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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
    14,732 posts since May '05
    • I'll help you guys out by giving you the original 4 options in the Singapore JC Prelim P1 MCQ :

      S2F10 (g) < -------- > SF4 (g) + SF6 (g)

      An unknown amount of S2F10 was placed in a 2.0 dm3 flask and heated to 100 oC. The equilibrium [S2F10] was found to be 0.5 M. More S2F10 was then added and the new equilibrium [S2F10] was 2.5 M.

      What is the amount of S2F10 reacted (in terms of Kc), from the 1st equilibrium to the 2nd equilibrium?

      A : (0.5Kc)^0.5 − (2.5Kc)^0.5
      B : (2.5Kc)^0.5 − (0.5Kc)^0.5
      C : (2Kc)^0.5 − (10Kc)^0.5
      D : (10Kc)^0.5 − (2Kc)^0.5

      Edited by UltimaOnline 27 Nov `17, 12:09PM
    • Maybe you guys find that MCQ too easy for you, and can’t be bothered with it. Then how about you guys nominate any MCQ from the 2017 Prelims, that is tougher than that MCQ? Share it with your fellow J2s mah. If you guys bother to discuss, it’s you guys who will benefit. If everyone just lurks lurks lurks, no one bothers to share anything, then you guys are the ones who will lose out (on this opportunity to share and learn together).

    • Fine if no one has any questions anymore, then I’ll just leave it to Mapwner to post the answers to the 2017 P1 here after the paper is over this Wed. Have fun, pple!

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    • Last 24 hours left before P1. If anyone needs any MCQ help, better faster post here. This is your last chance to save yourself.

      Does anyone (eg. mujiaesthetic) still want me to explain how to solve that toughest-2016-Prelims-MCQ? Or all of you solved that one urself liao?

    • Nvm I'll explain it here anyway, in case some of you ask for it later when I'm away from keyboard, and no one else here helps out (though I'm quite sure at least some of you can solve this MCQ, but no one seems to be in a volunteering mood).

      BedokFunland JC Solution :

      Based on the Kc formula, find molarity of either product (since molar ratio of products are 1:1, numerator becomes square of the unknown molarity of either product) at 1st equilibrium = (0.5Kc)^0.5, and at 2nd equilibrium = (2.5Kc)^0.5.

      Convert molarity to moles, you get (2Kc)^0.5 and (10Kc)^0.5 respectively.

      Hence amount of reactant used up = amount of (either) product generated from 1st to 2nd equilibrium = (10Kc)^0.5 - (2Kc)^0.5

      Edited by UltimaOnline 28 Nov `17, 12:13PM
  • delurach's Avatar
    14 posts since Nov '17
    • Hello!! Please help me with this question. Thank you! It's from PJC P1 Q1

      1 Equal volumes of 1 mol dm−3 hydrogen sulfide and sulfur dioxide (each containing a

      different isotope of sulfur) are mixed to precipitate sulfur according to the equations

      shown below:

      H232S(aq) → 32S(s) + 2H+(aq) + 2e−

      34SO2(aq) + 4H+(aq) + 4e− → 34S(s) + 2H2O(l)

      What is the relative atomic mass of the sulfur precipitated?

      A 32.1

      B 32.7

      C 33.0

      D 33.3

  • Moderator
    H2 Chemistry @ BedokFunland JC (near VJC & TJC)
    UltimaOnline's Avatar
    14,732 posts since May '05
    • Originally posted by delurach:

      Hello!! Please help me with this question. Thank you! It's from PJC P1 Q1

      1 Equal volumes of 1 mol dm−3 hydrogen sulfide and sulfur dioxide (each containing a

      different isotope of sulfur) are mixed to precipitate sulfur according to the equations

      shown below:

      H232S(aq) → 32S(s) + 2H+(aq) + 2e−

      34SO2(aq) + 4H+(aq) + 4e− → 34S(s) + 2H2O(l)

      What is the relative atomic mass of the sulfur precipitated?

      A 32.1

      B 32.7

      C 33.0

      D 33.3


      Based on the stoichiometry of the balanced redox, and considering the limiting reactant, the relative amount of products are 2 mol of 32g isotope for every 1 mol of 34g isotope, hence average molar mass of S(s) = (32+32+34) / 3 is your answer.

      Edited by UltimaOnline 29 Nov `17, 3:41AM
  • MapPwner's Avatar
    145 posts since Aug '15
    • Been a long time since I last posted here:

      For me personally,i feel that most school prelim p1 are relatively harder as opposed to the A levels.For instance is not easy to exceed 16-18 marks/30 for VJC/NJC,same for neighbourhood JCs like SRJC paper,where i scored 16 marks which I really didn't bother doing the last few remaining questions i have yet to attempt for that paper as it was really tilting.

      For me,I'm just mainly focusing on TYS P1 questions,which to me are more relatively straightforward,and simple with exception of the last 10 questions(q30-q40) for previous years which are slightly more challenging.For me,scoring 25-27/28-30(Due to some qns not in syallabus) for the first 30 questions is the norm whereas the last 10 questions 5-6/8-10(due to some out of syallabus qns) is the norm.Prelim papers to me are only beneficial in the sense of stretching one's mind,thinking and understanding of chemistry concepts in greater depth.

      I personally feel today's paper will be a 2/3 mix of straightforward qns seen in past yr q1 to q30 types and also a 1/3 mix of q30-q40 type which are slightly higher in difficulty,to create a paper with moderate difficulty.

       

       

       

      Edited by MapPwner 29 Nov `17, 9:46AM
  • Moderator
    H2 Chemistry @ BedokFunland JC (near VJC & TJC)
    UltimaOnline's Avatar
    14,732 posts since May '05
    • All right MapPwner, it seem slike nobody’s gonna ask any more qns, so I’m gonna leave it in your good hands to post your MCQ answers after today’s Paper 1. I’ll be surprised if you get anything less than 85% score for today’s P1 (if you do, it’ll be indicative of how tough today’s P1 is).

  • do12453's Avatar
    14 posts since Nov '17
    • paper was okay ; although abit weird to have multiple option questions mixed in (the 1 and3, 1,2,3 etc)

       

      however some qns very tricky in my opinion but I did manage 28 which i am quite happy with.

  • MapPwner's Avatar
    145 posts since Aug '15
    • Here are the compiled p1 answers(validated across sources):

      Compiled answers:

      CBDCD

      BBBCB

      AADDA

      BADAC

      AADCD

      AABCA

       

      P1 difficulty was moderate,in line with previous years,albeit some tricky questions as usual.

      Along with my p2,p3,p4 estimates and my p1 score(26/30),my raw overall score is 75.58/100.(There were slight buffers for p2,p3).

      And nevertheless if one looks at the H2 Chemistry Reddit posts,on me claiming that A for A level chem at minimum is 70 and above has generated huge negative feedbacks(a ton of downvotes indicating disagreement) and people of course saying i'm trying to discourage others who didn't do well from posting such stuff,nevertheless even if i didnt said this,doesn't the school internal exam system justifies 70 at minimum to be an A as thats what most schools see it as.

      And oh well,finally A levels is over,even though I didn't do well for all subjects+posted such stuff on estimates which obviously will demoralize anyone(including me by right based on people's comments but I don't feel any discouragement).Hopefully everything turns out well next year for everyone!

       

       

      Edited by MapPwner 29 Nov `17, 6:40PM
  • Moderator
    H2 Chemistry @ BedokFunland JC (near VJC & TJC)
    UltimaOnline's Avatar
    14,732 posts since May '05
    • Originally posted by MapPwner:

      Here are the compiled p1 answers(validated across sources):

      Compiled answers:

      CBDCD

      BBBCB

      AADDA

      BADAC

      AADCD

      AABCA

       

      P1 difficulty was moderate,in line with previous years,albeit some tricky questions as usual.

      Along with my p2,p3,p4 estimates and my p1 score(26/30),my raw overall score is 75.58/100.(There were slight buffers for p2,p3).

      And nevertheless if one looks at the H2 Chemistry Reddit posts,on me claiming that A for A level chem at minimum is 70 and above has generated huge negative feedbacks(a ton of downvotes indicating disagreement) and people of course saying i'm trying to discourage others who didn't do well from posting such stuff,nevertheless even if i didnt said this,doesn't the school internal exam system justifies 70 at minimum to be an A as thats what most schools see it as.

      And oh well,finally A levels is over,even though I didn't do well for all subjects+posted such stuff on estimates which obviously will demoralize anyone(including me by right based on people's comments but I don't feel any discouragement).Hopefully everything turns out well next year for everyone!

       

       


      Thanks for your effort, MapPwner.

      Some people just can't handle the truth, and emotionally take out their inadequacies out on other people. It's called psychological projection.

      Yes indeed, here's wishing a better 2018 for everyone! :)

  • MapPwner's Avatar
    145 posts since Aug '15
    • Hopefully cambridge scans scripts properly haha...

      I remembered for p3 my answers were all over the pages,words and structures drawn very near to the edges of the paper.

  • Moderator
    H2 Chemistry @ BedokFunland JC (near VJC & TJC)
    UltimaOnline's Avatar
    14,732 posts since May '05
  • MapPwner's Avatar
    145 posts since Aug '15
    • Sure sure will upload asap when I'm free.

      1 of the 4 questions i got wrong was pure carelessness.The other 3 was probably a lapse in knowledge i suppose.

      Yep there were tricky questions,such as tertiary bromoalkane qn+Q27,both notorious for having a decent amount of people getting it wrong.

       

      Edited by MapPwner 30 Nov `17, 7:22AM
  • Moderator
    H2 Chemistry @ BedokFunland JC (near VJC & TJC)
    UltimaOnline's Avatar
    14,732 posts since May '05
    • Originally posted by MapPwner:

      Sure sure will upload asap when I'm free.

      1 of the 4 questions i got wrong was pure carelessness.The other 3 was probably a lapse in knowledge i suppose.

      Yep there were tricky questions,such as tertiary bromoalkane qn+Q27,both notorious for having a decent amount of people getting it wrong.

       


      Thanks, MapPwner. I'll leave it to you to choose the most tricky / difficult MCQs, no need entire paper. And take your time, when you free.

  • MapPwner's Avatar
    145 posts since Aug '15
    • The pics are uploaded via this link: https://imgur.com/a/L60Vc

      I just uploaded all the pictures in 1 go as a friend of mine asked for it yesterday and i also saved the pictures so may as well.Questions are not in order.

       

      Edited by MapPwner 30 Nov `17, 7:30AM
  • Moderator
    H2 Chemistry @ BedokFunland JC (near VJC & TJC)
    UltimaOnline's Avatar
    14,732 posts since May '05
    • Originally posted by MapPwner:

      The pics are uploaded via this link: https://imgur.com/a/L60Vc

      I just uploaded all the pictures in 1 go as a friend of mine asked for it yesterday and i also saved the pictures so may as well.Questions are not in order.

       


      Ahhh ok I see it's the entire paper, great thanks! :)

      Any particular set of toughest MCQs to recommend? The ones that most pple got wrong?

  • MapPwner's Avatar
    145 posts since Aug '15
  • Moderator
    H2 Chemistry @ BedokFunland JC (near VJC & TJC)
    UltimaOnline's Avatar
    14,732 posts since May '05
    • Originally posted by MapPwner:

      Notable ones are qn 10,13,27 and 18.


      Ummm unfortunately MCQs 10 & 13 don't seem to be in your image uploads?

  • MapPwner's Avatar
    145 posts since Aug '15
    • Originally posted by UltimaOnline:


      Ummm unfortunately MCQs 10 & 13 don't seem to be in your image uploads?

      pretty sure i uploaded all the mcq questions already so...yeah should have its at the bottom of the page if i'm not wrong on the imgur link.

  • Moderator
    H2 Chemistry @ BedokFunland JC (near VJC & TJC)
    UltimaOnline's Avatar
    14,732 posts since May '05
    • Originally posted by MapPwner:

      pretty sure i uploaded all the mcq questions already so...yeah should have its at the bottom of the page if i'm not wrong on the imgur link.


      Edit : I switch browsers liao. Now can see liao! Sorry for the trouble.

      Edited by UltimaOnline 30 Nov `17, 8:24AM
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