20290 - extraction of metals
TRANSCRIPT
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Extraction ( 提煉 ) of Metals from Metal Ores ( 礦石 )
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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)
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Reactivities ( 活潑性 ) and extraction ( 提煉 ) of Metals
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reactivitydecreases
Least reactive
Most reactive
Group I metal
Group II metal
Group III metal
Precious metal
Transition metal
PotassiumSodiumCalciumMagnesiumAluminiumZincIronLeadCopperMercurySilverGold
KNaCaMgAlZnFePbCuHgAgAu
Reactivity Series of metals
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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-
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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
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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
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Thermal decomposition of metal oxide
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Thermal decomposition of metal oxide Example
Thermal decomposition ofmercury(II) oxide
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Thermal decomposition of metal oxide
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Thermal decomposition of metal oxide
Word equationmercury(II) oxide
Unbalanced chemical equation
Balanced chemical equation
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Thermal decomposition of metal oxide
Word equationmercury(II) oxide mercury + oxygen
Unbalanced chemical equation
Balanced chemical equation
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Thermal decomposition of metal oxide
Word equationmercury(II) oxide mercury + oxygen
Unbalanced chemical equationHgO(s) Hg(l) + O2(g)
Balanced chemical equation
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Thermal decomposition of metal oxide
Word equationmercury(II) oxide mercury + oxygen
Unbalanced chemical equationHgO(s) Hg(l) + O2(g)
Balanced chemical equation2HgO(s) 2Hg(l) + O2(g)
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Reduction of metal oxide by C(graphite), CO(g), H2(g)
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Reduction of metal oxide by C(graphite), CO(g), H2(g)
ExampleReduction copper(II) oxide by graphite
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Reduction of metal oxide by C(graphite), CO(g), H2(g)
Word equationcopper(II) oxide + carbon
Unbalanced chemical equation
Balanced chemical equation
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Reduction of metal oxide by C(graphite), CO(g), H2(g)
Word equationcopper(II) oxide + carbon
copper + carbon dioxide
Unbalanced chemical equation
Balanced chemical equation
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Reduction of metal oxide by C(graphite), CO(g), H2(g)
Word equationcopper(II) oxide + carbon
copper + carbon dioxide
Unbalanced chemical equation CuO(s) + C(s) Cu(s) + CO2(g)
Balanced chemical equation
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Reduction of metal oxide by C(graphite), CO(g), H2(g)
Word equationcopper(II) oxide + carbon
copper + carbon dioxide
Unbalanced chemical equation CuO(s) + C(s) Cu(s) + CO2(g)
Balanced chemical equation2CuO(s) + C(s) 2Cu(s) + CO2(g)
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Reduction of metal oxide by C(graphite), CO(g), H2(g)
ExampleReduction copper(II) oxide by CO
Town gas consists of mainly H2(g) and CO(g).
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Reduction of copper(II) oxide by town gas
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Reduction of metal oxide by C(graphite), CO(g), H2(g)
Word equationcopper(II) oxide + carbon monoxide
Unbalanced chemical equation
Balanced chemical equation
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Reduction of metal oxide by C(graphite), CO(g), H2(g)
Word equationcopper(II) oxide + carbon monoxide
copper + carbon dioxide
Unbalanced chemical equation
Balanced chemical equation
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Reduction of metal oxide by C(graphite), CO(g), H2(g)
Word equationcopper(II) oxide + carbon monoxide
copper + carbon dioxide
Unbalanced chemical equation CuO(s) + CO(g) Cu(s) + CO2(g)
Balanced chemical equation
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Reduction of metal oxide by C(graphite), CO(g), H2(g)
Word equationcopper(II) oxide + carbon monoxide
copper + carbon dioxide
Unbalanced chemical equation CuO(s) + CO(g) Cu(s) + CO2(g)
Balanced chemical equationCuO(s) + CO(g) Cu(s) + CO2(g)
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Reduction of metal oxide by C(graphite), CO(g), H2(g)
What precautions ( 防範 ) have to be taken in this experiment ?
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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.
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Why should these precautions be taken ?
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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.
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Reduction of metal oxide by C(graphite), CO(g), H2(g)
ExampleReduction of copper(II) oxide by Hydrogen
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Reduction of copper(II) oxide by H2(g)
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Reduction of copper(II) oxide by H2(g)
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Reduction of copper(II) oxide by H2(g)
Word equationcopper(II) oxide + hydrogen
Unbalanced equation
Balanced equation
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Reduction of copper(II) oxide by H2(g)
Word equationcopper(II) oxide + hydrogen
copper + water
Unbalanced equation
Balanced equation
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Reduction of copper(II) oxide by H2(g)
Word equationcopper(II) oxide + hydrogen
copper + water
Unbalanced equationCuO(s) + H2(g) Cu(s) + H2O(g)
Balanced equation
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Reduction of copper(II) oxide by H2(g)
Word equationcopper(II) oxide + hydrogen
copper + water
Unbalanced equationCuO(s) + H2(g) Cu(s) + H2O(g)
Balanced equationCuO(s) + H2(g) Cu(s) + H2O(g)
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What is observed when town gas is passed over heated copper(II) oxide in a combustion tube ? Explain your answer and write appropriate equations.
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Reduction of metal oxide by C(graphite), CO(g), H2(g)
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.
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What do graphite, carbon monoxide and hydrogen gas shared in common in the extraction of metals from metal oxides ?
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Reduction of metal oxide by C(graphite), CO(g), H2(g)
Reducing power
C(graphite) > CO(g) > H2(g)
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Extraction of Iron(Reduction of iron ore by carbon)
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Write the equations involved in the extraction of iron from iron(III) oxide.
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Electrolysis of molten ore
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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)
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Electrolysis of molten ore
Extraction of aluminium from aluminium oxide (alumina)
)(2)()(32 342 gliselectrolys
l OAlOAl
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Extraction of aluminium
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Electrolysis of molten ore
Extraction of sodium from sdoium chloride (common salt)
)(2)()( 22 gliselectrolys
l ClNaNaCl
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Extraction of sodium
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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.
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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
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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.