2015 A Level H2 Chemistry Paper 1, 2, 3

last SG · 2015-11-06T20:43:51+00:00

History students!! Do check out my site for notes that will guarantee you an A in H2 History :) pass on the message to all who are struggling with this subje...

MadForChemistry SG

Hi , for the question about distiguishing between Br- and Cl-, I used the displacement method by adding Cl2. However for the observation, I stated that reddish brown gas of Br2 will be seen instead of a reddish brown solution. How many marks will I get? Thanks!

UltimaOnline SG

Was it a 1 or 2 mark question? If 2 marks, you get 1. If 1 mark, you get 0.

MadForChemistry SG

It was a 3 mark question.

UltimaOnline SG

It was a 3 mark question.

Then you should get 2 marks (assuming you wrote everything else correctly).

SBS n SMRT SG

ultima this year you still taking as private candidate?

UltimaOnline SG

ultima this year you still taking as private candidate?

Why u ask leh? U also want ah?

UltimaOnline SG

Feel free to discuss the P3 questions here in this thread after the paper tomorrow! As always, I'll only comment on your answers, instead of giving out full model answers. Because the question paper for P3 can be taken back, within hours many JC teachers and private tutors will be releasing their own solutions. You can always check against their answers, and any questions or concerns, you can ask me here.

Have fun with P3 tomorrow! ;Þ

UltimaOnline SG

So did you find P3 easy or tough? How about your classmates / schoolmates? Which question did you skip?

Overall, I'd say this P3, like P2, is neither particularly easy nor tough. So the A grade boundary thus far (excluding P1) should be approximately 72.5%, give or take 1%. If P1 is surprisingly easy or tough, then the A grade boundary may be increased or decreased, up to 2% or so.

poq9 SG

Did 1,2,3,4 only didn't know how to derive the mechanism for q4 lol

Other than that everything else was good!

Weihaw08 SG

It was quite easy :P

nelexus SG

Not really sure of the mechanism for Q4d (i).

Question says first order with respect to H+ and HMF itself, so i guess the slow step has to involve both H+ and HMF. all i can think of slow step is the subsequent loss of H2O as a leaving group as an Sn1, which i think is reasonable because the carbocation generated is stabilised by resonance away. this means hmf is part of the slow step (the rate determining step) but i couldn't incooperate the H+ in the slow step. not really sure how it goes

UltimaOnline SG

A common groan I hear from students is, "Q5 looks tough at first glance but only after the paper then I realized it's actually the easiest question! So wasted!". True, but one little risk with Q5, is that there are parts d & e, hidden on the last page (ie. the qn looks like it's 2 pages long, but it's actually 3 pages long), and some students didn't realize this, skipped parts d & e, and lost 7 marks.

Some students found P3 easier than P2, while others found P2 easier than P3 (mainly because for many students the time constraints pose more of a problem for this year's P3 compared to P2). I'd say overall P2 and P3 are both of average difficulty.

So weaker students are now hoping P1 will be easier, so it'll be easier to pass. Stronger students are now hoping P1 will be tougher, otherwise the A grade boundary may increase from 72.5% to closer to 75%, and it'll be more difficult to get an A grade.

What do *you* wish for? We'll find out next Wed whether your wish will come true. ;Þ

UltimaOnline SG

Not really sure of the mechanism for Q4d (i).

This is indeed the trickiest question out of the entire P3 (and arguably P2+P3 too). Well done, your mechanism is correct. The thing you now need to figure out is, do you know why your mechanism obeys 1st order kinetics for both H+ and HMF? ;Þ

Malachitear SG

Its really something like that? I did what nelexus did and just kinda left it cuz I couldnt figur it out. When you say its correct, is it something simple like the protonated alcohol was considered an intermediate and thus in the rate equation it is represented by H+ and HMF?

Malachitear SG

I was kinda running out of time by question 4 so I was really thankful for that little string of short answer organic questions :D

Lololgirl SG

I can't remember if I arranged the paper in the correct order though...:p

UltimaOnline SG

Yes, spot on, you get your marks ;)

UltimaOnline SG

I can't remember if I arranged the paper in the correct order though...:p

No worries, Cambridge won't penalize u for that :)

Lololgirl SG

Many people stated that paper 3 was very easy and many of them got around 70+/80 (claimed by them). Is it true that we must get >70 marks for the whole of paper 3 to get an A? Thanks.

UltimaOnline SG

Many people stated that paper 3 was very easy and many of them got around 70+/80 (claimed by them). Is it true that we must get >70 marks for the whole of paper 3 to get an A? Thanks.

You must get >75% for overall combined score (SPA + P1 + P2 + P3) to secure your A grade. The actual A grade boundary will be somewhere between 70% to 75%, depending on the bell curve.

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