20290 - Extraction of Metals

Extraction ( 提煉 ) of Metals from Metal Ores ( 礦石 )

Integrated Chemistry Today Book 1A, 2nd Edition

10.9 Extraction of metals(pg 158-161)10.10 What determines the reactivity of a metal ?(pg 161-162)

Reactivities ( 活潑性 ) and extraction ( 提煉 ) of Metals

reactivitydecreases

Least reactive

Most reactive

Group I metal

Group II metal

Group III metal

Precious metal

Transition metal

PotassiumSodiumCalciumMagnesiumAluminiumZincIronLeadCopperMercurySilverGold

KNaCaMgAlZnFePbCuHgAgAu

Reactivity Series of metals

Reactivity Series of metals Reactivity of a metal is depending on its readiness

( 意願 ) to lose its outermost electrons.i.e. A more reactive metal loses its electron more readily ( 願意地 ).

Just the opposite ( 相反 ), the metal ion of a more reactive metal gains electrons less readily.

M d M+ + e-lose e-

gain e-

Extraction ( 提煉 ) of Metals Most metals exist only in combined for

m (i.e. compound) in nature ( 自然界 ) in form of ions.

Extraction of pure metals involves the reduction ( 還原 ) of metal ions in the ore to metal atoms.

M d M+ + e-lose e-

gain e-

in the orein the extractedmetal

Extraction ( 提煉 ) of Metals Thermal decomposition ( 熱分解 ) of me

tal oxide – for metals less reactive than Hg

Reduction ( 還原作用 ) of metal oxide by carbon – for metals less reactive than Zn

Electrolysis ( 電解 ) of molten salt – for all metals

Thermal decomposition of metal oxide

Thermal decomposition of metal oxide Example

Thermal decomposition ofmercury(II) oxide



Word equationmercury(II) oxide

Unbalanced chemical equation

Balanced chemical equation


Word equationmercury(II) oxide mercury + oxygen





Unbalanced chemical equationHgO(s) Hg(l) + O2(g)




Unbalanced chemical equationHgO(s) Hg(l) + O2(g)

Balanced chemical equation2HgO(s) 2Hg(l) + O2(g)

Reduction of metal oxide by C(graphite), CO(g), H2(g)


ExampleReduction copper(II) oxide by graphite


Word equationcopper(II) oxide + carbon





copper + carbon dioxide






Unbalanced chemical equation CuO(s) + C(s) Cu(s) + CO2(g)





Unbalanced chemical equation CuO(s) + C(s) Cu(s) + CO2(g)

Balanced chemical equation2CuO(s) + C(s) 2Cu(s) + CO2(g)


ExampleReduction copper(II) oxide by CO

Town gas consists of mainly H2(g) and CO(g).

Reduction of copper(II) oxide by town gas


Word equationcopper(II) oxide + carbon monoxide











Unbalanced chemical equation CuO(s) + CO(g) Cu(s) + CO2(g)





Unbalanced chemical equation CuO(s) + CO(g) Cu(s) + CO2(g)

Balanced chemical equationCuO(s) + CO(g) Cu(s) + CO2(g)


What precautions ( 防範 ) have to be taken in this experiment ?

What precautions ( 防範 ) have to be taken in this experiment ?

The experiment should be carried out in a fume cupboard ( 煙櫃 ).

The tube should be flushed ( 沖 ) with town gas thoroughly ( 透徹地 ) before the flame is lighted up.

At the end of the experiment, the town gas supply should only be cut off after the copper obtained is cooled down.

Why should these precautions be taken ?

Why should these precautions be taken ? Town gas used is toxic. If air is present, the CO and O2

mixture is explosive. To prevent re-oxidation of copper to

copper(II) oxide in air when the copper is hot.


ExampleReduction of copper(II) oxide by Hydrogen

Reduction of copper(II) oxide by H2(g)



Word equationcopper(II) oxide + hydrogen

Unbalanced equation

Balanced equation



copper + water

Unbalanced equation

Balanced equation



copper + water

Unbalanced equationCuO(s) + H2(g) Cu(s) + H2O(g)

Balanced equation



copper + water

Unbalanced equationCuO(s) + H2(g) Cu(s) + H2O(g)

Balanced equationCuO(s) + H2(g) Cu(s) + H2O(g)

What is observed when town gas is passed over heated copper(II) oxide in a combustion tube ? Explain your answer and write appropriate equations.


Reduction ( 還原作用 )- Removal of oxygene.g. CuO(s) + H2(g) Cu(s) + H2O(g)Black copper(II) oxide is reduced to reddish brown copper by hydrogen.

Oxidation ( 氧化作用 )- Addition of oxygene.g. 2Cu(s) + O2(g) 2CuO(s)Reddish brown copper is oxidized to black copper(II) oxide by oxygen.

What do graphite, carbon monoxide and hydrogen gas shared in common in the extraction of metals from metal oxides ?


Reducing power

C(graphite) > CO(g) > H2(g)

Extraction of Iron(Reduction of iron ore by carbon)

Write the equations involved in the extraction of iron from iron(III) oxide.

Electrolysis of molten ore


The cations in the molten ore will receive electrons from the cathode and become the metal atom.

Metal ion + electron Metale.g. Na+

(l) + e- Na(l)

Mg2+(l) + 2e- Mg(l)

Al3+(l) + 3e- Al(l)


Extraction of aluminium from aluminium oxide (alumina)

)(2)()(32 342 gliselectrolys

l OAlOAl

Extraction of aluminium


Extraction of sodium from sdoium chloride (common salt)

)(2)()( 22 gliselectrolys

l ClNaNaCl

Extraction of sodium

Extraction ( 提煉 ) of Metals It is more difficult to extract a

reactive metal than a non-reactive metal from the ore.

For K, Na, Ca, Mg and Al, they can only be prepared by electrolysis of

the molten ore.

Extraction from the orePotassium (K)

Electrolysis of molten oreSodium (Na)

Calcium (Ca)

Magnesium (Mg)

Aluminium (Al)Zinc (Zn)

Heating with graphiteIron (Fe)

Lead (Pb)Copper (Cu)

Mercury (Hg)Heating alone

Silver (Ag)

Gold (Au) Occurs naturally

Conversion of sulphide ore to oxide ore Sulphide ore and oxide are the 2 com

mon metal ores exist in nature. In the extraction of metal from sulphide ore, the metal sulphide is first roasted ( 燒 ) in air to convert to oxide and sulphur dioxide first. Write an equation for the conversion of zinc sulphide to zinc oxide.

20290 - Extraction of Metals

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