Howd you go on the chem exam?

[stonecold]

ok for the benxoic question i forgot to double the the delta H...
in the calculations i used the undoubled number... is that wrong??

no.

[happycat]

Was I supposed to say that mass of lithium was 80.3 or just 80 I went by least number of sig figs that was for litium in data sheet? Will I be penalised for not having correct number of sig figs?

[mirra250]

2C6H5COOH + 13O2 -> 12CO2 + 6H2O delta(H) = -6454

wrong. you have 14 C on the left, 12 on the right.
The real equation is
2C6H5COOH + 15O2 -> 14CO2 + 6H2O delta(H) = -6454

[stonecold]

Was I supposed to say that mass of lithium was 80.3 or just 80 I went by least number of sig figs that was for litium in data sheet? Will I be penalised for not having correct number of sig figs?

I also put 80g.  According to the exam report in 2008, you take into account sig figs of molar masses.

[andy456]

ok for the benxoic question i forgot to double the the delta H...
in the calculations i used the undoubled number... is that wrong??

no.

So i had to multiply the n(benzoic) by 3227

[kenhung123]

Yea, you use 2 for that.

[happycat]

Was I supposed to say that mass of lithium was 80.3 or just 80 I went by least number of sig figs that was for litium in data sheet? Will I be penalised for not having correct number of sig figs?

I also put 80g.  According to the exam report in 2008, you take into account sig figs of molar masses.

Well thanx you

[98.40_for_sure]

You didn't have to double the Oxygens in that balancing did ya? i think i left it as 7.5

[kenhung123]

ok for the benxoic question i forgot to double the the delta H...
in the calculations i used the undoubled number... is that wrong??

no.

So i had to multiply the n(benzoic) by 3227

Yea, however if you did ratios, you would have made 2 moles benzoic =double heat of combustion

[darkphoenix]

You didn't have to double the Oxygens in that balancing did ya? i think i left it as 7.5

Yeah same here. I think you can do either, i remember in assessment reports in previous years they accepted both.

[8039]

What did people get for the balanced complete combustion of benzoic acid???

I got 2 mol

[monicapham93]

oh im feeling much better reading these answers
ALTHOUGH i stupidly got that replace E values wrong

i thought i worked it out to be Cd = +.22V
but i was completely off track

[garliczombie]

It wasnt bad. I did shit on it though because i gave up on chem after my mid year score of a B. just bludged the whole semester. SCHOOLS FINALLY OVER THOUGH!!!!!!!!

[Stroodle]

Was I supposed to say that mass of lithium was 80.3 or just 80 I went by least number of sig figs that was for litium in data sheet? Will I be penalised for not having correct number of sig figs?

I also put 80g.  According to the exam report in 2008, you take into account sig figs of molar masses.

Man that's annoying. In The Age, before the mid year, there was an article where the chief examiner said that molar mass sig figs shouldn't affect your answer's sig figs. So ever since then I've gone by this..

[crunch 29]

what was the correct E naught value ?
AgCl.... = +0.22V ?