I think I got 15 B, and 1.78% nitrogen, 0.9 grams for the ethanol combustion, anyone else?
Ethanol mass was around 3.58g or something like that...i got 15 B but i dont know why, 1.8% nitrogen because it was 2s.f. i think... and if not i got like 1.77%.
your ethanol is incorrect though, sorry dude
does anyone have a copy of the multiple choice questions? I left mine in the exam room
also, did people get for the galvanic cell one that Fe3+ reduced to Fe2+? and that bloody shipwrecks question on silver plating the nickel spoon. I had the spoon the cathode and a graphite anode in a silver nitrate solution. But would it work seeing the water has a higher electrode potential?
I made the spoon the cathode in an AgNO3 solution, with an inert platinum anode. Silver deposited on cathode, voila - silver plating!that bloody shipwrecks question on silver plating the nickel spoon. I had the spoon the cathode and a graphite anode in a silver nitrate solution. But would it work seeing the water has a higher electrode potential?
im the same. NOBODY WILL POST IT UP.does anyone have a copy of the multiple choice questions? I left mine in the exam room
also, did people get for the galvanic cell one that Fe3+ reduced to Fe2+? and that bloody shipwrecks question on silver plating the nickel spoon. I had the spoon the cathode and a graphite anode in a silver nitrate solution. But would it work seeing the water has a higher electrode potential?
yep 0.9g for ethanol
i think ppl have calculated it wrong coz they got answers like 550g i was like wtfffffffffffffffffffffffff..lol
+1i don't know how you did it...
but,
/\H = -mc/\t
where m was 210, c is 4.18, t was 65
/\H = 57.057 KJ/g
turn this into /mol
57.057 x mm(ethanol) / m(ethanol) = 1376/2 (50% heat lost to environment)
rearrange to find m(ethanol)
m(ethanol) = 2624.622/688
=3.8 grams (2 sf)
Hey do you guys see any problems with my MC answers?
1. C
2. C
3. D
4. C
5. A
6. D
7. B
8. A
9. C
10. B
11. D
12. A
13. B
14. B
15. A
I got 1.77% for the nitrogen content, 3.8 something grams for the ethanol and 0.9 V for the galvanic cell
you should never ever round.If i got 1.78% because i rounded off the number of moles in the previous question do i still get full marks?
no, you're not meant to round until you get to your final answer, where you put it in the correct amount of sig figs.He guys with the Nitro calc I got 1.45% only because I rounded off everything, I showed all working do i still get the full mark I was ccnsistant 3dp for every thing
perhaps, as it said 50% is lost to the environment.decapitated said:I swear they said heat of combustion was 1367 kj/mol. I have to get my eyes checked- ended up with 4.1g
I thought that it could've been worser, seriously. I was shitting myself before the exam and found that the questions were all answerable and I'm glad that its over and my 2 days cramming should pay off. I reckon that I'll get somewhere between High 70's low 80's.
As for that NH3 question, I forgot to convert it into percentage >< But yeah, I got around 2.2%
Couldn't do Q14 for Multiple choice, so just guessed that >_<
Also, the one with the titration graphs was alright, I put CH3COO- for the conjugate base, although now thinking about it, that's probably one.
And for whoever it was who wanted to know, I put NH3 + HCl --> NH4Cl for the bread question.
pretty sure thats right, prob 95%ishI got: 1.78% nitrogen, 3.51g for ethanol and 0.9V for the cell.
I thought it was different to past exams. A bit tricky in places but overall ok I guess. We can only wait and see I suppose.