Trial exams discussion

[methodsboy]

Cool, i understand now. Thanks every1 

[bloodboy]

its truee lol

[kendraaaaa]

Just did STAV '09. Was pretty easy, got 73%. Really want to be averaging 85%+ 

Oh well, could someone please help me with this question. Part d)
(answer attached)



Thank you

[chem-nerd]

the H⁺ is from the lactic acid and the HCO₃^- is is from the sodium hydrogen carbonate (NaHCO₃) (a base), hence it is a neutralisation reaction.

[kendraaaaa]

God I'm dumb, haha that's easy. Thanks

[bloodboy]

73% is easy? :S

[kendraaaaa]

Difficulty is subjective

[kendraaaaa]

How would I go about doing this question, without having memorized the half equations for the fuel cell.

(from STAV '09)

Q13. In an oxygen/methanol fuel cell:

A. the oxidant is methanol and it is oxidized at the anode
B. the oxidant is methanol and it is reduced at the cathode
C. the redctant is methanol and it is oxidised at the anode
D. the reductant is methanol and it is reduced at the cathode

[bem9]

u can rule out A and D since an oxidant is not oxidised, it is reduced and a reductant is not reduced, it is oxidised.

also im pretty sure methanol has go to carbon dioxide and water (what else could it do?) so the oxidation number increases from -2 to +4, it is oxidised and is the reductant

therefore C

[NE2000]

Yep essentially for that question you don't need to know anything about fuel cells. Firstly you know: oxidation occurs at the anode. B and D are out. Secondly you know that the reductant is oxidized. Therefore C. You can ignore the rest of the question.

[ross huggard]

Will the end of year exam be as tough as the mid year? I presume they would write the two exams prior to the start of the school year, so they couldn't adjust it..?
The unit 4 area of studies are probably easier than unite 3 anyway i guess

[methodsboy]

^it should be easier since that unit 3 one was a killer

[ross huggard]

^it should be easier since that uni t4 one was a killer

Unite 3 do you mean..?

[ross huggard]

or unit

[jaja]

hey just did chemology 2008 exam.....
) Question 3 (8 marks)
A typical Hall-Heroult cell used for the electrolytic extraction of aluminium from alumina, Al2O3,
operates at 5.00 volts with a current of 150 000 amperes.
(a) Write the half equation for the reduction of the aluminium ion in the alumina.

wouldn't the product be Al (s) but the answer says Al (l)