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IGCSE Chemistry > extraction of metals > Flashcards

extraction of metals Flashcards

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1
Q

what type of process if ore is an oxide of metal

A

reduction (loses oxygen)

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2
Q

what elements are extracted by electrolysis

A

potassium, sodium, lithium, calcium, magnesium, aluminium

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3
Q

what types of metals are extracted by heating with reducing agent and what type of reducing agent is

A

zinc, iron
carbon or carbon monoxide

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4
Q

what are elements that are found as pure

A

copper, silver, gold
copper may be extracted from its ore by heating with carbon/hydrogen

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5
Q

raw materials that are added into the top of blast furnace

A

iron ore (hematite), coke (impure form of carbon) and limestone.

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6
Q

where is hot air blown in from in a blast furnace

A

bottom

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7
Q

what happens in zone 1 of blast furnace

A
  • coke burns in the hot air forming CO2. exothermic, so heats up the furnace.
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8
Q

what happens in zone 2 of blast furnace

A
  • at high temps, more coke reacts with CO2 forming CO (reduction)
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9
Q

what happens in zone 3 of the blast furnace

A
  • CO reduces iron (III) oxide in the iron ore to form iron (lose oxygen). Iron melts and collects at the bottom of the furnace where it is tapped off
  • limestone (calcium carbonate) is added to furnace to remove impurities in ore (calcium carbonate thermally decomposes to form calcium oxide)
  • calcium oxide formed reacts with silicon dioxide (impurity in iron ore) to form calcium silicate
  • melts and collects as molten slag floating on top of the molten iron, which is tapped off seperately
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10
Q

equation for burning of coke to CO2

A

C (s) + O2 (g) -> CO2 (g)

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11
Q

reduction of CO2 to CO

A

CO2 (g) + C (s) -> 2CO (g)

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12
Q

reduction of iron (III) oxide by CO

A

Fe2O3 (s) + 3CO (g) -> 2Fe (l) + 3CO2 (g)

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13
Q

thermal decomposition of calcium carbonate (limestone) to produce calcium oxide

A

CaCO3 (s) -> CaO (s) + CO2 (g)

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14
Q

formation of slag

A

CaO (s) + SiO2 (s) -> CaSiO3 (l)

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15
Q

what is iron ore called

A

hematite

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16
Q

what is aluminium ore called

A

bauxite (contains aluminiun oxide)

17
Q

why cant aluminium be extracted by reduction using carbon

A

it is higher in the reactivity series

18
Q

what is aluminium extracted by

A

electrolysis

19
Q

process of aluminium extraction by electrolysis

A
  • bauxite purified to produce aluminium oxide Al2O3
  • aluminium oxide dissolved in molten cryolite
  • mixture placed in electrolysis cell
  • graphite lining acts as negative electrode with several large graphite blocks as positive electrode
  • at cathode: aluminium ions are reduced, molten aluminium forms at bottom of the cell, molten aluminium is siphoned off from time to time and fresh aluminium oxide is added to the cell
  • at anode: oxide ions are oxidised, oxygen produced at anode
20
Q

what is the use of cryolite in aluminium extraction

A

aluminium oxide has mp of over 2000C which would use alot of energy and be very expensive. the resulting mixture has a lower melting point without interfering with reaction

21
Q

what is electroylsis cell made of in aluminium extraction

A

made from steel, lined with graphite

22
Q

what is ionix half equation for aluminium at cathode

A

Al+3 + 3e- -> Al

23
Q

What is ionic half equation for oxidation of oxide ions

A

2O-2 -> O2 + 4e-

24
Q

what is overall equation for reaction during aluminium extraction

A

2Al2O3 -> 4Al + 3O2

25
Q

what happens to the graphite in the anodes in aluminium extraction

A

carbon in graphite reacts with oxygen to produce CO2, resulting in anode wearing away and having to be replaced regularly

26
Q

what is bad about extraction of aluminium by electroylsis

A

alot of electricity required, so major expense

27
Q

what is a metal displacement

A

when a more reactive metal displaces a less reactive metal from its compound

28
Q

2 examples of metal displacement

A
  • reacting metal with metal oxide (by heating)
  • reacting a metal with an aqueous solution of a metal compound

IGCSE Chemistry (12 decks)

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