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

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

Question 2

Why is cryolite added during aluminium extraction?
  1. Lowers the operating temperature
  2. Oxidises aluminium at the anode
  3. Removes carbon dioxide from the cell
  4. Increases aluminium oxide's melting point

Question 3

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

Question 4

What happens to an element's oxidation state during oxidation?
  1. It increases
  2. It decreases
  3. It stays unchanged
  4. It becomes zero

Question 5

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

Question 6

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

Question 7

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 8

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 9

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

Question 10

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

Question 11

What forms at the cathode during electrolysis of molten lead bromide (PbBr2)?
  1. Lead
  2. Bromine
  3. Oxygen
  4. Hydrogen

Question 12

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 13

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

Question 14

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

Question 15

What does a lower pH mean for an acid solution?
  1. Higher \(\mathrm{H^+}\) concentration
  2. Lower \(\mathrm{H^+}\) concentration
  3. Higher \(\mathrm{OH^-}\) concentration
  4. Lower total ion concentration

Question 16

Which property makes a strong acid produce more \(\mathrm{H^+}\) than a weak acid?
  1. More complete ionisation
  2. More hydrogen atoms per molecule
  3. Lower relative formula mass
  4. Higher boiling point

Question 17

Which quantity does a titration determine precisely?
  1. Neutralising volume
  2. Reaction temperature change
  3. Gas volume
  4. Rate from mass loss

Question 18

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

Question 19

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 20

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. \(\mathrm{CuO} + \mathrm{H}_{2}\mathrm{O} \to \mathrm{Cu(OH)}_{2}\)

Question 21

What is oxidation in terms of electrons?
  1. Loss of electrons
  2. Gain of electrons
  3. Gain of protons
  4. Loss of neutrons

Question 22

What is reduction in terms of electrons?
  1. Gain of electrons
  2. Loss of electrons
  3. Gain of neutrons
  4. Loss of atoms

Question 23

What is electrolysis?
  1. Decomposing an ionic compound with electricity
  2. Generating electricity from a chemical reaction
  3. Separating dissolved solids by filtration
  4. Dissolving electrodes without a current

Question 24

Why must an ionic compound be molten or dissolved for electrolysis?
  1. Its ions need to be able to move
  2. The compound needs to become a gas
  3. The ions need to become neutral
  4. The electrode needs to melt

Question 25

What happens to positive ions at the negative electrode during electrolysis?
  1. Positive ions gain electrons
  2. Negative ions gain electrons
  3. Positive ions lose electrons
  4. Electrons leave the electrolyte

Question 26

What happens to negative ions at the positive electrode?
  1. Negative ions lose electrons
  2. Negative ions gain electrons
  3. Positive ions lose electrons
  4. Positive ions gain electrons

Question 27

What does the reactivity series predict?
  1. Whether one metal displaces another
  2. Metal melting-point order
  3. Metal density order
  4. Metal conductivity order

Question 28

Which aluminium property means it needs electrolysis for extraction?
  1. More reactive than carbon
  2. Low density
  3. Good electrical conductor
  4. Protective oxide layer

Question 29

Which acid ion is replaced when a salt forms?
  1. Hydrogen ions
  2. Hydroxide ions
  3. Oxide ions
  4. Metal ions

Question 30

Which apparatus delivers a measured variable volume in a titration?
  1. Burette
  2. Volumetric pipette
  3. Volumetric flask
  4. Measuring cylinder

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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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