Chemical changes questions

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Chemical changes question collection

Review Chemical changes questions for Chemistry, with correct answers shown and coverage across acids, alkalis and neutralisation; reactivity series and displacement; electrolysis.

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Question 1

What is a chemical change?
  1. A process where new substances are formed
  2. A change of state only
  3. A process that can always be reversed by cooling
  4. Any mixing of two liquids

Question 2

Which observation is good evidence that a chemical reaction has happened?
  1. A gas is produced
  2. Ice melts in warm air
  3. Water boils when heated
  4. Sugar dissolves in water

Question 3

Which equation is balanced for magnesium burning in oxygen?
  1. \(2\mathrm{Mg} + \mathrm{O}_{2} \to 2\mathrm{MgO}\)
  2. \(\mathrm{Mg} + \mathrm{O}_{2} \to \mathrm{MgO}\)
  3. \(2\mathrm{Mg} + 2\mathrm{O}_{2} \to 2\mathrm{MgO}\)
  4. \(\mathrm{Mg} + \mathrm{O} \to \mathrm{MgO}_{2}\)

Question 4

What does an acid usually produce when it reacts with a metal?
  1. A salt and hydrogen
  2. A salt and oxygen
  3. A base and carbon dioxide
  4. Only water

Question 5

What are the products when an acid reacts with an alkali?
  1. A salt and water
  2. A salt and hydrogen
  3. A metal oxide and water
  4. A salt only

Question 6

What pH value is neutral?
  1. 7
  2. 0
  3. 1
  4. 14

Question 7

What color does blue litmus turn in an acid?
  1. Red
  2. Green
  3. Purple
  4. It stays blue

Question 8

What color does red litmus turn in an alkali?
  1. Blue
  2. Yellow
  3. Orange
  4. It stays red

Question 9

In KS3 chemistry, oxidation is commonly described as?
  1. Gain of oxygen
  2. Loss of oxygen
  3. Gain of electrons
  4. Loss of protons

Question 10

Reduction is commonly described as?
  1. Loss of oxygen
  2. Gain of oxygen
  3. Gain of neutrons
  4. Increase in pH only

Question 11

What is a displacement reaction?
  1. A more reactive element replaces a less reactive element from a compound
  2. Two elements share electrons equally
  3. A substance changes state from liquid to gas
  4. An acid always turns into an alkali

Question 12

Magnesium reacts with copper sulfate solution. What happens?
  1. Magnesium displaces copper
  2. Copper displaces magnesium
  3. No reaction because both are metals
  4. Magnesium turns into oxygen gas

Question 13

Which metal is more likely to react vigorously with dilute hydrochloric acid?
  1. Magnesium
  2. Copper
  3. Silver
  4. Gold

Question 14

Heating calcium carbonate causes thermal decomposition to form?
  1. Calcium oxide and carbon dioxide
  2. Calcium and oxygen
  3. Calcium hydroxide only
  4. Carbon and oxygen

Question 15

Which word equation shows neutralisation?
  1. \(\text{Hydrochloric acid} + \text{sodium hydroxide} \to \text{sodium chloride} + \text{water}\)
  2. \(\text{Hydrochloric acid} + \text{zinc} \to \text{zinc chloride} + \text{hydrogen}\)
  3. \(\text{Methane} + \text{oxygen} \to \text{carbon dioxide} + \text{water}\)
  4. \(\text{Copper carbonate} \to \text{copper oxide} + \text{carbon dioxide}\)

Question 16

What is the test for hydrogen gas?
  1. A lit splint gives a squeaky pop
  2. Glowing splint relights
  3. Limewater turns milky
  4. Damp blue litmus turns red

Question 17

What is the test for carbon dioxide gas?
  1. Limewater turns milky
  2. A lit splint gives a squeaky pop
  3. Glowing splint relights
  4. Blue litmus turns red then bleaches

Question 18

What does a catalyst do in a chemical reaction?
  1. Increases the rate without being used up
  2. Decreases the amount of products made
  3. Changes reactants into a different element
  4. Is always a gas

Question 19

Are combustion reactions usually exothermic or endothermic?
  1. Exothermic
  2. Endothermic
  3. Neutral
  4. Always reversible

Question 20

Which symbol equation represents neutralisation?
  1. \(\mathrm{HCl} + \mathrm{NaOH} \to \mathrm{NaCl} + \mathrm{H}_{2}\mathrm{O}\)
  2. \(\mathrm{HCl} + \mathrm{Na} \to \mathrm{NaCl} + \mathrm{H}_{2}\)
  3. \(2\mathrm{H}_{2} + \mathrm{O}_{2} \to 2\mathrm{H}_{2}\mathrm{O}\)
  4. \(\mathrm{CaCO}_{3} \to \mathrm{CaO} + \mathrm{CO}_{2}\)

Question 21

Which metal is least reactive in this list?
  1. Gold
  2. Magnesium
  3. Aluminium
  4. Zinc

Question 22

Why is aluminium extracted by electrolysis rather than by reduction with carbon?
  1. Aluminium is more reactive than carbon
  2. Aluminium oxide is a gas at room temperature
  3. Carbon cannot react with oxygen
  4. Electrolysis is always cheaper than carbon reduction

Question 23

In terms of oxygen, what is reduction?
  1. Loss of oxygen
  2. Gain of oxygen
  3. Gain of hydrogen ions only
  4. No change in oxidation state

Question 24

In terms of electrons, what is oxidation?
  1. Loss of electrons
  2. Gain of electrons
  3. Sharing electrons equally
  4. No transfer of electrons

Question 25

What are the products when hydrochloric acid reacts with magnesium?
  1. Magnesium chloride and hydrogen
  2. Magnesium chloride and oxygen
  3. Magnesium oxide and water
  4. Magnesium hydroxide only

Question 26

What are the products of an acid-carbonate reaction?
  1. Salt + water + carbon dioxide
  2. Salt + hydrogen only
  3. Salt + oxygen + water
  4. Salt + alkali only

Question 27

Which ionic equation represents neutralisation?
  1. \(\mathrm{H}^{+} + \mathrm{OH}^{-} \to \mathrm{H}_{2}\mathrm{O}\)
  2. \(\mathrm{H}^{+} + \mathrm{Cl}^{-} \to \mathrm{HCl}\)
  3. \(\mathrm{Na}^{+} + \mathrm{OH}^{-} \to \mathrm{NaOH}\)
  4. \(2\mathrm{H}^{+} + \mathrm{O}^{2-} \to \mathrm{H}_{2}\)

Question 28

Which method is used to make pure, dry copper sulfate from copper oxide and sulfuric acid?
  1. Add excess copper oxide, filter, then crystallise the filtrate
  2. Add exact amounts and evaporate to dryness directly
  3. Add copper oxide and distil off sulfuric acid
  4. Use titration with no filtration needed

Question 29

In electrolysis, reduction happens at the?
  1. Cathode
  2. Anode
  3. Electrolyte only
  4. External circuit only

Question 30

In electrolysis, oxidation happens at the?
  1. Anode
  2. Cathode
  3. Power supply only
  4. Salt bridge

Question 31

What are the products of electrolysis of molten lead bromide (PbBr2)?
  1. Lead at the cathode and bromine at the anode
  2. Lead oxide and hydrogen
  3. Lead and oxygen
  4. Hydrogen and bromine

Question 32

During electrolysis of aqueous sodium chloride (brine), what forms at the cathode?
  1. Hydrogen gas
  2. Sodium metal
  3. Chlorine gas
  4. Oxygen gas

Question 33

During electrolysis of aqueous sodium chloride (brine), what forms at the anode?
  1. Chlorine gas
  2. Hydrogen gas
  3. Sodium metal
  4. Water vapor only

Question 34

Which metal can displace copper from copper sulfate solution?
  1. Iron
  2. Silver
  3. Gold
  4. Platinum

Question 35

What does a lower pH value mean for an acid solution?
  1. Higher concentration of H+ ions
  2. Lower concentration of H+ ions
  3. Higher concentration of OH- ions
  4. No ions present

Question 36

Compared at the same concentration, a strong acid has a lower pH than a weak acid because it?
  1. Ionises more completely in water
  2. Contains larger molecules
  3. Always has more dissolved salt
  4. Has a higher boiling point

Question 37

What is the main purpose of a titration?
  1. To find the exact volume needed for neutralisation
  2. To separate a mixture by boiling point
  3. To measure gas pressure only
  4. To identify ions by flame color

Question 38

In electroplating with copper, the object to be plated is the?
  1. Cathode
  2. Anode
  3. Electrolyte
  4. Power supply

Question 39

What is the correct half equation for Al3+ ions at the cathode?
  1. \(\mathrm{Al}^{3+} + 3\mathrm{e}^{-} \to \mathrm{Al}\)
  2. \(\mathrm{Al} \to \mathrm{Al}^{3+} + 3\mathrm{e}^{-}\)
  3. \(\mathrm{Al}^{3+} \to \mathrm{Al} + 3\mathrm{e}^{-}\)
  4. \(\mathrm{Al} + 3\mathrm{e}^{-} \to \mathrm{Al}^{3+}\)

Question 40

Which equation shows reduction of copper(II) oxide by carbon?
  1. \(2\mathrm{CuO} + \mathrm{C} \to 2\mathrm{Cu} + \mathrm{CO}_{2}\)
  2. \(\mathrm{Cu} + \mathrm{CO}_{2} \to \mathrm{CuO} + \mathrm{C}\)
  3. \(2\mathrm{Cu} + \mathrm{O}_{2} \to 2\mathrm{CuO}\)
  4. \(\mathrm{CuO} + \mathrm{H}_{2}\mathrm{O} \to \mathrm{Cu(OH)}_{2}\)

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Review Chemical changes questions for Chemistry, with correct answers shown and coverage across acids, alkalis and neutralisation; reactivity series and displacement; electrolysis.

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