Qualification > Sciences
CHEMISTRY.. SEPERATING TECHINQUES quiz on TUESDAY.. help
Vin:
Thank you GG for the links.
Zinc, copper and iron coming up shorty.
Vin:
Extraction of Zinc.
Zinc ore ---> zinc blende (zinc sulfide - ZnS)
First, it is roasted in air to give zinc oxide:
2ZnS + 3O2 ---> 2ZnO + 2SO2
Then the oxide is reduced in one of the following ways:
Method 1. Using carbon monoxide:
ZnO + CO --> Zn + CO2
The final mixture contains zinc and a slag of impurities. The zinc is separated from it by fractional distillation.
Method 2. Electrolysis
For this, zinc oxide is dissloved in sufuric acid to give zinc sulfate (salt) and water [Acid + Base -> Salt and Water]
Why this is done? For electrolysis, the general principle is the electrolyte (the solution in container) has to conduct electricity - so for metals or metal oxides it has to either be in molten form or their salt solution. Zinc oxide is a (basic) oxide and is insoluble in water and the melting point is very high. So the salt solution is obtained in order to carry put the electrolysis. So, not necessarily sulfuric acid must be used, any acid for that matter.
At cathode:
Zn2+ + 2e- ---> Zn (s)
This zinc is scraped off the cathode. This method is preferable as it gives zinc of very high purity.
Vin:
Extraction of Copper.
Copper ore ---> malachite (Copper (II) carbonate - CuCO3)
The reaction takes place in two stages :
Stage 1 - The malachite decomposes :
CuCO3 (s) ---> CuO (s) + CO2 (g)
Stage 2 - The copper (II) oxide is reduced by carbon :
2CuO (s) + C (s) ---> 2Cu (s) + CO2(g)
This copper is then purified by electrolysis.
Vin:
For extraction of iron, I shall post a picture from my textbook - explains it really well, after my scanner or even the webcam decide to function. :P ;)
OK not working out really well so here are the notes :
Extraction of iron.
Iron ore ---> haematite (Iron (II) Oxide - Fe2O3)
[If image too small - Right-click > View image]
yeah so as you can see the extraction of Fe takes place in a blast furnace.
Raw materials used to put at the top.
>Iron ore (Fe2O3)
>Coke (Main source for Carbon needed for the reduction process)
>Limestone (needed to remove the impurities in the form of 'slag')
Steps in which the extraction is conducted :
1. Iron ore, coke and limestone are fed into the top of the blast furnace.
2. Hot air blasted up the furnace from the bottom.
3. Oxygen from the sir reacts with coke to from carbon dioxide.
C (s) + O2 (g) ---> CO2 (g)
4.Carbon dioxide reacts with more coke to form carbon monoxide
CO2 (g) + C (s) ---> 2CO (g)
5.Carbon monoxide is a reducing agent.
Iron (II) oxide is reduced to iron :
Fe2O3 (s) + 3CO (g) ---> 2Fe (l) + 3CO2 (g)
6. Dense molten iron runs to the bottom of the furnace and is run off. There are many impurities in iron ore. The limestone helps to remove these shown in steps 7 and 8.
7. Limestone is broken down by heat to calcium oxide :
CaCO3 (s) ---> CaO (s) + CO2 (g)
8. Calcium oxide reacts with impurities like sand (silicon dioxide) to form a liquid called 'slag':
CaO (s) + SiO2 (g) ---> CaSiO3 (l)
(calcium silicate)
the liquid slag falls to the bottom of the furnace and is tapped off.
The overall reaction :
2Fe2O3 (s) + 3C ---> 4Fe + 3CO2
Reduction reaction stages :
Stage 1 - The coke reacts with oxygen blasted into the furnace :
C (s) + O2 (g) ---> CO2 (g)
Stage 2 - The carbon dioxide is reduced by unreacted coke to form carbon monoxide :
CO2 (g) + C (s) ---> 2CO (g)
Stage 3 - The iron (iii) oxide is reduced by the carbon monoxide to iron :
Fe2O3 (s) + 3CO (g) ---> 2Fe (s) + 3CO2 (g)
Vin:
--- Quote from: wanabeastarstudent on September 29, 2010, 11:55:38 am --- ??? hey.. well i got a quiz on tuesday on thse things from the past year but i didnt study last year so can u help me wiv these topic n post websites plz?
*state of matter
*seperating techniques and mixtures
*atomic structure
*bonding (metallic,covalent,ironic and macromolecular)
thanks so much
and im doing extraction of iron (Fe), aluminuim and zinc do u have any websites? cuz i started skwl late so i missed out thanks :P u guys are great :) :-*please help
--- End quote ---
OK, here are a couple of ppts. The rest I'll try to type out notes after a while.
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