VCE Chemistry 2010 Unit 3 Exam Suggested Solutions

[Blakhitman]

but it's 0.06 away from the other. Don't they ALL have to be within 0.05??

[superflya]

What I don't get is how 22.03 is concordant with the others?

it was the 2nd titre that wasnt concordant.

but it's 0.06 away from the other. Don't they ALL have to be within 0.05??

[10weid]

okies..MAO:

% mass at end of Q1 is 3.81%, it is 3.07/80.50=3.8136....
and im fairly certain u didnt have to specify the carbonyl gorup, merely had to say the atoms and the bond type, so had to say C=O results in absorption band at 1750cm-1....

[jimmy999]

And yes, the style of this exam is very different to other past exams. I think this year a few academics at Monash helped out in writing the exam, the style is very similar to Prof. Morrison's exams. [Incidentally, he's an assessor this year, and also incidentally, he made the chemical detectives program. Go him.]

Yes I did have Richard and he did say he was writing this years exam. Hopefully he writes my exam in a way like this

[Blakhitman]

What I don't get is how 22.03 is concordant with the others?

it was the 2nd titre that wasnt concordant.

but it's 0.06 away from the other. Don't they ALL have to be within 0.05??

serious?? I always thought is was 0.05???

[zzzzzz]

yeh i thought it was +_ 0.05 =S

[akira88]

but it's 0.06 away from the other. Don't they ALL have to be within 0.05??

THATS WHAT I THOUGHT.
Because if they're 0.05 from each other, eg. you could have this as concordant:
22.05, 22.10, 22.15,22.20 etc, but yet 22.05 and 22.20 are .15 off :S
and I thought it was 0.05, not 0.1 off :S
I think different textbooks say different things >.<

[clumsy_culhane]

Mao can you explain your reasoning behind your answer of 2 for the question: "The signal at 1.3 ppm is split into a triplet. What is the number of equivalent protons bonded to the adjacent carbon atom?" (Page 13)

[VeryCrazyEdu.]

i think it is .05 between each one but .01 OVERALL...

EDIT: wwoooooooppss i meant .1 overall haha not .01

[andy456]

I was taught 0.1

[superflya]

2 H's in adjacent env.

[crayolé]

Mao can you explain your reasoning behind your answer of 2 for the question: "The signal at 1.3 ppm is split into a triplet. What is the number of equivalent protons bonded to the adjacent carbon atom?" (Page 13)

n+1 rule
3 peaks means it's got two adjacent hydrogens

[clumsy_culhane]

Mao can you explain your reasoning behind your answer of 2 for the question: "The signal at 1.3 ppm is split into a triplet. What is the number of equivalent protons bonded to the adjacent carbon atom?" (Page 13)

n+1 rule
3 peaks means it's got two adjacent hydrogens

But to form splits in the peaks, the hydrogens have to be in different environments , i.e. in non-equivalent environments. Which means there are zero protons bonded to the adjacent carbon that are equivalent.

From KBT solutions :"If the hydrogens of a particular environment have n neighbouring, non-equivalent hydrogens,
the peak from that environment will be split into n+1 component peaks.
Keep in mind that the word ‘neighbouring’ as it’s used above means ‘on the adjacent carbon
atom’. ‘Non-equivalent’ means ‘not of the same environment’."
(http://www.kbtlectures.com/wp-content/uploads/2010/04/KBT_unit3chemistry_trialexamsolutions.pdf)

[jimmy999]

okies..MAO:

% mass at end of Q1 is 3.81%, it is 3.07/80.50=3.8136....

If you bring the exact values through on the calculator, you end up with 3.82% which is the actual correct answer. However if you use sig figs through the question you get 3.81%. Hence I think they will allow both answers

[VeryCrazyEdu.]

okies..MAO:

% mass at end of Q1 is 3.81%, it is 3.07/80.50=3.8136....

If you bring the exact values through on the calculator, you end up with 3.82% which is the actual correct answer. However if you use sig figs through the question you get 3.81%. Hence I think they will allow both answers

yeah...they have allowed both answers in previous exams...