VCAA 2012 Chemistry Unit 3 Exam Discussion

[charmanderp]

Which states?

[acinod]

Sorry accidentally troll-voted 'medium' 

But anyways, having passed VCE already I can't really judge how easy/tough the exam is.

After reading the paper, I honestly thought the exam was quite easy compared to previous years.
Multiple choice was especially easy since only 25% of it included simple calculation questions and the rest was theory that you easily do during reading time to save yourself a lot of time.
The short answer was quite different from previous years because there were A LOT of 1 mark questions, which could work for or against many students. I say this because it's easy to lose marks but also easy to scab marks.

Overall the exam was a lot different from previous exams. Doesn't really have a VCAA feel to it for some reason.

Here's what I got for MC:
1.B
2.C
3.D
4.B
5.D
6.A
7.C
8.D
9.A
10.A
11.A
12.C
13.C
14.B
15.B
16.C
17.D
18.C
19.B
20.D

Shall attempt the short answer now.

[Tonychet2]

I got D for question 5 MC too. What was the answer to last short answer qurstion. Would the concentration be underestimated? the one with the orientation of the amide bonds was a bit hard to explain as well. Do u guys reckon it was easy as 2010, i reckon it was same hardness as 2011. I left out q. 7 cause didn't have enough time and did 8 instead. Was q. 7 tricky?

question 7 was a standard gravimetric analysis question with no tricks

and ouch, what happens if he forgot states on the whole paper? there were lots of write the equation for... questions

would he lose marks on each question or only 1 maximum like sig figs?

[t35t]

I got D for question 5 MC too. What was the answer to last short answer qurstion. Would the concentration be underestimated? the one with the orientation of the amide bonds was a bit hard to explain as well. Do u guys reckon it was easy as 2010, i reckon it was same hardness as 2011. I left out q. 7 cause didn't have enough time and did 8 instead. Was q. 7 tricky?

yes lower than true value because more titre of HCL would be required which means n(HCL) in excess would be higher

therefore n(HCL) reacting with the N(ammonia chloride) would be lower, since N(HCL) reacting = original - a larger number

I thought that if a higher titre of HCL would be required, therefore according to n=Cx V a higher mole of HCl would resullt. As A higher mole of HCL has occured, it would mean that there is less in excess because now-ohhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhh
...
yes. okay..so stupid of me. that's it for me.

[oneoneoneone]

Isn't q12 D? It says the samples were passed through under identical conditions (same pressure, temp, etc), so since its GLC the volume of the 0.2 ug would be twice that of the 0.1 ug sample. Because the spectrum at the top is roughly double the size of the answers below, picking C would have 4* the peak area, when it should just be 2*.

[AllAboutTheLGs]

the stearic acid. i intentionally left it out for last but just forgot to come back to it... FUCK

[nisha]

I forgot sig figs and states. Im done with chem

lol. yea. i feel the same dude. Chem was the subject I dreamed in, the subject I would do to help me relax.

UHHHHG.

[Tonychet2]

Isn't q12 D? It says the samples were passed through under identical conditions (same pressure, temp, etc), so since its GLC the volume of the 0.2 ug would be twice that of the 0.1 ug sample. Because the spectrum at the top is roughly double the size of the answers below, picking C would have 4* the peak area, when it should just be 2*.

its same values just scaled ... i get C

[HERculina]

O damn should have worked faster! thank god i did the kbt exam cause t har a similar question involving errors in back titration. praying that I didn't make a lot of silly mistakes.
the question with obtaining pure propyl propanoate - is it that you add in sodium carbonate and see if it bubbles?

[oneoneoneone]

its same values just scaled ... i get C

But the width on both the large chromatogram and the small one are the same, so the small one has double the time relative to the larger chromatogram.

[sahil26]

Screwed up the last question =/ .... didn't realise it was just a smile back titration question..

What did u guys get for the solubility of NH4CL?

[joseph95]

its same values just scaled ... i get C

But the width on both the large chromatogram and the small one are the same, so the small one has double the time relative to the larger chromatogram.

It doesn't make sense that the retention time would change - the conditions are identical. More of the compound won't change it's retention time - it's characteristic of that compound in those conditions.

At least I think so... 

[horizon]

WHY WERE THE SOLUBILITIES GIVEN? DID WE HAVE TO USE THEM IN OUR CALCULATIONS AT ALL?

[sahil26]

O damn should have worked faster! thank god i did the kbt exam cause t har a similar question involving errors in back titration. praying that I didn't make a lot of silly mistakes.
the question with obtaining pure propyl propanoate - is it that you add in sodium carbonate and see if it bubbles?

i wrote it smells nice

[jadams]

its same values just scaled ... i get C

But the width on both the large chromatogram and the small one are the same, so the small one has double the time relative to the larger chromatogram.

I actually got D too, as i thought it would just be a larger volume injected as a sample....got the same as the above for all other questions, just that one I had different to. (a few mates got c too)