Exam Suggested Solutions

[Aba]

Meh, believe what you want uhm, 'Aba's Friend', we'll see who was right when we see the statement of results.
Honestly, your calculations make no sense >.< What Sally said was right, they would be trying to test who actually knows when to do what, as opposed to someone who just plugs in formulas.

lolllll, he may be starting to admit defeat, we will have to wait and see,

[sally_hates_school]

Meh, believe what you want uhm, 'Aba's Friend', we'll see who was right when we see the statement of results.
Honestly, your calculations make no sense >.< What Sally said was right, they would be trying to test who actually knows when to do what, as opposed to someone who just plugs in formulas.

lolllll, he may be starting to admit defeat, we will have to wait and see,

theres a difference between admitting defeat and being bored with your opponents... intelligence.......... im just saying

[bilgia]

guys just go to sleep now exams are over

[jeremykleeman]

So what's the verdict on the 45 peak in ethanol spectrum? Is Mao correct in saying loss of hydrogen from hydroxyl group? (that's what I said). My friend suggested it was loss of any hydrogen atom in the ethanol, which explains the high abundance? What's our verdict?

[shinny]

I'm....pretty sure Mao is right. The calculations make sense and thats exactly what I did and what i got =P but yes, leave the keyboard fighting for when the statement of marks comes. and about the hydrogen atom...does it matter? its H+ either way =p

[sally_hates_school]

guys just go to sleep now exams are over

this might be like a bit, idk personal or whatever lol, but can i ask what mark you got on your chem exams? i just wanna know because i'd love to get a 36 in chem , i need 35 for the course i wanna do :p

[jeremykleeman]

I'm surprised we aren't all complaining about the time of the exam. Seriously... it was lunch time at my school and the kids where making a lot of noise outside! Not to mention hunger and fatigue factors. Exams should never go over lunch time... Can't wait for the GAT tomorrow...

[bucket]

Dude!
The double dilution was irrelevant!!!
I'm positive about this!
They would DEFFINITELY test people on recognising what information is relevant to what you are trying to find!

If you have 0.5mol of something in a 10mL solution, and you dilute it to 100mL, the mol doesn't change! Therefore the dilution is irrelevant!

I originally did the question using concentration and I just checked it again using moles, and I still get the same answer (Mao's answer).
The gist of the question was:
MnO4 ------> made up to 1L -------> 25mL aliquot taken --------> diluted to 100mL
therefore iii)
c(MnO4) = 35mg/L in the 100mL
c(MnO4) = 0.035g/L in the 100mL
c(MnO4) = 0.035/(16x4+54.94) mol/L in the 100mL
n(MnO4) = above c x 0.100
n(MnO4) = 2.94 x 10^(-5) mol in 100mL
n in 25mL = n in 100mL (simply diluted: mole doesn't change, concentration does)
n(MnO4) = 2.94 x 10^(-5) mol in 25 mL
n(MnO4) = 2.94 x 10^(-5) x 1000/25 mol in 1L
n(MnO4) = 0.001177 mol in 1L
etc.. which gives you 64.67mg
So Mao i right

exactly!
thats what I did! perfect!

[sally_hates_school]

Dude!
The double dilution was irrelevant!!!
I'm positive about this!
They would DEFFINITELY test people on recognising what information is relevant to what you are trying to find!

If you have 0.5mol of something in a 10mL solution, and you dilute it to 100mL, the mol doesn't change! Therefore the dilution is irrelevant!

I originally did the question using concentration and I just checked it again using moles, and I still get the same answer (Mao's answer).
The gist of the question was:
MnO4 ------> made up to 1L -------> 25mL aliquot taken --------> diluted to 100mL
therefore iii)
c(MnO4) = 35mg/L in the 100mL
c(MnO4) = 0.035g/L in the 100mL
c(MnO4) = 0.035/(16x4+54.94) mol/L in the 100mL
n(MnO4) = above c x 0.100
n(MnO4) = 2.94 x 10^(-5) mol in 100mL
n in 25mL = n in 100mL (simply diluted: mole doesn't change, concentration does)
n(MnO4) = 2.94 x 10^(-5) mol in 25 mL
n(MnO4) = 2.94 x 10^(-5) x 1000/25 mol in 1L
n(MnO4) = 0.001177 mol in 1L
etc.. which gives you 64.67mg
So Mao i right

exactly!
thats what I did! perfect!

me too

[jeremykleeman]

I did that too, except i think i gave only 3 sig figs.

Actually maybe only 2...

[bucket]

Sig figures is my weak point and I think I put three aswell, but;
"the absorbance, at 525 nm, of this solution was 0.70"
that 0.70 is two sig figures O_O.

[shinny]

vcaa allows one sig fig either way (so 2, 3, or 4 sig figs if its meant to be 3 is still full marks)...its in the examiners reports. so its pretty hard to lose the mark for it =T

[werdna]

what was the exact qn for 8 in mcq?

[werdna]

and i stuffed up molecule Y.
I put circled and named 1-butanol
Do i get consequential for naming it right?

[shinny]

Q8 asked what biomolecule would have carbon, hydrogen, oxygen, nitrogen and phosphorus in it..or something along those lines