The method chosen to extract a metal depends on the position of the metal in the reactivity series. Fig. 2.1 shows part of the reactivity series; carbon is ...
Question 1 Report
The method chosen to extract a metal depends on the position of the metal in the reactivity series. Fig. 2.1 shows part of the reactivity series; carbon is included in brackets. Bracket A and bracket B mark two ranges of metals.
Fig. 2.1
Table 2.1 lists four metals and how each is obtained.
| Metal | Main extraction method |
|---|---|
| potassium | |
| zinc | |
| iron | reduction in a furnace |
| gold |
(a) State the general method used to extract the metals in bracket A. [1]
(b) Explain, in terms of reactivity, why the metals in bracket A cannot be extracted by heating their oxides with carbon. [2]
(c) Complete Table 2.1 by giving the main extraction method for potassium, zinc and gold. [3]
(d) Name the substance normally used to reduce the metals in bracket B from their oxides. [1]
(e) Zinc oxide is reduced by this substance. Write the symbol equation for the reaction of zinc oxide with carbon to form zinc and carbon monoxide. [2]
(f) State the meaning of the term ore. [1]
(g) Suggest why gold is found in the ground as the uncombined metal. [2]
Answer Details
This question links the reactivity series to the method used to extract each metal.
(a) The metals in bracket A (the most reactive, above carbon) are extracted by electrolysis of the molten compound / oxide [1].
(b) Carbon cannot be used for bracket A because [2]: these metals are more reactive than carbon [1], so carbon cannot remove the oxygen from (cannot reduce) their oxides [1]. A more reactive metal holds onto its oxygen too strongly for carbon to take it.
(c) Completing Table 2.1, [1] each: potassium is above carbon so electrolysis; zinc is below carbon so reduction (heating) with carbon; gold is so unreactive it is found native and simply dug up (no chemical extraction).
| Metal | Main extraction method |
|---|---|
| potassium | electrolysis |
| zinc | reduction (heating) with carbon |
| iron | reduction in a furnace |
| gold | found native / dug up as the metal |
(d) The substance normally used to reduce the bracket B metals from their oxides is carbon (coke) [1].
(e) Zinc oxide reacts with carbon to give zinc and carbon monoxide:
ZnO + C → Zn + CO
Award [1] for correct formulae and [1] for balancing (1 Zn, 1 C and 1 O on each side).
(f) An ore is a naturally occurring rock or mineral from which a metal can be extracted [1].
(g) Gold is found as the uncombined (native) metal because [2]: it is very unreactive and low in the reactivity series [1], so it does not react with other substances and stays as the free metal rather than forming a compound [1].
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