How is the method of extracting a metal decided by its reactivity?
How the reactivity of a metal determines its extraction method, the extraction of iron by reduction with carbon in the blast furnace, and why reactive metals are extracted by electrolysis.
A CCEA GCSE Chemistry answer on the extraction of metals, covering how a metal's position in the reactivity series sets its extraction method, the reduction of iron oxide with carbon in the blast furnace, and why metals above carbon are extracted by electrolysis.
Reviewed by: AI editorial process; not yet individually human-reviewed
Have a quick question? Jump to the Q&A page
Jump to a section
What this dot point is asking
CCEA wants you to explain how a metal's reactivity decides its method of extraction, describe the extraction of iron by reduction with carbon in the blast furnace, and explain why reactive metals such as aluminium are extracted by electrolysis.
Reactivity decides the method
Carbon sits in the series as a dividing line: it can only displace oxygen from the oxides of metals less reactive than itself.
Extracting iron in the blast furnace
The carbon monoxide is the main reducing agent, removing the oxygen from the iron oxide. Molten iron runs to the bottom. The limestone removes sandy impurities by forming a molten slag that floats on the iron and is tapped off separately.
Why reactive metals need electrolysis
This is why aluminium, although abundant, was expensive until electrolysis became practical: carbon simply cannot reduce aluminium oxide. Electrolysis uses a lot of electrical energy, which is why extracting reactive metals is costly.
Worked example
Examples in context
- Example 1. The cost of aluminium
- Recycling aluminium uses only a fraction of the energy of extracting it by electrolysis, which is why aluminium recycling is so worthwhile. The high energy cost comes directly from aluminium being above carbon in the reactivity series.
- Example 2. Iron for steel
- The blast furnace produces huge quantities of iron that are then converted into steel for construction and vehicles. The whole steel industry depends on the cheap reduction of iron ore by carbon, possible because iron sits below carbon.
- Example 3. Why gold was the first metal used
- Gold is so unreactive that it occurs native, as nuggets of the pure element, which is why ancient people could use it long before they could extract any other metal. Its position at the very bottom of the reactivity series, needing no chemical extraction at all, explains its early use in jewellery and coinage.
The bigger picture: energy and the environment
Extraction methods carry an environmental cost that follows the reactivity series. Reducing iron with carbon releases large amounts of carbon dioxide, contributing to global warming, while electrolysis of reactive metals consumes huge quantities of electricity. This is one reason recycling is so valuable: recycling aluminium uses only about five percent of the energy needed to extract it fresh. CCEA expects you to link the choice of extraction method not only to reactivity but also to the energy used and the environmental impact, which is why these calculations matter beyond the chemistry itself.
Try this
Q1. State the method used to extract a metal more reactive than carbon. [1 mark]
- Cue. Electrolysis of the molten compound.
Q2. Name the main reducing agent in the blast furnace. [1 mark]
- Cue. Carbon monoxide.
Exam-style practice questions
Practice questions written in the style of CCEA exam questions on this dot point, with worked answer explainers. The year tag is the paper they imitate, not the source.
CCEA 20194 marksExplain why iron can be extracted from its ore by heating with carbon, but aluminium cannot, and state how aluminium is extracted instead.Show worked answer →
Markers want the link to the reactivity series.
Carbon can only remove oxygen from (reduce) the oxide of a metal that is less reactive than carbon. Iron is below carbon in the reactivity series, so carbon is reactive enough to reduce iron oxide to iron.
Aluminium is above carbon in the reactivity series, so carbon is not reactive enough to remove the oxygen from aluminium oxide.
Aluminium is therefore extracted by electrolysis of molten aluminium oxide instead.
Markers reward iron below carbon (so carbon reduces it), aluminium above carbon (so carbon cannot), and electrolysis for aluminium.
CCEA 20214 marksIn the blast furnace, describe how iron(III) oxide is reduced to iron, including the role of carbon monoxide. Write the equation for the reduction by carbon monoxide.Show worked answer →
The marks are for the carbon monoxide route and a correct equation.
In the blast furnace, hot air burns the coke (carbon) to form carbon dioxide, which reacts with more coke to form carbon monoxide.
The carbon monoxide is the main reducing agent: it removes the oxygen from the iron(III) oxide, reducing it to molten iron and forming carbon dioxide:
Markers reward carbon monoxide forming and acting as the reducing agent, and the balanced equation reducing iron(III) oxide to iron.
Related dot points
- The reactivity series of metals, the reactions of metals with water and acid, and displacement reactions of metals with metal salt solutions.
A CCEA GCSE Chemistry answer on the reactivity series, covering how metals are ranked by their reactions with water and acid, the order of the common metals, and how a more reactive metal displaces a less reactive one from its salt solution.
- Oxidation and reduction defined in terms of oxygen and of electrons (OIL RIG), identifying redox in displacement and other reactions, and writing half-equations.
A CCEA GCSE Chemistry answer on redox reactions, covering oxidation and reduction defined by the gain and loss of oxygen and of electrons (OIL RIG), how to identify oxidation and reduction in displacement and other reactions, and how to write half-equations.
- Electrolysis of molten ionic compounds and of aqueous solutions including brine, predicting the products at each electrode, and writing electrode half-equations.
A CCEA GCSE Chemistry answer on electrolysis, covering how molten ionic compounds and aqueous solutions are split by an electric current, the rules for predicting the products at the cathode and anode including the electrolysis of brine, and writing electrode half-equations.
- The rusting of iron and the conditions needed, and methods of preventing corrosion including barrier methods, galvanising and sacrificial protection.
A CCEA GCSE Chemistry answer on corrosion, covering the rusting of iron, the conditions of water and oxygen needed, and the methods used to prevent corrosion including barrier methods, galvanising and sacrificial protection.
- Metallic bonding as positive ions in a sea of delocalised electrons, how this explains the properties of metals, and why alloys are harder than the pure metal.
A CCEA GCSE Chemistry answer on metallic bonding, covering the model of positive ions in a sea of delocalised electrons, how it explains conductivity, malleability and high melting points, and why alloys are harder than the pure metal.
Sources & how we know this
- CCEA GCSE Chemistry specification (1110) — CCEA (2017)