http://www.xtremepapers.com/papers/...l O Level/Chemistry (5070)/5070_s11_qp_21.pdf
Can anybody explain A3 b iv)
Can anybody explain A3 b iv)
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Biology; Chemistry; Physics: Post your doubts here!
- Thread starter scouserlfc
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I need to focus on Organic pretty badly, that's the only part where i am losing marks 
Yes it is ..
proof from 12 syllabus:
Aluminum is the most abundant metal to be found in the earth's crust. However, it is uneconomical to extract it from most rocks and clays, and instead, it is extracted from an ore called bauxite.
The ore is usually found near the surface in layers between 4 and 12 metres thick. It is mined by open-cast mining, which is relatively cheap.
Most bauxite ores contain between 25-30% aluminum oxide with impurities of sand and iron oxide. The impurities make the ore reddish-brown in colour. The two largest producers of bauxite are Australia and Jamaica. Once mined, it is then purified by dissolving it in sodium hydroxide. the impurities do not dissolve and are filtered off. The dissolved aluminium oxide is then precipitated out as aluminum hydroxide by diluting with water. This is then heated to form pure white aluminum oxide, or alumina. The aluminium is then extracted by electrolysis.
To conduct electricity, the aluminum oxide must be molten. However, it has a high melting point (Over 2000C), so another aluminum compound called cryolite (Na3AlF6) is added. This lowers the melting point. During electrolysis, the aluminum ions migrate towards the graphite cathode, where molten aluminum collects and is siphoned out.
Cathode : Al3+(l) + 3e- ---> Al(l)
Anode: 2O2-(l) -----> O2(g) + 4e-
It requires 15 kilowatt-hours of electricity to produce 1 kilogram of aluminum.
heyy guys for chem is aluminium extraction (all with the cryolite stuff) is it included in the syllabus for 2012? if yes then plz give me some notes on it if u have any thanks
Yes it is ..
proof from 12 syllabus:
Aluminum is the most abundant metal to be found in the earth's crust. However, it is uneconomical to extract it from most rocks and clays, and instead, it is extracted from an ore called bauxite.
The ore is usually found near the surface in layers between 4 and 12 metres thick. It is mined by open-cast mining, which is relatively cheap.
Most bauxite ores contain between 25-30% aluminum oxide with impurities of sand and iron oxide. The impurities make the ore reddish-brown in colour. The two largest producers of bauxite are Australia and Jamaica. Once mined, it is then purified by dissolving it in sodium hydroxide. the impurities do not dissolve and are filtered off. The dissolved aluminium oxide is then precipitated out as aluminum hydroxide by diluting with water. This is then heated to form pure white aluminum oxide, or alumina. The aluminium is then extracted by electrolysis.
To conduct electricity, the aluminum oxide must be molten. However, it has a high melting point (Over 2000C), so another aluminum compound called cryolite (Na3AlF6) is added. This lowers the melting point. During electrolysis, the aluminum ions migrate towards the graphite cathode, where molten aluminum collects and is siphoned out.
Cathode : Al3+(l) + 3e- ---> Al(l)
Anode: 2O2-(l) -----> O2(g) + 4e-
It requires 15 kilowatt-hours of electricity to produce 1 kilogram of aluminum.
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what about it ? you just need to type the definition.
Reduction: The removal of oxygen, the gain of hydrogenm, the addition of electrons or a decrease in oxidation state.
No i said question 3 part b iv)
The mass of uranium one ?
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my mass is coming 881,310 grams (0.881 Tonnes) .. is it even close to the right answer?
Was a really tough question ! needed some thinking
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compared to aluminium iron is a less reactive metal only those metals can be extracted from electrolysis who are high in the reactivity series and iron is extracted from its ore using carbon as a reducing agent
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Iron can be reduced by heating with carbon which is a lot cheaper than doing an electrolysis of Iron that's the reason why iron is not extracted using electrolysis, Since aluminum cannot be extracted by heating with carbon (carbon is below in the reactivity series) the only method to extract aluminum is Electrolysis.
The oxide of Aluminium is very stable therefore it can only be extracted by electrolysis,while iron which is lower in reactivity series is extracted with the help of a reducing agent-either carbon or hydrogen.
Help please ?
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I answered it above .. you didn't reply
my mass is coming 881,310 grams (0.881 Tonnes) .. is it even close to the right answer?
Was a really tough question ! needed some thinking
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what is your equation of step 2?
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UF4 + 2Mg ---> 2MgF2 + U.
0.881 is the answer !!
Hw did u get it ..??
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First get the number of moles for U02 .. Mr of U02= 270g .. 1 tonnes = 1million g
Moles of U02=1million/270 = 3703.
1 Mole of U02 produces 1 mole of U .. check the equations .. that's how i got it.
therefore 3703 produces 3703.
Mass of U= Moles*Mr
= 3703*238
= 881,481 grams (divide it by 1 million to get the answer in tonnes)
thats correct,approximately.
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Thankss A Loaddd guys syed1995 and rabiafarooq101 !!
i wish i cud hit the like a thousand times! thats a load off! ^__^
i wish i cud hit the like a thousand times! thats a load off! ^__^
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U have the equation of step 1 it shows that 1 mol of UO2 gives 1 mole of UF4 so calculate the mass of 1 mol of U02 mr is 270 multiply it with 1 so 1 mole is 270 g now notice in step 2 1 mole of UF4 gives 1 mol of uranium that means 270g of UO2 gives 238g of uranium now 1 tonne has 1milliong calculate the number of moles of 1 tonne of UO2 they come 3704 as ratio is 1:1 calculate the mass of 3704 of u it comes as 881552g now divide this by 1 million ans is 0.88