Chemistry Unit 2- Extraction of Metals

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  • Created by: FireDwarf
  • Created on: 11-03-14 20:45
How are metals commonly found?
Found in ores, containing minerals where the metal is combined with oxygen or sulphur.
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How do we therefore obtain the metal?
We need to remove the oxygen or sulphur.
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What are metals oxidation states as elements?
0
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In a metal oxide, is the metals oxidation state a + or a -? Therefore, to obtain just the element, what must occur?
It is positive oxidation state eg: Fe3+ . To form just the element ,reduction must occur Fe3+ + 3e- ---> Fe
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What usually occurs before reduction regarding sulfide ores and oxides?
The sulfide ores are converted to oxides by heating them in air.
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What is this proccess called?
Roasting.
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What are some options you can choose from for your reducing agent?
Coke because its cheaply obtained by heating coal in absence of air. Hydrogen is another option, hydrolysis, using more reactive metals.
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Why is coke bad for some reductions? (2 ANSWERS)
Because the tempertures needed for the reaction between coke and the metal are so high its expensive. Can also form carbides at high tempertures.
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What goes inside the blast furnace for iron reduction in a blast furnace.
Coke is used in a continuous proccess with a mixture of iron oxide and limestone.
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What are the reactions that occur?
Coke burns in hot air and causes formation of Co2. Co2 then reacts with more carbon to form CO. The Co is the reducing agent .
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What is produced?
Molten iron and carbon dioxide.
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Temperture inside blast furnace? How is the calcium carbonate removed?
Around 2000k via silicon oxdide reacting with calcium oxide (SiO2 + CaO ---> CaSiO3)/
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What is aluminium extracted from?
Purified bauxite ore.
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What is the proccess called?
The Hall- Héroult proccess.
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What is the first step of the proccess? What is the second step?
Extract the aluminium oxide from the bauxite ore. Dissolve the oxide in molten cryolite, Na3AlF6.
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Why is it dissolved?
To lower the melting point which makes it easier to extract.
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What are the two half equations for the electrolysis of Aluminium? Overall equation?
Aluminium formed at negative electrode 2Al(3+) + 6e ---> 2Al & 3O(2-) ---> 1 1/2 O2 + 6e- oxygen formed at postive electrode. OVERALL --> Al2O3---> 2Al + 1 1/2O2.
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What is each electrode made from?
Positive electrode- Carbon & Negative elctroduce steel casing.
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What is is the aluminium formed as ? What is the issue with the positve electrode? What is an overall issue?
A liquid & the oxgen produced at the postive electrode causes the carbon to burn off to produce Co2. Needs alot of electricity and therefore less profit.
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How is titatnium reduced? Negative points about this?
Using a more reactive metal such as sodium or magnesium. Very expensive as a result.
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Why cant we use coke?
Because it forms itanium carbide which makes the metal very brittle.
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What is the first proccess (it involves titanium oxide)? What is the ore titanium is found in called?
We need to convert titanium oxide into titanium chloride. Rutile is the ore and is turned into titanium chloride via reacting it with coke and chlroine.
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Equation?
TiO2(s) + 2C(s) + 2Cl2(g) --> TiCl4(l) + 2CO(g)
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Second step?
Reduction of the chloride with molten sodium or magnesium. This is completed in a inert argon atmosphere. TiCl4 + 4Na --> Ti + 4NaCl
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How is Tungsten reduced?
Using hydrogen. WO3 + 3H2 ---> W + 3H2O.
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What about other metals eg: Copper?
Unreactive metals can be extracted from ores by high temperture reduction with carbon/CO.
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Example with copper?
CuCo3 ---> (heat) CuO + Co2 ...... 2CuO + C ---> 2Cu + Co2
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What is another method for low grade ores?
Use of dilute acid in the presence of a bacterium. Useful on materials such as mining waste. Will produce a solution with Cu2+ ions. Using scrap metal, can then be reduced. Cu2+ + Fe --> Cu + Fe2+.
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Iron? Recycling and the enviroment?
Melted down and reformed. Reduces scrap iron. Can be used in extracting copper from mining waste (Cu2+ ions). Easilly extracted from other materials, doesnt cause Co2 directly (melting it).
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Al
Reduced energy compared to how much is needed to extract it. Reduces Co2 production.
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Card 2

Front

How do we therefore obtain the metal?

Back

We need to remove the oxygen or sulphur.

Card 3

Front

What are metals oxidation states as elements?

Back

Preview of the front of card 3

Card 4

Front

In a metal oxide, is the metals oxidation state a + or a -? Therefore, to obtain just the element, what must occur?

Back

Preview of the front of card 4

Card 5

Front

What usually occurs before reduction regarding sulfide ores and oxides?

Back

Preview of the front of card 5
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