Pearson Edexcel GCSE Combined Science · C4

Extracting metals and equilibria

Revision questions with answers for C4 Extracting metals and equilibria in Pearson Edexcel GCSE Combined Science (spec 1SC0). Practise with flashcards, a topic quiz, a random quiz across the course, 5 crosswords, or read every question and answer below.

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Question 1 · Spec C4.1
How can metal reactivity be compared experimentally?
Answer:
Compare reactions with water, dilute acids and solutions of other metal salts.
Question 2 · Spec C4.3
State the specified reactivity series, including carbon and hydrogen.
Answer:
Potassium, sodium, calcium, magnesium, aluminium, carbon, zinc, iron, hydrogen, copper, silver, gold.
Question 3 · Spec C4.3
What does greater metal reactivity imply about ion formation?
Answer:
The metal more readily loses electrons and forms positive ions.
Question 4 · Spec C4.1
What does faster hydrogen production with the same dilute acid usually indicate?
Answer:
Greater reactivity, provided surface area, amount and other conditions are comparable.
Question 5 · Spec C4.1
Why does copper not release hydrogen from dilute hydrochloric acid?
Answer:
Copper is below hydrogen in the reactivity series.
Question 6 · Spec C4.1
Why does magnesium displace copper from copper sulfate?
Answer:
Magnesium is more reactive and forms its own compound while copper is released.
Question 7 · Spec C4.1
If A displaces B but not C from salt solutions, what order is supported?
Answer:
C is more reactive than A, and A more reactive than B, assuming comparable valid tests.
Question 8 · Spec C4.2 · Higher only
Explain zinc-copper displacement using electrons.
Answer:
Zinc loses electrons to become Zn²⁺; Cu²⁺ gains electrons to become copper.
Question 9 · Spec C4.2 · Higher only
Write the ionic equation for zinc displacing copper.
Answer:
Zn + Cu²⁺ → Zn²⁺ + Cu.
Question 10 · Spec C4.5
Define oxidation and reduction using oxygen.
Answer:
Oxidation is gain of oxygen; reduction is loss of oxygen.
Question 11 · Spec C4.4
Why are most metals found as compounds in ores?
Answer:
They react with other substances rather than remaining as uncombined elements.
Question 12 · Spec C4.4
Why can gold occur uncombined in Earth's crust?
Answer:
It is very unreactive and resists forming compounds.
Question 13 · Spec C4.6
Why does extracting a metal from its oxide involve reduction?
Answer:
Oxygen is removed from the metal compound.
Question 14 · Spec C4.7
When can carbon commonly extract a metal from its oxide?
Answer:
When the metal is less reactive than carbon.
Question 15 · Spec C4.7
Why is aluminium extracted by electrolysis rather than carbon reduction?
Answer:
Aluminium is above carbon in the reactivity series, so carbon cannot reduce its oxide effectively.
Question 16 · Spec C4.7
Why can iron be obtained by heating its oxide with carbon?
Answer:
Iron is below carbon, so carbon can remove oxygen from the oxide.
Question 17 · Spec C4.7
Why must extraction cost be considered alongside chemical feasibility?
Answer:
An effective process may still be uneconomic because of energy, equipment or raw-material costs.
Question 18 · Spec C4.9
How does reactivity relate to resistance to oxidation?
Answer:
Less reactive metals generally resist oxidation more strongly than highly reactive metals.
Question 19 · Spec C4.8 · Higher only
What is phytoextraction or phytomining?
Answer:
Plants absorb metal compounds, are harvested and burned, leaving metal-rich ash for further processing.
Question 20 · Spec C4.8 · Higher only
What is bacterial extraction or bioleaching?
Answer:
Bacteria release metal compounds into a solution that can be processed to recover the metal.
Question 21 · Spec C4.8 · Higher only
How can copper be recovered from a biological extraction solution?
Answer:
By electrolysis or displacement using a more reactive metal such as iron.
Question 22 · Spec C4.8 · Higher only
Give a benefit and limitation of biological extraction.
Answer:
It can use low-grade sources with less excavation, but can be slow and still needs metal recovery steps.
Question 23 · Spec C4.10
How does recycling preserve metal resources?
Answer:
It reuses metal already extracted, reducing demand for new ore mining.
Question 24 · Spec C4.10
Why can recycling reduce energy use?
Answer:
Recovering and remelting metal often requires less energy than extracting it from ore.
Question 25 · Spec C4.10
Why is recycling not automatically impact-free?
Answer:
Collection, sorting, transport and reprocessing use energy and may produce waste.
Question 26 · Spec C4.10
How can recycling provide economic benefits?
Answer:
It can reduce raw-material and energy costs while creating collection and processing activity.
Question 27 · Spec C4.11
What stages belong in a product's life-cycle assessment?
Answer:
Obtaining raw materials, manufacture, use and final disposal, including relevant transport.
Question 28 · Spec C4.12
Why is comparing only manufacturing energy an incomplete assessment?
Answer:
Impacts during extraction, transport, use and disposal may change the overall comparison.
Question 29 · Spec C4.12
Why should life-cycle comparisons provide an equivalent service?
Answer:
Different lifetimes, capacities or reuse rates can otherwise make the comparison misleading.
Question 30 · Spec C4.12
A recycled route uses 15 MJ/kg versus 75 MJ/kg for extraction. Find the percentage saving.
Answer:
Saving = 60 MJ/kg; 60/75 × 100 = 80%.
Question 31 · Spec C4.12
Why can life-cycle assessments involve value judgements?
Answer:
Different harms may be weighted differently, and some impacts are difficult to quantify.
Question 32 · Spec C4.13
What is a reversible reaction?
Answer:
A reaction whose products can react to regenerate the reactants.
Question 33 · Spec C4.13
What does ⇌ indicate in an equation?
Answer:
The reaction can proceed in forward and reverse directions.
Question 34 · Spec C4.14
Define dynamic equilibrium.
Answer:
In a closed system, forward and reverse reactions continue at equal rates, so composition stays constant.
Question 35 · Spec C4.14
Why must the system remain closed for this equilibrium?
Answer:
Reactants and products must be retained instead of escaping.
Question 36 · Spec C4.14
Are reactant and product amounts necessarily equal at equilibrium?
Answer:
No. The reaction rates are equal; the amounts are constant but may differ.
Question 37 · Spec C4.15
State the balanced equation for ammonia formation.
Answer:
N₂ + 3H₂ ⇌ 2NH₃.
Question 38 · Spec C4.15
Where do the nitrogen and hydrogen for ammonia production come from?
Answer:
Nitrogen is extracted from air; hydrogen is obtained from natural gas.
Question 39 · Spec C4.16
State the specified Haber process conditions.
Answer:
About 450 °C, 200 atmospheres and an iron catalyst.
Question 40 · Spec C4.16
What is the catalyst's role in the Haber process?
Answer:
It increases reaction rate without being consumed overall.
Question 41 · Spec C4.17 · Higher only
State the principle used to predict an equilibrium's response to change.
Answer:
The system shifts in a direction that counteracts the imposed change.
Question 42 · Spec C4.17 · Higher only
How does adding a reactant affect equilibrium?
Answer:
It favours the direction that uses that reactant, forming more products.
Question 43 · Spec C4.17 · Higher only
How does removing product affect equilibrium?
Answer:
It favours product formation, replacing some of the removed product.
Question 44 · Spec C4.17 · Higher only
Which direction does higher temperature favour?
Answer:
The endothermic direction.
Question 45 · Spec C4.17 · Higher only
Which direction does lower temperature favour?
Answer:
The exothermic direction.
Question 46 · Spec C4.17 · Higher only
Ammonia formation is exothermic. What does increasing temperature do to equilibrium yield?
Answer:
It reduces the equilibrium proportion of ammonia by favouring the reverse reaction.
Question 47 · Spec C4.17 · Higher only
What does increasing pressure favour in a gas equilibrium?
Answer:
The side with fewer gas molecules, according to the balanced equation.
Question 48 · Spec C4.17 · Higher only
Why does high pressure favour ammonia in N₂ + 3H₂ ⇌ 2NH₃?
Answer:
It favours two product gas molecules over four reactant gas molecules.
Question 49 · Spec C4.17 · Higher only
What if both sides contain the same number of gas molecules?
Answer:
A pressure change alone does not shift the equilibrium position.
Question 50 · Spec C4.17 · Higher only
Does a catalyst change the equilibrium composition?
Answer:
No. It speeds both directions, allowing equilibrium to be reached sooner.

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