H2 Chemistry 2013 'A' Levels P2 & P3 & P1
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Discuss the H2 Chem 'A' level exam questions in this thread, after each of the papers is over.
Paper 2 : tomorrow Tuesday 2pm to 4pm.
Paper 3 : this coming Thursday 2pm to 4pm.
Paper 1 : next next Monday 2pm to 3pm.
Remember to get plenty of sleep (it'll help you more than mugging all night), and a tasty light lunch with sufficient water, before taking the exam paper (if you skip lunch, insufficient glucose in your brain causes your mind to go blank; on the other hand, too heavy a meal causes blood glucose levels to spike, which causes insulin levels to spike, which causes an increase in blood tryptophan, which gets converted into serotonin, which gets converted into melatonin, which makes you sleepy).
Enjoy the H2 Chem Papers! -
So what do *you* personally think of today's H2 Chem Paper 2?
Easy? Normal? Tough?
Any questions feel free to ask and discuss here.
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Originally posted by UltimaOnline:
Discuss the H2 Chem 'A' level exam questions in this thread, after each of the papers is over.
Paper 2 : tomorrow Tuesday 2pm to 4pm.
Paper 3 : this coming Thursday 2pm to 4pm.
Paper 1 : next next Monday 2pm to 3pm.
Remember to get plenty of sleep (it'll help you more than mugging all night), and a tasty light lunch with sufficient water, before taking the exam paper (if you skip lunch, insufficient glucose in your brain causes your mind to go blank; on the other hand, too heavy a meal causes blood glucose levels to spike, which causes insulin levels to spike, which causes an increase in blood tryptophan, which gets converted into serotonin, which gets converted into melatonin, which makes you sleepy).
Enjoy the H2 Chem Papers!I think its quite a normal paper.. but the planning wasnt smth I expected :(
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what's the transition planning about? any stunner questions?
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A few hours left to 2013 H2 Chem Paper 3...
If you have the time, revisit all the Deductive Elucidation type of questions (both Organic and Inorganic) from the past 3 years (2010, 2011, 2012) of Singapore A levels H2 Chem Paper 3s. Today's paper will likely include questions similar to these.
If you've not yet done so, check out my list of BedokFunland JC questions here :
http://www.infinity.usanethosting.com/Tuition/#BedokFunlandJC_Chemistry_Qns -
Thought paper 2 was really manageable but paper 3 had really lots of explanation and very little calculation... Feel kinda insecure about that :/
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P2 and P3 are of similar difficulty. Considering how all the JCs have been preparing their students for super killer papers, the bell curve this year might turn out weird. Possibly, you may need approx 75-80% to secure a distinction 'A' grade.
Anyway, you should spend the next few days left before P1, doing all the Singapore JCs 2013 Prelim paper 1s; any questions feel free to ask about them here.
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75-80% is rather scary...
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BedokFunland JC's 2013 H2 Chemistry Paper 1 Answers :
If you disagree with any of the Answers I've provided here, please post your own answer, including your reasoning for them.
Q1 - B
Q2 - B
Q3 - D
Q4 - C
Q5 - A
Q6 - C
Q7 - A
Q8 - B
Q9 - D
Q10 - C
Q11 - D
Q12 - B (NO2 is a radical which damages the ozone layer, but thinning of ozone layer *reduces* global warming, not increases it! It's true that NO2 is a greenhouse gas, but it's not one of the most common or one of the most damaging greenhouse gases. Acid rain from both HNO3 and H2SO4 (for which NO2 indirectly catalyzes the formation of) is probably a greater concern than global warming, in the context of NO2. NO2 catalyzes oxidation of SO2 to SO3, which undergoes hydrolysis to form H2SO4.)
Q13 - D
Q14 - D
Q15 - B
Q16 - D
Q17 - D
Q18 - A
Q19 - C
Q20 - C ( X and Z are solely sp2-sp2 overlap, while W and Y have partial and full pi bonding respectively (for this resonance contributor anyway; the resonance hybrid actually has partial pi bonding for all the bonds) ; since there's no X and Z option, so yes the best answer is C - all bonds are sp2-sp2 overlap ... + some unhybridized p orbital overlap actually)
Q21 - C
Q22 - D
Q23 - B or D (debatable but more arguably B ; since temperature, duration, extent of hydrolysis not specified)
Q24 - B
Q25 - B
Q26 - B
Q27 - C
Q28 - C
Q29 - A
Q30 - D
Q31 - A
Q32 - D
Q33 - A
Q34 - B (tricky : the OS of Grp II metal does not change, but oxygen undergoes disproportionation)
Q35 - D
Q36 - B
Q37 - A
Q38 - B
Q39 - C
Q40 - A (the mechanism involved for this condensation reaction, is nucleophilic addition-elimination). -
Hi sir,
For question 12, why is the answer C? Since the part about thinning of ozone layer doesn't directly address global warming. I put D, haha.
For question 20, why is D more likely than C?
For question 24, why is it C not B? I put B since the 2-hydroxypropane P has a lowe Mr than the nitrile compound R...right? haha.
On a side note, how much do you think a student will need to get A for this MCQ paper?
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Hi for Qn 24 shldnt it be B?
Initial Mr of CH3CHBrCH3=123
P=CH3CH(OH)CH3=60
Q= CH2=CHCH3 =42
R=CH3CH(CN)CH3=69'
so from lowest to highest is Q P R=B
And for 40 shldnt it be C cos 1 is jus a condensation reaction
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wouldn't option 1 for 40 be correct though? even though it is condensation, N of the hydrazine would still have to attack the carbonyl carbon to form a tetrahedral intermediate before it leaves as water to form the imine?
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Hi, I just saw the paper 1, and I was wondering whether q23 is either B or D. Because the question never stated whether heating with NaOH (aq) was under reflux, so B may not produce the highest amount of Cl- anions at the end. Just asking whether D is a more possible answer.
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Originally posted by Onionringman:
wouldn’t option 1 for 40 be correct though? even though it is condensation, N of the hydrazine would still have to attack the carbonyl carbon to form a tetrahedral intermediate before it leaves as water to form the imine?
Ahh ok i got what u mean, Thanks! :D hmm yeah for 20 i put C as well since bezene is made up of sp2 carbons
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Onionringman, yes you're right, Q12 - B (thinning of ozone layer reduces global warming, tricky lol!). Thanks for pointing out my mistake.For Q20 - D or C (debatable, but more arguably D ; the C-C benzene bond is a partial double bond, formed not just from the overlap of sp2 and sp2, but also from the overlap of p orbitals for the partial pi bond)Q24 - B (doh... order of molar masses, not boiling points... my bad)Overall, this years cut off score on the bell-curve for A grade should be between 73-75%.Edification, it's true that "heating" alone without reflux is ambiguous, but it's still sufficient for hydrolysis. The temperature and duration isn't stated, even with "reflux", so there's always ambiguity anyway.
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for qn 23, shouldnt answer be D based on ease of hydrolysis. where acyl chlorides hydrolyse more easily that alkyl chlorides. hence, it is likely that a higher yield of AgCl will be gotten from D
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Originally posted by lolol233431432:
for qn 23, shouldnt answer be D based on ease of hydrolysis. where acyl chlorides hydrolyse more easily that alkyl chlorides. hence, it is likely that a higher yield of AgCl will be gotten from D
True, this question is ambiguous. It didn't state whether the reaction was complete or not. If it had stated "after 1 min" etc, then the answer would definitely be D. -
for question 12, i feel that NO2 does not catalyse th reaction, it merely forms acid rain. NO2 + h20 = HN02 + HNO3
even at same temp, acyl chloride should still hydrolyse faster. assuming same amount of time, yield from acyl chloride should be higher.
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Originally posted by lolol233431432:
for question 12, i feel that NO2 does not catalyse th reaction, it merely forms acid rain. NO2 + h20 = HN02 + HNO3
even at same temp, acyl chloride should still hydrolyse faster. assuming same amount of time, yield from acyl chloride should be higher.
Q12 - I've already edited the answer list.Qn 23 - it didn't specify % yield if reaction is incomplete, it implied reaction is complete for all options (except C, which requires exceptionally high temperatures and pressures).
But as I said, this qn (together with a couple of others) is ambiguous, so it's anyone's guess which answer Cambridge prefers.
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Hi, does anyone have the suggested solutions for the H1 Chemistry paper 1?
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ah ok peace peace. so for 12, do you feel th answer should be D instead? since for B NO2 catalyses th reaction, but in fact it does not right? it jus forms acid rain
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Q33, just wondering, why must the hydrogen gas be dry; the rationale behind the choice?
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understandard conditions, H2 must be 1atm, if it is not dry h2 will not be pure and that 1atm of gas may consist of other gases.
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anyone can explain to me how does NO2 catalyse So2 in question12?
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Uhh, dont you find it quite presumptuous, since they never limit the amount of gas found in the environment, so for all we know H2 could still be at 1 atm?