Extraction of Metals (Cambridge O Level Chemistry)

The position of aluminium in the reactivity series of metals is shown below.

magnesium
aluminium
zinc
copper

Aluminium is extracted by the electrolysis of its molten oxide.

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Aluminium reacts very slowly with aqueous copper(II) sulphate.

2Al(s) + 3CuSO₄(aq)  → Al₂(SO₄)₃(aq) + 3Cu(s)

Complete the following table by writing “reaction” or “no reaction” in the spaces provided.

Aluminium is an important metal with a wide range of uses.

Aluminium is obtained by the electrolysis of aluminium oxide dissolved in molten cryolite.

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Aluminium is used to make food containers because it resists corrosion.
Explain why it is not attacked by the acids in food.

Aluminium is used for overhead power (electricity) cables which usually have a steel core.

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Aluminium was first isolated in 1827 using sodium.

AlCl₃ + 3Na → Al + 3NaCl

Aluminium, obtained by this method, was more expensive than gold.

Suggest an explanation why aluminium was so expensive.

The modern method for extracting aluminium is the electrolysis of a molten electrolyte, aluminium oxide dissolved in cryolite. The aluminium oxide decomposes.

2Al₂O₃  → 4Al + 3O₂

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.......... O^2– → O₂ + ......... e^-

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The electrolysis of a molten electrolyte is one method of extracting a metal from its ore.

Other methods are the electrolysis of an aqueous solution and the reduction of the oxide by carbon.

Explain why these last two methods cannot be used to extract aluminium.

electrolysis of an aqueous solution ...................................................................................

using carbon .....................................................................................................................

Complete the labelling of the diagram.

The ions that are involved in the electrolysis are Al³⁺ and O^2-.
 

Give an explanation for each of the following.
 

Iron from the Blast Furnace is impure. It contains about 5% of impurities, mainly carbon, sulfur, silicon and phosphorus, which have to be removed when this iron is converted into steel.

Explain how the addition of oxygen and calcium oxide removes these impurities. Include an equation for a reaction of oxygen and a word equation for a reaction of calcium oxide in this process.

Mild steel is the most common form of steel. Mild steel contains a maximum of 0.3% of carbon.

High carbon steel contains 2% of carbon. It is less malleable and much harder than mild steel.

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Iron is extracted from its ore, hematite, in a blast furnace.

Substances added to the furnace are:

• Iron ore, hematite, containing impurities such as silica, SiO₂
• Air
• Coke, C
• Limestone, CaCO₃

Substances formed in the blast furnace are:

• Molten iron
• Molten slag
• Waste gases such as carbon dioxide

State the two functions of the coke used in the blast furnace.

Write an equation for the conversion of hematite, Fe₂O₃, to iron.

Explain how the silica impurity is removed and separated from the molten iron.

The molten iron from the furnace is impure. It contains impurities which include the element carbon. Explain how the carbon is removed. Include an equation in your answer.

Aluminium is obtained by the reduction of aluminium ions to aluminium atoms.

Write an ionic equation for the reduction of an aluminium ion to an aluminium atom.

The original method of extracting aluminium involved the reduction of aluminium chloride using the reactive metal sodium. Aluminium obtained by this method was very expensive due to the high cost of extracting sodium from sodium chloride.

In the modern method, aluminium is obtained by the electrolysis of aluminium oxide (alumina) dissolved in molten cryolite, Na₃AlF₆.

A major use of aluminium is the manufacture of pots and pans. One reason for this is its resistance to corrosion.

Iron from a blast furnace contains about 5% of the impurities – carbon, silicon, phosphorus and sulfur. Most of this impure iron is used to make steels, such as mild steel, and a very small percentage is used to make pure iron.

Iron from the blast furnace is impure. It contains 5% of impurities, mainly carbon, sulfur, silicon and phosphorus. Almost all of this impure iron is converted into the alloy, mild steel.

The oxides of carbon and sulfur are gases. The oxides of silicon and phosphorus are not.

Explain how these impurities are removed from the impure iron when it is converted into mild steel.

Iron is extracted from its ore, hematite, in the blast furnace.

The temperature inside the blast furnace can rise to 2000 °C. Write an equation for the exothermic reaction which causes this high temperature.

Carbon monoxide is formed in the blast furnace. This reduces the ore hematite, Fe₂O₃, to iron.

Explain why it is necessary to add limestone, calcium carbonate, to the blast furnace. Include an equation in your explanation.

Most of the iron from the blast furnace is converted into mild steel. A method of preventing the steel from rusting is coating it with zinc.

No one knows where iron was first isolated. It appeared in China, the Middle East and in Africa. It was obtained by reducing iron ore with charcoal.

Complete the following equation.

In 1705 Abraham Darby showed that iron ore could be reduced using coke in a blast furnace.

The formation of slag removes an impurity in the ore.

Write a word equation for the formation of the slag.

Stainless steel is an alloy of iron. It contains iron, other metals and about 0.5% of carbon.

One of the methods used to prevent iron or steel from rusting is to electroplate it with another metal, such as tin. Complete the following.

The anode is made of ............................................... 

The cathode is made of ............................................. 

The electrolyte is a solution of ...................................

A list of symbols and formulae is shown.

Which symbol or formula represents a compound produced by the thermal decomposition of calcium carbonate?

The diagram shows part of the structures of caesium chloride and carbon dioxide.

Explain why caesium is not extracted from caesium oxide by heating with carbon.

This question is about oxides.

The names of eight substances are given.

State which substance is the main constituent of bauxite.

Give the name of the process that is used to extract aluminium from aluminium oxide.

The table shows how easy it is to reduce four metal oxides with carbon.

Use the information in the table to put the four metals in order of their reactivity.

Put the least reactive metal first.

 

Zinc is extracted from an ore called zinc blende, which consists mainly of zinc sulfide, ZnS.
The zinc sulfide in the ore is first converted into zinc oxide.

Zinc oxide is converted into zinc. Zinc oxide and coke are fed into a furnace. Hot air is blown into the bottom of the furnace. The process is similar to the extraction of iron from iron oxide in a blast furnace.

Zinc has a melting point of 420 °C and a boiling point of 907 °C. The temperature inside the furnace is over 1000 °C.

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Rusting of steel can be prevented by coating the steel with a layer of zinc.

Explain, in terms of electron transfer, why steel does not rust even if the layer of zinc is scratched so that the steel is exposed to air and water.

When a sample of steel is added to dilute hydrochloric acid, an aqueous solution of iron(II) chloride, FeCl₂, is formed.
When a sample of rust is added to dilute hydrochloric acid, an aqueous solution of iron(III) chloride, FeCl₃, is formed.

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Solutions of iron(II) chloride and iron(III) chloride were added to solutions of potassium iodide and acidified potassium manganate(VII). The results are shown in the table.

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For centuries, iron has been extracted from its ore in the blast furnace. The world production of pig iron is measured in hundreds of million tonnes annually.

The following raw materials are supplied to a modern blast furnace.

• iron ore which is hematite, Fe₂O₃
• limestone which is calcium carbonate
• carbon in the form of coke
• air
  
  

Describe the essential reactions in the blast furnace. Each of the four raw materials must be mentioned at least once.

Give the equation for the reduction of hematite.

Each year, blast furnaces discharge millions of tonnes of carbon dioxide into the atmosphere. This will increase the percentage of atmospheric carbon dioxide.

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Separate: Chemistry and Extended Only

Aluminium is extracted by the electrolysis of a molten mixture of alumina, which is aluminium oxide, and cryolite.

Alumina is obtained from the main ore of aluminium.

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The ions which are involved in the electrolysis are Al³⁺ and O^2–. The products of this electrolysis are given on the diagram.

Explain how they are formed. Use equations where appropriate.

The uses of a metal are determined by its properties.

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Iron is extracted from its ore, hematite, in the blast furnace.

Describe the reactions involved in this extraction.

Include one equation for a redox reaction and one for an acid/base reaction.

Aluminium and iron are extracted from their ores by different methods.

Aluminium is extracted from its purified oxide ore by electrolysis.

What is the name of the ore of aluminium which consists mainly of aluminium oxide?

The electrodes are both made of the same substance.

Name this substance.

Aluminium oxide is dissolved in molten cryolite before it is electrolysed.

Give two reasons why aluminium oxide dissolved in molten cryolite is electrolysed rather than molten aluminium oxide alone.

Write the ionic equations for the reactions at the electrodes in this electrolysis.

Anode (positive electrode)

Cathode (negative electrode)

Iron is extracted from its oxide ore by reduction using carbon in a blast furnace.

What is the name of the ore of iron which consists mainly of iron(III) oxide?

Write balanced equations for the reactions occurring in the blast furnace which involve

Iron is extracted from the ore hematite in the Blast Furnace.

The coke reacts with the oxygen in the air to form carbon dioxide.

Limestone decomposes to form two products, one of which is calcium oxide.

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Iron and steel rust. Iron is oxidised to hydrated iron(III) oxide, Fe₂O₃.2H₂O, which is rust.

There are two electrochemical methods of rust prevention.

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