Unit 3 Chemistry 2010 exam review
By Heath McGregor on Jun 9, 2010 in VCE Chemistry, VCE Exams
Hi all,
So you’ve completed the Unit 3 VCE Chemistry exam for 2010. What did you think of the paper? What was hard? What was easy? How do you think you went?
Let us know your thoughts and comments below (please keep them clean!)…cheers
(7 votes, average: 3.57 out of 5)
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Tom | Jun 9, 2010 | Reply
Short and easy.
Ben | Jun 9, 2010 | Reply
It was heaps easier than the exams from the past few years!
Quite long.
Heaps of easy questions on organic chem
Chem analysis was a little more challenging; still fairly easy though
Anna | Jun 9, 2010 | Reply
Did you guys get propanal for the HNMR Ir and CNMR question? Google it if you don’t know the structure.
Phill | Jun 9, 2010 | Reply
Wow…. I can’t believe how challenging that exam was… Multi’s are all right, for revision I did random Q’s from the book… But as for everything else.. death… Love bio chemistry, hate chemical analysis… questions like that, we only did 2 chapters on!!! its hardly proportioned right
Ray | Jun 9, 2010 | Reply
was it 6 double bonds or 3 double bonds?
and was it 49 peptide bonds or 50?????????????????????????????????? :S
Brendan | Jun 9, 2010 | Reply
found it fairly easy, however comparing with everyone else afterwards, im pretty sure i made heaps of silly mistakes, and had vastly different answers to everyone else
miki | Jun 9, 2010 | Reply
It was alright, so glad i did the 2009 one — helped a lot. I probably did better 2009 then this one though.
I say it’d be marked down a lot though, considering it was pretty easy.
Raygay | Jun 9, 2010 | Reply
erm………..for the first qusetion in section B…. was the answer in 3 sig figures or 4?
i got 2.82% is that righttttttttttttttt
anon | Jun 9, 2010 | Reply
i got 3 sig figs but got around 3% i think..
miki | Jun 9, 2010 | Reply
same aroun 3% (i dont remember) but i did two sig figures
Bay | Jun 9, 2010 | Reply
was it 6 or 3 c=c bonds???
also was it 49 or 50 peptide bonds????
tina_tin | Jun 9, 2010 | Reply
yeah, i found the chem exam okayy, and i did 2.82% as well (3 sig figs)
what did everyone get for the mmol glucose something question, i got something like 0.0802
greg stump | Jun 9, 2010 | Reply
the exam was okayy, especially the mutiple choice, but i couldnt really do that glucose question
Paul | Jun 9, 2010 | Reply
Easy for sure..
It was 3 sig figs.. but i got 3.81% i think.
for the mmol glucose i got around 30mmol = 0.03mol, which was 5.4g
anyone else get that?
Paul | Jun 9, 2010 | Reply
OH ps. for the question where we had to figure out the molecule with the infrare, H NMR and C NMR graphs – what was the molecular formula? Was it C3H6O2???
If so, did everyone get ethyl methanoate?
nick | Jun 9, 2010 | Reply
multiple choice 15… the insulin one,i got 49 because the 51 amino acids were split over 2 chains?
and SB 2di) about the equivalent nuclei… most ppl at my school got 2 but i got zero because the protons on the adjacent carbon werent equivalent, ie. in the same chemical environment?
Paul | Jun 9, 2010 | Reply
nick – i got the same, 49 links
hmm with SA 2d)i)… i got 2.. i see what you mean by ‘equivalent’ – i was wondering myself why they had ‘equivalent’ – so you could be right
nick | Jun 9, 2010 | Reply
yea i got 3.82% did u round off?
for the mmol i got 5.40grams 3sig figs
Daniel | Jun 9, 2010 | Reply
I got 5.4 g aswell, so glad someone else did…
I also got 49, but if a peak is split into 3, there has to be 2 protons on the neighbouring carbon.
What did people draw as their proposed structure?
Tee | Jun 9, 2010 | Reply
How do you people remember these details?!
I only remember the how many double bonds question.
Steph. | Jun 9, 2010 | Reply
much more straight forward than previous years. i still had trouble with some of the short answer questions.
what did you’s put for the last multiple choice question with the big polymer chain?
did you get 6 double bonds for the polysaturated fat?
Tom | Jun 9, 2010 | Reply
I also got 3.81% may have lost a mark for sig figs though.
Tom | Jun 9, 2010 | Reply
Paul. I got 54KG, so chances are you are correct, and I messed up my decimal point.
Nutsack | Jun 9, 2010 | Reply
Insulin question was 49.
Glucose was 5.4g
Iron I’m pretty sure was 3.82% (3sf)
Got ethyl methanoate for one of the questions
and I don’t think the rule “equivalent H’s don’t split each other” is applied for VCAA exams
Craig | Jun 9, 2010 | Reply
Not happy with performance at all. I thought it was average while everyone thought it was easy…
jane | Jun 9, 2010 | Reply
Found it okay.
Screwed up the last question for some crazy reason – I’d done the exact question at least 3 times.
Couldn’t work out the mmol question.
I got 49 for multi choice as well.
What did people get for the product that couldn’t form from the reaction? Was it B?
jane | Jun 9, 2010 | Reply
And also, was the instrumentation analysis question an ester?
Dylan | Jun 9, 2010 | Reply
paul thank god i go the exact same thing aws you!! i persoanlyl thought it was definetly a tad to easy! but accidently stuffed up on the stupid structure of the compund from NMR, etc!
Defiently much to easy though! complete role reversal this year for chem and bio! they were much much to nice!
did anyone get 6 double bonds for the cervaic acid question!!
ell | Jun 9, 2010 | Reply
I got B as well, 5 mol of oxygen or something, I hope it’s right :S I kinda screwed up on the multiple choice, went through it too fast
jane | Jun 9, 2010 | Reply
Yep, 6 double bonds.
Meaning the formula was C21H33COOH?
Jake | Jun 9, 2010 | Reply
I found it really easy. Probably lost 1-2 silly mistakes! Woohoo!!!!!!!!!
feelin’ good!
michael | Jun 9, 2010 | Reply
I got 50. Shouldn’t it be 50?
Nutsack | Jun 9, 2010 | Reply
One too many H’s I think Jane :S I thought the Mm was 328? I dunno, can’t really remember.
Sammy | Jun 9, 2010 | Reply
LOL, pretty easy! I have a feeling the A+ cut offs are going to be VERY high this year! Finished with 5 mins to spare, lol. Too easy!
Sasha | Jun 9, 2010 | Reply
OMG! SO EASY!!!
Closed my eyes rubbed them, opened them again.. couldn’t believe I finished with 10 mins to spare.
Lisa | Jun 9, 2010 | Reply
I GOT 6 BONDS
is it 6 bonds or 3 bonds?
omg everyone is saying different things so i’m confused.
and as for the glucose question…would i be marked incorrect if i wrote 5.40g instead of 5.4g?
Lisa | Jun 9, 2010 | Reply
did anyone get 0.91 L?
John | Jun 9, 2010 | Reply
Can’t be five mole in excess, there was only one mole of each
affffff | Jun 9, 2010 | Reply
did anyone get 2/7 moles in excess
yvi | Jun 9, 2010 | Reply
did anyone else get like 1.14L for the volume of a question where density was given? I’m not sure if i did it correctly!
The exam seemed really easy at first, but on second thoughts….I think there were some qns I got tripped up on!
Emily | Jun 9, 2010 | Reply
I found it okay but I made at least 2 stupid mistakes; the structure one, and one of the multi choice about the amino acid chain. I read it as 50 amino acids instead of 51 so I said it had 48 peptide links damn it!
Tee | Jun 9, 2010 | Reply
somehow i got 7 double bonds
first i did it math way with two equations for x(no. of H missing)
then i did it by taking masses away M, i’m almost convinced 7 double bonds is wrong though.
Dave | Jun 9, 2010 | Reply
0.73L here, two significant figures because of the density at 0.79g/mL?
Jacinta | Jun 9, 2010 | Reply
For the concordant titres..
did everyone plus every single one
I only chose the last two…..
Jake | Jun 9, 2010 | Reply
Someone please answer my questions:
1. Did anyone get 0.91L ?
2. Is it okay to write 5.40g instead of 5.4g?
3. Were the monomers propene and but-1-ene?
Paul | Jun 9, 2010 | Reply
jacinta – i only did the last two as well! I have no idea if we were meant to though?
Also, with the 3.81/3.82% i think i got 3.81 because when i rounded for previous questions, i used the rounded answer, not full answer. i’m sure they’ll give marks for both!
Cervaic acid was definitely 6 double bonds.
Dave/yvi i got 1.5L… and yeah it was 2 sig figs cause of the density being two.
yvi | Jun 9, 2010 | Reply
I got propene & but-2-ene but not sure if that’s right.
Paul | Jun 9, 2010 | Reply
Jake – i’m not 100% sure if you lose a mark for sig figs even if it’s not stressed in the question. I would like to know myself if anyone else can answer
And no… i believe monomers were propene and but-2-ene (answer B)
Emily | Jun 9, 2010 | Reply
did anyone get 1.5L for the methanol question?
Anna | Jun 9, 2010 | Reply
I was under the impression that you could have + or – one for sig figs? I got 5.4g as well but I got something called propanal for the last one (i looked it up.) anyone else get that??
Paul | Jun 9, 2010 | Reply
sorry anna – you got propanal for which question?
johnny | Jun 9, 2010 | Reply
i think it was 7 double bonds, because there are 6 C=C bonds and 1 C=O bond, so 7 in total. They didn’t specify in the question the type of double bond.
Dave | Jun 9, 2010 | Reply
I got propene and but-2-ene and i looked up that fatty acid, six double bonds.
Dave | Jun 9, 2010 | Reply
damn, six carbon bonds i mean, seven in total
kevin | Jun 9, 2010 | Reply
this is what i got.
average titre was 22.00ml, 3.81 percent for percentage mass of iron ions.
-6 double bonds for the polyunsaturated thing. C22H32O2 was the formula or C21H31COOH
-5.4g of glucose.
-ethyl methanoate for the hydrocarbon that doesnt react with a base (cannot be carboxylic)- 3 carbon and 3 hydrogen environments. the ir was corresponding to a c-o double bond.
-spectrum A was not the nitrogen dioxide.
peak @ 30 corresponded to a NO+
-Fractional distillation- a bunsen burner did not provide enough heat.
3/1 ratio of the triglyceride vs ethanol- the next question was basic stoich. forgot my answer thou.
cannot remember anything else.
Paul | Jun 9, 2010 | Reply
That’s interesting! I cant remember if they specified ‘carbon to carbon double bonds’.. let’s hope they accept both!
johnny | Jun 9, 2010 | Reply
Yes, there are 6 bonds in the C21H31- part, but there is also one more double bond in the COOH, so 7 in total
Paul | Jun 9, 2010 | Reply
Kevin – i got the same answers besides the titre, i only took the average of the last two
and also – with the bunser burner.. i said it provided too MUCH heat too quickly – and it would be difficult to evaporate out only one substance at once because the bunsen burner cant keep a constant temp (at say 97.2 degree for example)… did anyone else get my answer? lol
Ace | Jun 9, 2010 | Reply
it was actually relatively easy. But simple calculation errors screwed me up.
It was 7 bonds in total
with the iron question, i had done everything right, but like the idiot i am, i put an extra decimal place after the iron.
SO percenage was 0.381
i will still get marks for the process thoguh right? cuz the process was right
Ace | Jun 9, 2010 | Reply
did everyone get 0.135 or something for the third multiple choice,
finding the mass of Cl atoms in the molecule with the carbon mass
Ben | Jun 9, 2010 | Reply
I had 5/7 moles in excess – 2/7 moles reacted.
Had half hour to spare :S
Ace | Jun 9, 2010 | Reply
definitely around 90 percent in terms of a raw percentage. hopefully.
Paul | Jun 9, 2010 | Reply
Ace yeah Q3 answer was A
man im so cut about that double bond question!!!! :’( does anyone have the exam so i can read the exact question?
Ace | Jun 9, 2010 | Reply
ye i wrote 6 double bonds, not 7 zzzz
misread the question..
kevin | Jun 9, 2010 | Reply
average titre is taken from 3 concordant titres. so yeah. i took the average of 3 volumes. it was 21.9967? but 22.00 for significant figures.
5/7 moles was in excess.
i dnt care anymore. nothing i can do to change my score.
but does anyone know when we get our results back?
johnno | Jun 9, 2010 | Reply
it was quite good
better than 2009
Pat | Jun 9, 2010 | Reply
Yes, i got 1.5L to 2 sig figures
Pat | Jun 9, 2010 | Reply
and it was definitely 6 double bonds
steve | Jun 9, 2010 | Reply
So far looks like I got all the calc questions right, but I’m kinda worried about all those explanation questions. Like with the alcohol chromatography, what were we supposed to say??
crystal | Jun 9, 2010 | Reply
our teacher was fired last month as he didnt teach us the course proparly. so we had one month to learn the course.
everyone including myself found it really easy.
so im scared.
itll be really hard to do well on this exam in terms of comparative marking
Pat | Jun 9, 2010 | Reply
i thought the question was only asking for carbon-carbon double bonds along the chain, do u really think they’ll take the C=O into it?
Pat | Jun 9, 2010 | Reply
my structure looked like this;CH3-CH2-O-C(H)=O
so the splitting and the IR spectrum still all matched, and it cannot react with a base because it no longer has the COOH group.
Paul | Jun 9, 2010 | Reply
Damn i got the titre thing wrong too ;’(
Also this may seem like a stupid question; but the conversion of salicylic alcohol into salicylic acid question:
i) What type of reaction is it?
I said oxidation.. was it meant to be Redox?
lisa | Jun 9, 2010 | Reply
er..for the ratio thing i wrote :
3:1 so 3
is that right..
johnno | Jun 9, 2010 | Reply
what do you think will be required to get an A+
90%???
abe | Jun 9, 2010 | Reply
2008 was 88%-although the trial exam was very similiar and would have lifted up makrs
2007 was 78%
so i reckon around 90%
jake | Jun 9, 2010 | Reply
yep agree with pat they were only asking for C=C bonds
Dave | Jun 9, 2010 | Reply
Structure is HCOOCH2CH3 i think
Justin | Jun 9, 2010 | Reply
I think it’d be really harsh of them to take into account the C=O bond, but it probably be the sort of thing they’d do =S I got 1.5L too…there seems to be a fairly even split between 1.5 and 1.4 though
yvi | Jun 9, 2010 | Reply
for q 1
I took the last 2 titres in calculating the average! I thought the others didn’t give concordant values??
Paul | Jun 9, 2010 | Reply
Definitely HCOOCH2CH3.
If you guys want to see the exam paper you can download here http://www.mediafire.com/?mwzmmtz2yty#2
It says (for the double bond question):
“The number of carbon-carbon double bonds in a molecule of cervonic acid can be determined by titration with iodine…”
then it says “i) Calculate the number of double bonds in a molecule of cervonic acid.”
That is really misleading if they are asking for the C=O too
Dylan | Jun 9, 2010 | Reply
In every question i have ever done concerning double bonds, and even in check points im pretty sure they never specfied carbon to carbon double bonds, im sure it is definetly 6. Apparently my chem teacher said that is students only wrote Cr2O7 -2/H+ but didnt write the actual name of the catalyst (acidified dichromate) for the oxidation reaction than you did get the mark as it said to specifically name! Im pretty sure the cut off rate will be simialar to 08, i know i found it easy but a lot of people i have talked to made stupid mistakes and a lot have said it was hard
ying | Jun 9, 2010 | Reply
what is the answer for Q9 short answer?
was it either methanol or ethanol?
or was it either butanol or pentanol?
Justin | Jun 9, 2010 | Reply
actually it says to “name” ethanoic acid/anhydride, it only says to “suggest” the catalyst, so its possible that the formula would be accepted
abe | Jun 9, 2010 | Reply
what did you guys do as the reason a bunsen burner couldn’t be used?
Paul | Jun 9, 2010 | Reply
ying – i believe it is methanol/ethanol, because if they were in the mixture, they would have vapourised before 92.7, and it says at 92.7 the FIRST substance is collected or whatever.. therefore neither of meth/eth can be in the mixture
Nutsack | Jun 9, 2010 | Reply
Bunsen burner not suitable as pure alcohols are flammable. Thought that was obvious?
Matt | Jun 9, 2010 | Reply
It was okay, I don’t think it was easy, but finished with about 5 minutes to spare
although I made some silly mistakes
neonlights99 | Jun 9, 2010 | Reply
Hmm…I got 6 double bonds, and the molecular formula was C22H32O2 (checked internet before)
I got 3.82% for the percentage…
For the three concordant titres, the three that I used were 22.03, 21.97, and 21.99
I think you missed the 22.03 one?
For the Bunsen burner, I said it gets too hot too quickly. It can’t be true that the Bunsen burner isn’t hot enough because the hottest part of the burner’s flame is several hundred degrees celcius, while we only need to heat the mixture up to one hundred and something dregrees celcius.
Nutsack, in the fractionating tower, I believe the flame wouldn’t be applied directly to the mixture, would it?
n | Jun 9, 2010 | Reply
yes i wrote ethanol seeing as the first one that vapourised was at 90 something degrees and so that was the first substance collected therefore it was ethanol or methanol with a lower boiling point.
Rory | Jun 9, 2010 | Reply
Did anyone else get the formula of the cervonic acid to be C22H22O2, and if so, I thought the amount of C=C bonds would be 12.
gul | Jun 9, 2010 | Reply
1a-20.00 ml
1e-3.82%
2e-Ethyl methanoate
6- glucose 5.4 g
1.5L for ethanol
I think cervonic acid one should be 6 bonds but because of confusion VCAA would accept both of answers, 6 and 7.
For Bunsen burner, I said ‘I would decompose the mixture’?Not sure though
***** | Jun 10, 2010 | Reply
agreed craig, i didnt think it was super easer or super hard average, what percentage mark would you have to get for RAW 35?
***** | Jun 10, 2010 | Reply
and what were the answers for the DNA molecule?
were we allowed to circle more than on letter?
chanel | Jun 10, 2010 | Reply
kelly | Jun 10, 2010 | Reply
i circle 2 letters for the dna molecule, and i got 3 cocordant values too
yvi | Jun 10, 2010 | Reply
it’s ok, we still have unit 4!
Dylan | Jun 10, 2010 | Reply
im pretty sure it was butanol or propanol, my chem teach also said so, even if the temperature at the top of the flask was 92 C or watever, methanol or ethanol could of still been in the mixture, but only as a vapour, it would of yet to have had the abilty to condense sooo it could of still been in the mixture even though it didnt seperate
many people at my school got Butanol or Pentanol
Nutsack | Jun 10, 2010 | Reply
If you’re collecting fractions of alcohol really not a good idea to have a naked flame hanging around. Can’t think of any other reason a bunsen burner wouldn’t be suitable seeing as it would still get hot enough and I can’t see why it will cause decomposition but a heating mat won’t?
jay | Jun 10, 2010 | Reply
i wrote the structure methyl ethanoate. would that be acceptable aswell?
Neko | Jun 10, 2010 | Reply
That was an epic fail for me. I got a few questions right, but most of it wrong. It simply because I was so exhausted that I couldn’t actually concentrate on what the question was asking! Having read that the overall opinion is that it was easy- DDD: I’m done for on this one.
kat | Jun 10, 2010 | Reply
i wrote the same thing jay, i think it is possible?…i hope so
n | Jun 10, 2010 | Reply
i think most people are saying it was easy because it was easier than the year b4 but then again we shouldnt be too cocky, they could have made some questions sneeky and we thought it was easy wen it really wasnt.
an | Jun 10, 2010 | Reply
i wrote that a bunsen burner would not be suitable as the heat it applies is concentrated to one point on the flask (so maybe the substance coming out wouldnt be pure?). the heating mantle thing would spread heat equally around the flask
fred | Jun 10, 2010 | Reply
I wrote bunsen burner would not be accepatble as the method of heating would be too rapid and not controlled enough. Does that make sense???
I also got butanol/pentanol as with fractional distillation, the sample collected first at the bottom has the highest boiling point, there no substances with a higher boiling point (i.e. methanol/ethanol) could have been in the mixture, otherwise they could have been collected first.
st | Jun 10, 2010 | Reply
I said the same thing as u an for the bunsen burner. Also would it have been right to say the bunsen burner heats it too fast seeing as the boiling point of most alkanols is under 100C?
Oh and that question about the ideal wavelength to use for analysing the three dyes in multichoice was the answer 500nm? I said it was cause they had to not overlap but not sure if overlap makes a difference.
Also the suggest a reagent question I just wrote Cr2O7- and didnt mention the H+. would that lose a mark cause technically I think it said “a” reagent and H+ is a seperate reagent isnt it?
jimmy | Jun 10, 2010 | Reply
i got pentanol/butanol
Paul | Jun 10, 2010 | Reply
Dylan… with that alcohol question, it said the FIRST fraction was obtained at 92.7… if there was ethanol or methanol in there, there would have been a fraction earlier than 92.7. It is DEFINITELY methanol or ethanol that could NOT have been in the mixture
Prav | Jun 10, 2010 | Reply
for the bunsen burner question, the answer was that the heat of the flame could not be controlled. therefore it is not adequete for this experiment since a precise heat is required.
Lisa | Jun 10, 2010 | Reply
Omg i misinterpreted the question and thought the mixture they were referring to was the FRACTION COLLECTED, so i wrote butanol. but they shouldve been clearer with the question cos them mixture couldve meant the mixture of the fraction collected????
and what did everybody get for the Rf question? i thought the lowest dot was the one needed for the calculation, but my tutor said it was the highest dot????? i don’t understand.
and i said the ratio was 3:1 instead of writing 3/1… would i be penalised for that
i made so many stupid silly mistakes…. so depressing. i’m not expecting an A+ anymore
ying | Jun 11, 2010 | Reply
for the ratio question, the question asks for the VALUE, not the ratio. so it should be 3. not in ratio form…..
and for the reagent question, i think in order to get the mark, you need to say ACIDIFIED “reagent name”, otherwise you dont get the mark for it.
dylan..yeh i put pentanol for that question, and now im regretting to put tat one up…hope we can get consequential mark for the second part which explains our answer @@
oh god…..this exam is gonna let those hard working ppl get 50s , not necessarily the smart ones.
michelle | Jun 11, 2010 | Reply
“oh god…..this exam is gonna let those hard working ppl get 50s , not necessarily the smart ones.”
YING! Isn’t that exactly what exams are supposed to do? And this Chemistry exam has ALWAYS done that!
Obviously even if someone is “smart”, but don’t put the effort in, they don’t deserve to get 50′s! And it is completely reasonable that even if someone is not neccessarily “smart”, but work hard, they are fully entitled to get high marks! grrrrr please don’t generalise like that! I worked hard, I made silly mistakes, it doesn’t mean I’m not “smart” or didn’t work hard!
annarose | Jun 11, 2010 | Reply
=P
Paul | Jun 11, 2010 | Reply
Lisa, your tutor is wrong! You are correct
The rf value was like 0.27 (option A) – as the stationary phase was polar, that means the most polar substance would be most strongly adsorbed and thus have the lowest Rf value 
DAMMIT.. i forgot all about the acidified reagent… i just did Cr207^2-, not Cr2O7^2-/H^+
yvi | Jun 11, 2010 | Reply
sorry about the duplicate post…I tried from my sister’s e-mail cos I thought it didn’t work….don’t mean to sound so angry! =)
Lisa | Jun 11, 2010 | Reply
ah! thanks paul. ahhh i walked out of the exam room feeling all good, but now i realise ive made so many mistakes like not rounding up my answers to sigfigs
sucks cos ive been working SO hard for this one stupid exam, but its all gone now 
Dylan | Jun 11, 2010 | Reply
Paul im sorry but i even asked my chemistry teacher, the highest temperatures are at the bottom of a distillation flask/tower, hence butanol would of come out at temperatures higher which were lower on the flask! not methanol or ethanol as it has the lowest boiling points.
Sasha | Jun 11, 2010 | Reply
does anyone know where we can get copies of the paper? has it been uploaded somewhere?
and yeah i got 3.82% i think and 6 double bonds found it fairly easy but pretty sure i made some mistakes
Baker | Jun 11, 2010 | Reply
@ Sasha, was it 6 or 7 double bonds?
Can someone clarify this?
***** | Jun 12, 2010 | Reply
DID ANYONE GET 3.75%??
paul | Jun 12, 2010 | Reply
Dylan… hmm i’ll see what my teacher says on tuesday, but how can the top of the distillation flask be hotter than the base where the heat actually comes from?
paul | Jun 12, 2010 | Reply
OH WHOOPS I misread what you said.
I think what is going on here is a different interpretation of the question. Do you think that the ‘mixture’ is the liquid at the start? Or the liquid that is gained at the end?
yvi | Jun 12, 2010 | Reply
Overall the paper was less difficult than last year’s, but it was easier to make mistakes because VCAA had some sneaky questions. I made really dumb mistakes and I feel the same as you lisa…it IS depressing. Don’t worry! I don’t think doing many practice exams really helped me, cos it was different to what I expected…like after doing NEAP/Lisachem papers, I anticipated an exam that wasn’t so easy to mess up yet still tested our entire knowledge on the course.
James | Jun 13, 2010 | Reply
I agree that is is butanol/pentanol
In fractional distillation, the lowest part of the flask is the hottest, therefore as the mixture rises upt he flask,the mixture with the highest boiling point will condense first and be collected first, while the others will continue to rise until the tempreture is cool enough for them to condense.
Therefore if butanol/pentanol where in the mixture they would have condensed and been collected before propanol, which was not the case, therefore it must have been methanol/ethanol in the mixture.
97995555 | Jun 13, 2010 | Reply
yer i think thats wat i got
97995555 | Jun 13, 2010 | Reply
its not this as there were 2 oxygen atoms. i think it was ethyl methanoate. urs was close though
97995555 | Jun 13, 2010 | Reply
yeah? but why?
Paul | Jun 13, 2010 | Reply
James, with fractional distillation, the mixture starts as a liquid at room temperature, and is then heated until the boiling point of the molecule with the LOWEST boiling point of the mixture is reached. This rises up as a gas and then condenses back into a liquid due to the water running through the condenser part of the distillation kit. THEREFORE, if the FIRST fraction was collected at 92.7C that means propanol is the LOWEST boiling point of the mixture, therefore the other substance must be pentanol/butanol – however the question asks which substance must NOT be in the mixture: therefore methanol or ethanol. Fractional distillation starts at a low temperature and then warms up to separate the substances. You are implying that it starts at a high temperature and then cools down to separate the substances.
Brad | Jun 15, 2010 | Reply
I agree with Paul, if the first fraction, propanol, was collected at 92.7 degrees then methanol and ethanol musn’t be in the mixture
Nipun | Jun 16, 2010 | Reply
Chem Exam was easy as
Tee | Jun 16, 2010 | Reply
Anyone notice the mistake in the last question. It stated the melting point of butane as its boiling point and then asked you to justify the difference in comparison to propanol.
Mercury | Jun 16, 2010 | Reply
I did the exam in China,and I thought it was quite easy,though I made two silly mistakes.
michelle | Jun 18, 2010 | Reply
well done for pointing that out Tee! You’re right, I googled it and the boiling point of butane is actually -0.5 degrees celcius, not -138.4 degrees celcius (which is its melting point)
I didn’t even notice that! Although the point of the question isn’t really changed, since the boiling point of propan-1-ol is still higher.
Cinnamon | Jun 24, 2010 | Reply
You don’t get consequential marks for explanation questions – only calculations. You can not have a correct explanation for an incorrect answer. This is in regards to the fractional distillation Q. Correct ans = methanol/ethanol. So if you said anything other than those 2 you lost 2 marks.
lol | Jul 31, 2010 | Reply
yea
yay
***** | Aug 2, 2010 | Reply
so how did everyone go? i got a C+
Leah | Aug 2, 2010 | Reply
Oh I got a B.
C+ is still good.
Ted | Aug 2, 2010 | Reply
I got a c+ >.< i thought i did well..
Most people got a c
***** | Aug 2, 2010 | Reply
im so upset. is there any chance i can get a 35
Sandra | Aug 3, 2010 | Reply
I got a B and I’m soo absolutely over the moon. It’s a miracle!
bob | Aug 3, 2010 | Reply
holy smack i got a c tis crazy
Anon | Aug 3, 2010 | Reply
A+
-- | Aug 3, 2010 | Reply
I got a C+ too =(
You just need to work harder for Unit 4
I need to do much better on the next exams for chem AND physics plus my other subjects, eep!
bobjr | Aug 4, 2010 | Reply
i thought i’d fail
throughout the year chem was always smack bang hard
felt so stupid especially by the top students
turns out i got just the same as them a B+
cop that
xoxo
Sandra | Aug 4, 2010 | Reply
everyone in my school got an A and i got a c fml and shoot me now
Gugli | Aug 5, 2010 | Reply
A+
Gugli | Aug 5, 2010 | Reply
apparently you could only afford to lose 7 marks to get an A+!!
would’ve much preferred last year’s exam!
M | Aug 5, 2010 | Reply
C? C is crazy? Try a D. A big fat one. >.<
sucrose | Aug 9, 2010 | Reply
B….
is it possible to get high 40′s or 50 with that?
=.=
EJ | Aug 11, 2010 | Reply
impossible to do raw even if you smashed the sacs and final exam. a friend of mine got a+ a a last year and pulled a 41 raw.
sucrose bottle | Aug 11, 2010 | Reply
A+ repp ;D
But really, it was a simple exam and a hard one to do well in. Get my statement of results tomorrow