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2017 H2 Chemistry JC1 & 2 students post your questions here

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  • Moderator
    H2 Chemistry @ BedokFunland JC (near VJC & TJC)
    UltimaOnline's Avatar
    13,415 posts since May '05
    • Taiwan : http://wenr.wes.org/2016/06/education-in-taiwan

      Indonesia : https://link.springer.com/article/10.1007/BF00598171

      Malaysia : http://multilingualmania.com/english-or-national-language-thoughts-from-malaysia/

      Hong Kong : http://www.scmp.com/lifestyle/family-education/article/1583037/argument-continues-over-using-cantonese-or-putonghuaM

      Are you kidding? The best language of instruction (eg. when learning Chemistry, Physics, Biology, Medicine, etc) is obviously English, the lingua franca of the world, in order to effectively communicate with the rest of the world (ie. not just with America ; for instance in Europe, the many different Europeans all have their own distinct mother tongue language, but almost all are at proficient in English for the sake of communication with the rest of the world). Having English as the language of instruction has conferred the single most important educational advantage Singapore has had over other Asian countries (eg. Malaysia, Indonesia, Taiwan, Hong Kong, etc), and as Singapore's bilingual policies have proven, does not necessarily require sacrificing your mother tongue or ethnic culture altogether.

    • A BedokFunland JC H2 Chemistry Challenge

      99% of Singapore JC students will get this wrong, and about 50% of private tutors and school teachers will get this wrong.

      Calculate the pH of 1.0 x 10^-8 mol/dm3 of HNO3.

      Go ahead and calculate it, and if you like, post your final answer here to 3 decimal places (note : don't show your working, coz in case you get it right, don't ruin the fun for others). I'll only state if your final ans is correct or wrong, nothing more nothing less.

      Edited by UltimaOnline 06 Jul `17, 7:37PM
    • ...take on the Singapore Education System, and on being a student in Raffles Junior College. It's a pity the video has since been taken ... time to hear my story. I was from Victoria School (VS) and Raffles Junior College (RJC). Growing up, I was taught to work ...

      Edited by UltimaOnline 06 Jul `17, 11:12PM
    • If you (as a JC student) found RJC Kevin Wee's personal story inspiring or at least helpful to you in some way, you might also be interested in hearing HCJC Xin Lin's story as well. She too, was stressed out by the life as a student in an elite JC, but in case you're wondering, she didn't burn her A level certificate.

      image

      Truth behind my JC life :

      https://stopthe-pretence.blogspot.sg/2012/03/truth-behind-my-jc-life.html

    • Seriously, no takers for my challenge?

      To elaborate, barring any silly mathematical errors, there are only 3 possible answers commonly given, depending on your level of Chemistry conceptual understanding : the U grade answer, the D grade answer, and the A grade answer. Based on your answer, I'll assign you your grade.

      A BedokFunland JC H2 Chemistry Challenge

      99% of Singapore JC students will get this wrong, and about 50% of private tutors and school teachers will get this wrong.

      Calculate the pH of 1.0 x 10^-8 mol/dm3 of HNO3.

      Go ahead and calculate it, and if you like, post your final answer here to 3 decimal places (note : don't show your working, coz in case you get it right, don't ruin the fun for others). I'll only state if your final ans is correct or wrong, nothing more nothing less.

    • Only 2 more weeks before the Special (Permanent) Discount Offer for JC2 students expires. I won't be offering any more such discount offers after July.

      image

    • Although the new H2 Chemistry syllabus specifies only a qualitative treatment of the Nernst equation is required, but you can bet your ass that most JCs will set Prelim paper questions on a quantitative treatment of the Nernst equation, and so will Cambridge, afterall what better way to illustrate a qualitative understanding than to perform calculations quantitatively?

      I have an extensive collection of Nernst equation problems ready for my BedokFunland JC students. All other students can go ask their school teacher or private tutor for practice on Nernst equation problems, and/or go Google out such Nernst equation problems on the internet for yourself to practice on. Have fun! :)

      imageimage

      https://en.wikipedia.org/wiki/Nernst_equation

      Edited by UltimaOnline 10 Jul `17, 11:13PM
    • A BedokFunland JC Original H2 Chemistry Challenge

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    • Now that the Mid Yr exams are over, if any of you JC students would like to share with us any particularly sadistic or guai-lan H2 Chem question from your Mid Yr exam, pls feel free to do so here ;Þ

      Or, if you disagree with your school teacher on any Mid Yr exam qn, you can ask me for a 2nd opinion here (just like how if a pediatrician gives your toddler a suspicious diagnosis, you might like to consult another specialist for a 2nd opinion).

    • [H2 Chemistry] - "Why or how do acid attacks cause disfigurement?"

      Such a simple Chemistry question with such an obvious answer, but you'll be surprised most JC students don't know the answer. And if you protest, "But acid attacks are not in the H2 syllabus!", my retort is : if you've truly educated yourself in Chemistry, it means to intelligently apply whatever you've learnt within the syllabus, to novel contexts beyond the syllabus. So yeah, certainly expect to have Cambridge do this for Chemistry as well, coz it would be totally unfair and a bloody shame if H2 Chemistry and/or H2 Physics loses to H2 Biology in this didactic, pedagogical, examinational characteristic :

      There will be one or more stimulus materials which may be taken or adapted from a source such as a scientific journal or book which may not necessarily relate directly to the content of the syllabus. Questions may require candidates to explain terms used in the passage, analyse data, justify decisions, perform calculations and draw conclusions based on information in the stimulus material.

      image

      Acid attack first aid: What you need to do immediately to help victims

      https://sg.yahoo.com/news/acid-attack-first-aid-immediately-131700262.html

      Edited by UltimaOnline 15 Jul `17, 5:21AM
    • Last 2 weeks before my Special Permanent Discount offer for 2017 JC2 students expire, and this Special Permanent Discount will no longer be offered after July 2017.

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      Edited by UltimaOnline 22 Jul `17, 3:48AM
    • Last week of July left before my Special Discount Offer for 2017 JC2 students expires!

      --------------------------------------------------------------------------------------

      Watch the following video first, then answer my questions below :

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      https://www.youtube.com/watch?v=ShwH-B9FKNQ

      --------------------------------------------------------------------------------------

      image

  • MapPwner's Avatar
    100 posts since Aug '15
    • Can i just ask whether the hardest H2 chemistry topic in the syallabus is Ksp(Solubility Product)?Because out of all the chapters that is the only chapter i face quite some problems comprehending whereas for the rest is pretty much simple and easy to understand.

  • Moderator
    H2 Chemistry @ BedokFunland JC (near VJC & TJC)
    UltimaOnline's Avatar
    13,415 posts since May '05
    • Originally posted by MapPwner:

      Can i just ask whether the hardest H2 chemistry topic in the syallabus is Ksp(Solubility Product)?Because out of all the chapters that is the only chapter i face quite some problems comprehending whereas for the rest is pretty much simple and easy to understand.


      Yes indeed, Ksp questions can potentially be the toughest topic.

      Feel free to ask for help here with specific Ksp questions your JC may give you. Do include the given solution (either type out or take a photo of the qn and upload the image to your social media account to link here), if available. Then ask me exactly what about the question or solution that you don't understand.

      If it's a TYS or Prelim paper qn, just specify the paper, eg. RJC 2016 P2 Q3, no need to type out or upload the photo of the qn.

      Edited by UltimaOnline 22 Jul `17, 6:33AM
    • Here are a couple of my (BedokFunland JC) Ksp questions that H2 Chem students intending to score a distinction A grade for the A levels need to be able to do, but most Singapore JC H2 Chem students struggle to solve.

      image

      image

      Last week of July left before my Special Discount Offer for 2017 JC2 students expires!

      Edited by UltimaOnline 22 Jul `17, 3:50AM
  • MapPwner's Avatar
    100 posts since Aug '15
    • The AgSCN,AgBr question seems rather mind-blowing and hard to understand but the 1st question for ammonia and ammonium ion question was understandable.

  • Moderator
    H2 Chemistry @ BedokFunland JC (near VJC & TJC)
    UltimaOnline's Avatar
    13,415 posts since May '05
    • Originally posted by MapPwner:

      The AgSCN,AgBr question seems rather mind-blowing and hard to understand but the 1st question for ammonia and ammonium ion question was understandable.


      That's good on both counts. Good that you found the 1st question to be understandable (already making you above average for H2 Chem students, most of whom would struggle with even the 1st question). And good that you found the 2nd question to be mind-blowing, because it means you truly understood it and appreciated its complexity. Most H2 Chem students don't even recognize its complexity or even understand the question. You're doing ok. Keep it up.

  • MapPwner's Avatar
    100 posts since Aug '15
    • Have another question though,if you have the PJC MYE paper 2016 or 2017,do you feel that the difficulty of this paper is comparable/near to that of A levels?

      My school's HOD reprimanded the cohort for this year's dismal performance for MYE as they felt that the standard of the paper they set this year is easier than 2016(I agree a bit but if I did the last year paper I would have probably scored higher).I personally felt that my school paper(with exception of P3 and P1),was slightly below A level standard or almost comparable,whereas P3 and P1 is comparable to A levels.Do you consider scoring 73% total for the chem paper 2017(including P4 prac) as a whole good?

      My school results were:

      A:31 students B:60 students Cohort size:434 students

      MSG:4.2  50th percentile(mean) score:51.11

      Edited by MapPwner 22 Jul `17, 7:24PM
  • Moderator
    H2 Chemistry @ BedokFunland JC (near VJC & TJC)
    UltimaOnline's Avatar
    13,415 posts since May '05
    • Originally posted by MapPwner:

      Have another question though,if you have the PJC MYE paper 2016 or 2017,do you feel that the difficulty of this paper is comparable/near to that of A levels?

      My school's HOD reprimanded the cohort for this year's dismal performance for MYE as they felt that the standard of the paper they set this year is easier than 2016(I agree a bit but if I did the last year paper I would have probably scored higher).I personally felt that my school paper(with exception of P3 and P1),was slightly below A level standard or almost comparable,whereas P3 and P1 is comparable to A levels.Do you consider scoring 73% total for the chem paper 2017(including P4 prac) as a whole good?

      My school results were:

      A:31 students B:60 students Cohort size:434 students

      MSG:4.2  50th percentile(mean) score:51.11


      I don't have MYE papers, only Prelim papers. So I can't comment on your PJC paper or your results for that paper.

      Your school MYE performance by grades are typical for most JCs, because i) JCs try to do u students a favour by setting tougher papers and marking more strictly compared to A levels, and ii) most JC students are still not adequately prepared for A levels at this stage.

      If 73% is your overall score for the upcoming 2017 TYS A level exam, assuming the bell-curve doesn't deviate too significantly from the past few years, you'll have approx 50% chance of scoring A grade (just as you yourself have correctly noted the grade boundaries for H2 Chem, subject to the bell-curve). But most students tend to over-count their own marks, not realizing they've made either careless mistakes, or that Cambridge may penalize them for some of their answers' phrasings (which they blindly memorized from their school lecture notes, which may not be fully acceptable by Cambridge, or which may need to be further adapted to the question at hand).

      Edited by UltimaOnline 22 Jul `17, 7:40PM
  • MapPwner's Avatar
    100 posts since Aug '15
    • Originally posted by UltimaOnline:


      I don't have MYE papers, only Prelim papers. So I can't comment on your PJC paper or your results for that paper.

      Your school MYE performance by grades are typical for most JCs, because i) JCs try to do u students a favour by setting tougher papers and marking more strictly compared to A levels, and ii) most JC students are still not adequately prepared for A levels at this stage.

      If 73% is your overall score for the upcoming 2017 TYS A level exam, assuming the bell-curve doesn't deviate too significantly from the past few years, you'll have approx 50% chance of scoring A grade (just as you yourself have correctly noted the grade boundaries for H2 Chem, subject to the bell-curve). But most students tend to over-count their own marks, not realizing they've made either careless mistakes, or that Cambridge may penalize them for some of their answers' phrasings (which they blindly memorized from their school lecture notes, which may not be fully acceptable by Cambridge, or which may need to be further adapted to the question at hand).

      Ah I see ok.

      I figured if I didn't rush through the paper as I just wanted to finish the paper within time limit and more concerned for my p3(I was reading bio the day before as I was tired of chem),may have done much better due to presence of many errors,whereby eliminating them 80% could even be possible.

       

       

  • Moderator
    H2 Chemistry @ BedokFunland JC (near VJC & TJC)
    UltimaOnline's Avatar
    13,415 posts since May '05
    • Originally posted by MapPwner:

      Ah I see ok.

      I figured if I didn't rush through the paper as I just wanted to finish the paper within time limit and more concerned for my p3(I was reading bio the day before as I was tired of chem),may have done much better due to presence of many errors,whereby eliminating them 80% could even be possible.

       

       


      Overall 80% is ideal and sufficient to safely secure an A grade for H2 Chem, even allowing for a couple of % points overestimated by the over-confident student. Truth be told, after the bell-curve processing, the A grade boundary has never reached 80% for H2 Chemistry, and in most years, a 75% is sufficient for an A grade. The main problem, as I mentioned previously (and many times in previous years), is that over-confident students frequently over-estimate their own marks, eg. assuming Cambridge will mark the same way as their JC teachers.

      Edited by UltimaOnline 22 Jul `17, 8:18PM
  • MapPwner's Avatar
    100 posts since Aug '15
    • Originally posted by UltimaOnline:


      Overall 80% is ideal and sufficient to safely secure an A grade for H2 Chem, even allowing for a couple of % points overestimated by the over-confident student. Truth be told, after the bell-curve processing, the A grade boundary has never reached 80% for H2 Chemistry, and in most years, a 75% is sufficient for an A grade. The main problem, as I mentioned previously (and many times in previous years), is that over-confident students frequently over-estimate their own marks, eg. assuming Cambridge will mark the same way as their JC teachers.

      Yep I know I even tried estimating my scores for individual components before determining my overall %,which i estimated to be 70%.

      I estimated P1 to be 24/30,P2 56/75,P3 52/80,P4 30/40.

      Got my paper back,it was 19/30 for P1,P2 55/75,P3 58/80,P4:31/40,overall 73%.So my estimation was a bit off for P1 and P3.

  • supercat's Avatar
    32 posts since Jul '16
    • Hi there, I'm revising my A level chem + learning higher level chem to prepare for a chem test so I can exempt from chem mods. I have this question to ask.

      Which of the following compounds would react most rapidly with NaCN?
       
      a. 1-bromobutane
      b. (R)-2-bromobutane
      c. (S)-2-bromobutane
      d. 1-bromo-2-methylpropane

      My deduction is that either a or d is the answer, since b and c are technically the same compound (except the direction)

      Now, how do I know which will react faster? a has 1 R group, compared to d which has 2 R groups. I feel that d is more stable and so d would react most rapidly with NaCN. Am I right?

       

  • Moderator
    H2 Chemistry @ BedokFunland JC (near VJC & TJC)
    UltimaOnline's Avatar
    13,415 posts since May '05
    • Originally posted by supercat:

      Hi there, I'm revising my A level chem + learning higher level chem to prepare for a chem test so I can exempt from chem mods. I have this question to ask.

      Which of the following compounds would react most rapidly with NaCN?
       
      a. 1-bromobutane
      b. (R)-2-bromobutane
      c. (S)-2-bromobutane
      d. 1-bromo-2-methylpropane

      My deduction is that either a or d is the answer, since b and c are technically the same compound (except the direction)

      Now, how do I know which will react faster? a has 1 R group, compared to d which has 2 R groups. I feel that d is more stable and so d would react most rapidly with NaCN. Am I right?

       


      This is still considered an A level Chem qn, so I'll help you out here. Once you do Uni level Chem proper, you can post your Uni Chem qns at The Chemical Forums, as my professional interest (as Mr BedokFunland JC) is specifically targeted at A level Chem only.

      Options A and D are both primary alkyl halides (your thinking that Option D is a secondary alkyl halide is incorrect : only if Option D was 2-bromo-2-methylpropane, then it would be tertiary, and 1-bromo-2-methylpropane is still primary), hence the electronics factor is similar. Therefore, the least sterically hindered Option A would be the fastest.

      For Options B and C, apart from your correct deduction that optical isomerism is irrelevant to the rate of reaction, let's consider them for the sake of comparison with Options A & D. Even though electronics would favor the secondary alkyl halides Options B & C for SN1 (over primary alkyl halide Options A & D), but the strong NC- nucleophile would favor SN2 anyway. Hence being SN2, Option A is fastest, followed by Option D, with Options B and C the slowest.

      If instead of 1-bromo-2-methylpropane, 2-bromo-2-methylpropane was specified for Option D (which was what you were prolly thinking of), then Option D (tertiary) would be faster than B & C (secondary) only if SN1 was favored (ie. weak nucleophile, and preferably protic solvent). Since SN2 is favored (ie. strong nucleophile, preferably aprotic solvent) in this question (although the solvent isn't specified by the question), then if Option D was 2-bromo-2-methylpropane, Option A (primary) would still be the fastest (even moreso than Option D being 1-bromo-2-methylpropane), followed by Options B & C, with Option D the slowest (due to greatest steric hindrance).

      Note that we've only considered nucleophilic aliphatic substitution SN1 and SN2 here, rather than elimination E1 and E2 (since solvent and temperature weren't specified by the question). If E1 and E2 are to be considered, a primary alkyl halide in an aprotic solvent with a strong Bronsted-Lowry base such as the NC- anion would favor E2 over E1, while a tertiary alkyl halide in a protic solvent with a weak Bronsted-Lowry base would favor E1 over E2.

      Edited by UltimaOnline 23 Jul `17, 9:53PM
    • If you can't solve my original BedokFunland JC H2 Chemistry challenge question below, try asking your school teacher or private tutor.

      image

      Edited by UltimaOnline 23 Jul `17, 11:08PM
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