2016 A Level H2 Chemistry Paper 2, 3, 1 discussions

last SG · 2016-11-08T20:10:45+00:00

I would think they should accept only NO2+S02=SO3+NO then regeneration bla bla blaso its like a homogeneous catalyst and Oxidising agent i would think elect...

liaumel SG

I wrote the part for cis isomers too because I noticed they did write down cis isomers in the data given for the acids. So shouldn't the answer of cis isomers being harder to pack as tightly as straight chain alkyl groups of other acids be correct?

UltimaOnline SG

Zhhh_, Sir3, liaumel and everyone else whose queries were not answered, sorry but

#1 - I honestly forget most of the questions for today's Paper 2 liao, so can't definitely say if your answers are acceptable or exactly how many marks your answer can get.

#2 - Do not be too concerned about calculating your marks this way. Cambridge is more reasonable and less anal than how Singapore JCs mark, and on the other hand, you could have made some other errors or careless mistakes as well, that you don't realize. So no point worrying too much about calculating your own marks for each paper just over.

#3 - Focus on preparing well for your upcoming papers, and for Chemistry, feel free to continue posting your questions on this forum if you need help. Hope everyone who participated in this thread today, would be willing to help each other out on any Chem questions you students might come across while preparing for P3 and P1. Just like how private tutor / school teacher TheFire521 has been very helpful in this thread.

UltimaOnline SG

Will you be spotting the topics for H2 chemistry for paper 3? Thanks

Eh don't try to spot lah, seriously. Don't bother trying to 'outsmart' Cambridge this way. Cambridge can be very guai-lan in setting the topic spread of questions, precisely becoz they know some students will try to 'spot'. For some years, an entire topic can be almost entirely missing from all 3 Papers.

Rather, focus on choosing your 4 out of 5 questions very carefully for upcoming P3, based on your own competence in the various topics (next year onwards, new syllabus, cannot choose liao). So instead of 'spotting' qns to prepare for, *choose* wisely the 4 qns for P3, based on your own topical competencies. That's the only 'spotting' you can do, practically speaking.

And be especially careful if you choose to do Q5 : last year Q1 to Q4 were mostly single-page question, then Q5 suddenly *pom* a 3 page question, and many students who did Q5 totally missed out on the last page, which cost some of them an entire grade.

Sir3 SG

Will you be providing the answers for p2?

UltimaOnline SG

Will you be providing the answers for p2?

No, sorry. For several reasons, not least of all being that even if your answer is different from mine, you could still score some or all the marks. Cambridge is reasonable, and for many questions, may accept alternative answers or phrasings.

Also, I prefer all of you students take this chance (many of you registered today just to post in this thread), to focus on preparing for upcoming papers, and ask any Chem questions you have here.

Even if it's just a couple of days before P3 and P1, but if these last few days (in a way, the last few days are the most crucial few days), you can benefit from being on this forum, asking questions on this forum (and I hope helpful folks such as private tutor / school teacher TheFire521, will continue to participate in discussions and help students out), then well, I'll be glad some of you students would have benefited in preparing for upcoming Papers 3 & 1 in some small way through this forum.

Admittedly, I did start this thread so you guys can ask qns on the Paper, but going forward, I feel it's more helpful if you guys focus on seeking guidance on related concepts, rather than asking "how many marks can I get if I wrote this answer" for Papers already over etc.

UltimaOnline SG

if I forgot to x2 the Mr of Iodine, how many marks will I lose? my answer was 5.70 which was twice of 2.85. question was 4m.

Just in case some of you didn't know, H2 Chem does have 'error carried forward' for calculations.

As stated elsewhere in this thread, I can't remember what the exact questions are, and what the 4 marks are exactly for, and besides you can't reproduce your full answer here either, so I can't say how many marks you will get. But if this is your only error, then you would only have lost 1 mark (for this), naturally, coz your mistake described is only 1 single mistake, and there's error carried forward.

UltimaOnline SG

The question said so, huh? Good for you that you noticed that. But I don't remember the question asking for "why" or "how" having C=C groups change the melting point, only what the effect on melting point is, ie. presence of C=C groups lower the melting point. A giveaway 1 mark.

Private tutor / school teacher TheFire521 has already addressed the other parts of this question.

YOUU SG

It is observed that the rate of substitution of a hydrogen atom in 2,2–dimethylbutane by a chlorine atom is dependent on the type of hydrogen substituted – primary, secondary or tertiary.

The table below shows the relative rate of substitution by chlorine.

Reaction

Type of hydrogen substituted

Relative rate

RCH₃  RCH₂Cl

primary

R₂CH₂  R₂CHCl

secondary

R₃CH  R₃CCl

tertiary

Using the information from the table and by considering the number of hydrogen atoms of each type (primary, secondary or tertiary) within 2,2–dimethylbutane, predict the ratio of the three products L, M and N.

Explain how you arrived at your answer.

ratio of L to M to N: ………………………………………………………..

Heyyoooo SG

Anybody knows roughly the iodine qns ? Like how many grams and stuff ? I wanna recalculate

UltimaOnline SG

Heyyoooo, forgot the values liao.

YOUU, combine both factors (No. of H atoms Substitutable x Reactivity of Pri vs Sec vs Tert H atom) mathematically, for each of the 2 possible products. See 5th bullet of this section.

Thomas00 SG

So is Fire521 a teacher or a student?

UltimaOnline SG

So is Fire521 a teacher or a student?

Either private tutor or school teacher. If he wants to, he's welcome to reveal the name of his tuition center. His posts might help to bring in more students for him.

Kiddo1998 SG

How was paper 3?

UltimaOnline SG

How did you JC students (and tutor/teachers such as TheFire521) find the Paper 3 today? How did your schoolmates find the Paper 3? Which Qn did you not do?

I estimate it's slightly on the tough side, due to 2 out of the 5 Qns being slightly time consuming.

Overall, A grade boundary may be slightly decreased to approx 73% (based solely on difficulty of Papers 2 + 3, not yet considering performance of Singapore cohort, which I would not know).

houdini_00 SG

How did you JC students (and tutor/teachers such as TheFire521) find the Paper 3 today? How did your schoolmates find the Paper 3? Which Qn did you not do?

I estimate it's slightly on the tough side, due to 2 out of the 5 Qns being slightly time consuming.

Overall, A grade boundary may be slightly decreased to approx 73% (based solely on difficulty of Papers 2 + 3, not yet considering performance of Singapore cohort, which I would not know).

It was a really easy paper with straight-forward concepts. But I chose the wrong question and couldn't rectify it in the end which means I lost approximately ten marks there. Still, the rest of the questions were really straight-forward and easy to score at. The one question I'mreferring to is the electrochemistry question with a single mark for each questions. Not easy. The organic there was a killer for me. Regrets.

Kiddo1998 SG

I found paper 3 relatively easier compared to paper 2( though I found paper 2 quite difficult). I did Q1,2,4,5. What is your opinion about these questions,

UltimaOnline SG

houdini_00 and Kiddo1998

Hehe, weird that I seem to be the only one who felt P3 was tougher (ie. more time consuming) than P2. But I felt Q1 and Q3 were the time consuming ones, not Q4.

houdini_00 SG

houdini_00 and Kiddo1998

Hehe, weird that I seem to be the only one who felt P3 was tougher (ie. more time consuming) than P2. But I felt Q1 and Q3 were the time consuming ones, not Q4.

Q3 was the killer, or so I feel. I would have achieved much more if I did Q4 and sacrificed the 4m I couldn'tdo there. Better than losing ten marks in Q3 haizzz

Thefire521 SG

I found paper 3 relatively easier compared to paper 2( though I found paper 2 quite difficult). I did Q1,2,4,5. What is your opinion about these questions,

HI GUYS

This paper is very very doable. It boils down to your carefulness and question choice and also i think bedok funland students will benefit alot from these questions.

I thought people who did question 3 especially the deduction part would be on the losing end because the other questions were more doable. The slightly novel one is the q4 voltmeter.

However if u are careless and gave them tribromo compounds instead of monobromo that they want or if u forgot to pass methane as a gas for the electrochem set up, then its all these careless mistakes that will cause you your marks!

I would say 15/20 should give you a sufficient A. This year moe decided to focus on concepts. If you had all studied learning outcomes one by one this paper is not a kick.

Thefire521 SG

Q3 was the killer, or so I feel. I would have achieved much more if I did Q4 and sacrificed the 4m I couldn'tdo there. Better than losing ten marks in Q3 haizzz

What i did was i completed half of q3. But saw the long deduction question so i just continued with q4 and q5 they were finished in arnd 30 minutes. Why did you not move on to try the rest?

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