question (1 Viewer)

[richz]

hello

I need help for this question

Compostition of Bauxite

Constituent Compostition(%)
Al203.3H2O 64.8
Al2O3.H2O 13.7
Kaolinite (clay) 8.6
Quartz (SiO2) 0.9
Haematite 8.6
TiO2 2.8

The first step in the process purifies the ore prior to reducing it to the metal. At the conclusion of the refiniing process all of the al has been convereted to anhydrous al oxide (Al2O3).

q: How many moles of Al2O3 would be produced from a 500kg sample of bauxite?

The electrolysis of Al2O3 is a complex process. Oxygen produced at the anode combines with the carbon anode to produce carbon dioxide.

Q: if each mole of al requires 1.8MJ of energy. How much energy is needed to extract all of the al from the 500kg sample??

also would these qs be asked in the hsc anymore??

 

[currysauce]

Do they give you a chemical formula for Bauxite?

 

[velox]

yes im pretty sure they do because i have had a similar question in an exam last yr

 

[richz]

nope isnt bauxite aluminium oxide . water. But i dunno how many waters

 

[Dreamerish*~]

also would these qs be asked in the hsc anymore??

DEAR GOD i hope not

EDIT: is the answer to the first question around 270g?

 

[currysauce]

If i had an equation, i could do this.... but i don't know the bauxite formula

 

[Dreamerish*~]

would you have to?
i mean, it said that you have 500g of bauxite right?

Constituent Compostition(%)
Al203.3H2O 64.8
Al2O3.H2O 13.7

therefore you have:
0.648 x 500 = 324g of Al₂O₃.3H₂O and
0.137 x 500 = 68.5g of Al₂O₃.H₂O

so now i'm assuming that by dehydration:
Al₂O₃.3H₂O --> Al₂O₃ + 3H₂O
there are 324g, i.e. 2.08 mol of Al₂O₃.3H₂O therefore 2.08 mol of Al₂O₃ is produced: 212.16g

with the same calculations, Al₂O₃.H₂O dehydrates to produce 58.22g of Al₂O₃

adding them two together we get 270.38g

i really don't know if it's right i've never seen anything like it.

 

[thunderdax]

er, it actually says 500kg, and the question is how many moles...
I don't have a calculator with me, but with the second question, don't you just multiply this number of moles by 2, and then multiply by 1.6.
Man I'm lazy

 

[Dreamerish*~]

this is why i should practise reading questions properly.

well i get 2.65 moles from my answer but it's on 500g

 

[richz]

ok guys the answer for the first part is 2649 moles. Its not really clear, there maybe a decimal pt somewhere im not sure, but i dont understand how the answer was obtained. fro the 2nd part the answer is 9536 MJ. Again there is no working

 

[richz]

this is why i should practise reading questions properly.

well i get 2.65 moles from my answer but it's on 500g

i think thats rite if its 500kg, thnx i'll have a look at ur working now

 

[currysauce]

i wouldn't be worried if you can't do this question, not only have i never seen this type of question, your not given working, so stuff it

 

[richz]

o ok kool, it was from an 02 school paper anyway.