2014 H2 Chemistry Paper 2, Paper 3 and Paper 1 discussions

last SG · 2014-11-17T21:59:01+00:00

Guys I know this is a chem discussion page but can someone post their answers for Bio MCQ today? :S Think I'm gonna get 33/34 crying

Richard22 SG

I honestly think that this is the easiest mcq I've done (from 2007-2013)

Theres some trap in this yr paper, and the ultimate trap being qn 15. I guess alot of the people would have thought it to be Pcl3, but its actually Alcl3! And from my friends, qn 37 some of them thought C was wrong too.

Anyway, on a side note, A lvl is over!!!!

UltimaOnline SG

Hi could you explain the answer for q7, 21 and 39(why cant there be hbonding in pr structure)

Q7. Both cation and anion have lowest charge densities, hence weakest ionic bonds.

Q21. Diagram indicates SN1, hence X is the transition state of the leaving group being eliminated.

Q39. Primary structure refers to the sequence of amino acids, which are held together by peptide covalent bonds only.

joel tan 123 SG

Hi sir could you please post h1 answers as well. thanks alor

UltimaOnline SG

Hi sir could you please post h1 answers as well. thanks alor

Sorry, I don't have the H1 qn papers. You can look for your H1 school teacher for that.

Matthewsoemoz SG

Ya i agree easiest mcq of all the years! Anyway enjoy your freedom guys!

UltimaOnline SG

Originally Posted by Gaga_ View :
Hello may I ask if the 77% is a lower range estimate or higher range estimate? Higher range estimate being that it almost confirm won't be higher than 77%?

It's a safe estimate. There's a very small possibility it might be higher than 77%, but it's highly unlikely.

If you thought you got > 77% and yet you didn't get A grade, then it's almost definitely your self-marking and self-estimate that is incorrect. For instance, many JC students self-mark their P2 and P3 answers based on their school teachers or private tutors' answers, which has to be taken with a pinch of salt (since it's common knowledge that answers commonly differ between school teachers, both across schools and even within a school).

Originally Posted by EightyOne
Hey Ultima im confused 77% includes SPA?

Yes. Since your school does not release Spa grades, you have to estimate that for yourself. I recommend you play safe and assume you only did so-so for Spa.

stusentxxx SG

Sorry, I don't understand why qns15 is Al?

and why is qns37 A, option 3 I rotate 360degrees but is still unable to get the product structure.

chemrock SG

For question 33 why do the lattice energies have to be take into account? Since the lattice energies of the group II sulfates decrease down the group, taking the LEs might contradict the trend of decreasing solubilities So should the answer be D instead

UltimaOnline SG

Sorry, I don't understand why qns15 is Al?

and why is qns37 A, option 3 I rotate 360degrees but is still unable to get the product structure.

Q15
A says it's a metal, eg. Al
B says its P
C says it's P or Al
D says it's Al

Q37
Look at the 1st product of the E1 (ie. unimolecular elimination mechanism) reaction on the left (the products on the extreme right are the result of a carbocation rearrangement due to hydride shift, which is beyond H2 syllabus).

Momento SG

Are the worked solutions for p2 and p3 out yet?

UltimaOnline SG

By Hess Law, you have to consider *both* the lattice dissociation enthalpies as well as the hydration enthalpies. See my BedokFunland JC question (posted on my BedokFunland JC website) here :

Adelineeeee (: SG

why is q36 option 1 correct?

Immasheep SG

Hi, why option 3 for qn 37 is wrong and why is qn2 not D?

stusentxxx SG

For qns 15, I Don't understand why option D is only applicable for Al, which reaction is it talking about?

For 37, but the product given in the qns is a mirror image of the product given in the diagram above, since the product is not a chiral compound, So wouldn't it not be form?

UltimaOnline SG

Are the worked solutions for p2 and p3 out yet?

Yes, many schools and private tutors have released P2 and P3 full solutions for their own students, but (since you're not their student) you have to search for these solutions on your own. I will not be releasing P2 and P3 full solutions, since I've already answered many P2 and P3 queries here on the forum.

UltimaOnline SG

why is q36 option 1 correct?

Because 3 is obviously wrong and 2 is obviously correct, and there is no option which says "only 2 is correct".

Immasheep SG

Sorry i meant why is qn 3 not D, thanks!

UltimaOnline SG

Hi, why option 3 for qn 37 is wrong and why is qn2 not D?

Option 3 for Qn 37 is right (not wrong, as you wrongly said).

For Q2, you have to write the half-equations and balanced disproportionation redox equation, and the question specifies equal moles of ClO2 and OH- ions in the final balanced disproportionation redox equation.

UltimaOnline SG

Sorry i meant why is qn 3 not D, thanks!

You have to write out the balanced combustion equation for compound G, given as C7H12O3. To balance O atoms, 8.5 molecules required.

enorh12 SG

Hi,

For qn33. Since SO4 is much bigger than M, shouldnt Hsoln LE be counted as insignificant compated to hydration energy. Since the increasing size of M will only affect LE minimally as SO4 is alr so big. My answer was D...

Qn37. My answer was C because the conditions given didny specify excess conc NH3. So polyalkylation likely to take place and primary amines formed will undergo further nucleo sub

Thanks!

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