkali.
3
Multiple choice · Easy
Which gas is produced when a reactive metal such as magnesium reacts with a dilute acid?
- Hydrogen
- Oxygen
- Carbon dioxide
- Chlorine
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WhyReactive metals react with dilute acids to form a salt and hydrogen gas, which can be tested with a lit splint that gives a squeaky pop.
4
Multiple choice · Easy
What is the pH value of a neutral solution such as pure water?
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WhyA neutral solution has a pH of 7. Values below 7 are acidic and values above 7 are alkaline.
5
Multiple choice · Easy
When an acid reacts with a base in a neutralisation reaction, which two products are always formed?
- A salt and water
- A salt and hydrogen
- Carbon dioxide and water
- A metal and oxygen
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WhyThe general neutralisation reaction is acid + base -> salt + water, so a salt and water are always produced.
6
Fill in the blank · Easy
During electrolysis, positively charged ions move towards the negative electrode, which is called the .
Answer:
cathode
WhyThe negative electrode is the cathode; positive ions (cations) are attracted to it during electrolysis.
7
Multiple choice · Medium
Which salt is formed when hydrochloric acid is neutralised by sodium hydroxide?
- Sodium chloride
- Sodium sulfate
- Sodium nitrate
- Sodium carbonate
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WhyHydrochloric acid produces chloride salts, so reaction with sodium hydroxide gives sodium chloride and water.
8
Multiple choice · Medium
A piece of iron is placed in copper sulfate solution and a copper coating forms. What does this displacement reaction show?
- Iron is more reactive than copper
- Copper is more reactive than iron
- Iron and copper are equally reactive
- No reaction has taken place
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WhyIron is more reactive than copper, so it displaces copper from the copper sulfate solution, depositing copper metal.
9
Multiple choice · Medium
Which gas is produced when a dilute acid reacts with a metal carbonate?
- Carbon dioxide
- Hydrogen
- Oxygen
- Ammonia
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WhyAcids react with carbonates to give a salt, water and carbon dioxide; the carbon dioxide turns limewater cloudy.
10
Multiple choice · Medium
Why is carbon used to extract iron from iron oxide in a blast furnace?
- Carbon is more reactive than iron, so it reduces the iron oxide
- Carbon is less reactive than iron
- Iron cannot be heated above its melting point
- Carbon is a metal
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WhyCarbon is more reactive than iron, so it can reduce iron oxide by removing the oxygen, leaving iron metal.
Key terms in Chemical changes
Reactivity series: A list of metals arranged in order of how readily they react, from most reactive at the top to least reactive at the bottom.
Metal: An element that typically loses electrons to form positive ions and conducts electricity and heat.
Non-metal: An element that typically gains or shares electrons and is usually a poor conductor of electricity.
Displacement reaction: A reaction in which a more reactive metal takes the place of a less reactive metal in a compound.
More reactive metal: A metal higher in the reactivity series that can displace a less reactive metal from its compounds.
Less reactive metal: A metal lower in the reactivity series that is displaced by metals above it.
Potassium: A very reactive Group 1 metal placed near the top of the reactivity series.
Sodium: A highly reactive Group 1 metal that reacts vigorously with water.
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