Close
Close

Login here to access/preview our exam papers, or sign up now for your free membership!



2011
Mon
14
Nov
Little Miss Loi avatar

GCE O Level 2011 Oct/Nov Chemistry 5072 (MCQ) Paper 1 Suggested Answers & Solutions

(102)
Tuition given in the topic of Little Miss Loi the Science Tutor (archived) from the desk of Little Miss Loi at 9:23 am (Singapore time)

Another morning, another booklet, another series of codes sent:

Q1-10CDDAA CBDBA
Q11-20BABDA DAADB
Q21-30BADBD ADDDA
Q31-40CDBCB ABCCA

Note: After staring long and hard at the ang moh anomaly that is Q22, I’ve decided to change its answer to A. Reason being that scrap steel, containing a higher percentage (98%) of iron, will lead to a better yield and reduce mining wastes when iron is produced from it via recycling. The highlighted portion would definitely qualify as a correct reason if only it had been included in the original statement – instead of sparking intense debates like this 🙁

Do they tally with yours?

Update: Once again, the list of workings and explanations for each of the answers (where applicable) have been compiled (along with the questions at the end)!

You may access here by clicking the Like button (if you haven’t yet done so).

GCE O Level 2011 Chemistry 5072 Paper 1 solutions

2011 O-Level October/November Chemistry 5072 Paper 1 Suggested Solutions

As usual, hopefully this will help in some way to settle some of the debates regarding some of the answers (and hopefully not create more in the process!)

頑張って!!!

Revision Exercise

To show that you have understood what Miss Loi just taught you from the centre, you must:

  1. Leave A Comment!
Comments & Reactions

87 Comments

  1. Lucius's Avatar
    Lucius commented in tuition class


    2011
    Nov
    14
    Mon
    9:37am
     
    1

    Could you explain question 8, 22, 24 and 28? Lol

  2. Gary Lee's Avatar
    Gary Lee commented in tuition class


    2011
    Nov
    14
    Mon
    9:39am
     
    2

    35/40... Is that bad?
    Can you kindly explain 9,22 and 35? Thanks!
    Cheers!

  3. Dannie's Avatar
    Dannie commented in tuition class


    2011
    Nov
    14
    Mon
    9:58am
     
    3

    dont agree with qn8; heres my working:
    % of C= 72/222 x 100=32.4%
    % of H = 18/222 x 100=8.1%
    % of Si= 84/222 x 100=37.8%
    % of O=48/222 x 100=21.6%
    thus, Si has highest % by mass.
    so answer should be D rite?

  4. April Nguyen's Avatar
    April Nguyen commented in tuition class


    2011
    Nov
    14
    Mon
    10:05am
     
    4

    I think the answer for question 3 is B...I mean, ammonium salts are heated with alkalis will give off amonium gas, isnt it right?

    • anonymous's Avatar
      anonymous replied to April Nguyen’s comment


      2011
      Nov
      14
      Mon
      10:45am
       
      4.1

      @April Nguyen: April Nguyen

      question 3 should be D. This is because the question said that ammonia is "only" given off after aluminium foil is added to the hot solution. If the aqueous salt was ammonium nitrate, ammonia gas would have been given off the moment sodium hydroxide was added to it. ( This is QA). Thus, it can be seen that the aqeous salt has nitrate as it gives off ammonia when aluminium foil is added but cannot be ammonium nitrate because ammonia would already have been given off when sodium hydroxide was added. Hence, the only other possible nitrate would be sodium nitrate.

  5. April Nguyen's Avatar
    April Nguyen commented in tuition class


    2011
    Nov
    14
    Mon
    10:14am
     
    5

    and isnt the answer for 17 is D? I mean, sure, metals from Group I have decreasing melting point down the group but not all alkali metals are from Group I?

  6. anonymous's Avatar
    anonymous commented in tuition class


    2011
    Nov
    14
    Mon
    10:29am
     
    6

    my mark is 38/40 this time round but i think i might be in danger because alot of people found the paper quite easy. could you explain question 22 on the iron and steel thing. why is the answer not A? option 2 seems quite relevant. scrap steel does have a higher percentage of iron than iron ore and hence it has to be recycled to so call "conserve the iron" or something? can explain? thanks!

  7. shivaanand's Avatar
    shivaanand commented in tuition class


    2011
    Nov
    14
    Mon
    10:38am
  8. Goh Rui Yi's Avatar
    Goh Rui Yi commented in tuition class


    2011
    Nov
    14
    Mon
    10:44am
  9. Anonymous's Avatar
    Anonymous commented in tuition class


    2011
    Nov
    14
    Mon
    10:57am
     
    9

    Can someone please explain qn 22 35 and 37? Shouldn't 37 be D?

  10. 2's Avatar
    2 commented in tuition class


    2011
    Nov
    14
    Mon
    11:01am
     
    10

    Hi can you explain q3,5,12,22? For q3 why is it not ammonium nitrate since ammonia is given off? For q5 shouldn't the electrons become lesser cuz electrons are used to carry charges? For q12 why is it a and not c? They intersect at a point for volume of gas doesn't mean they are same rate isnt it? Doesnt rate refer to the gradient of volume time graph? For q22 I chose d as I thought recycling would not produce less co2 as the co2 produced is due to the reaction of coke with oxygen and not the purity of iron. Thank you!

  11. Anonymous's Avatar
    Anonymous commented in tuition class


    2011
    Nov
    14
    Mon
    11:05am
  12. LM's Avatar
    LM commented in tuition class


    2011
    Nov
    14
    Mon
    11:06am
     
    12

    can u estimate the belll curve tis time for a1?

  13. X.'s Avatar
    X. commented in tuition class


    2011
    Nov
    14
    Mon
    11:11am
     
    13

    yea can someone pls explain Qn 22,
    I put my ans as 1,2,3 (option A) I know 1 and 3 is correct cos it's in the TB , but im not sure about 2!

    um can someone explain qn 35 too? i put option a too :O

    i know for qn 37, the ans is B cos since the number of carbon atoms increases, its harder to burn THUS less flamable. it becomes more viscous as number of carbon atoms increase! so D is wrong.

  14. unknown's Avatar
    unknown commented in tuition class


    2011
    Nov
    14
    Mon
    11:12am
     
    14

    why qn4 ans is not B? and qn19, why is th ans not B?

  15. X.'s Avatar
    X. commented in tuition class


    2011
    Nov
    14
    Mon
    11:13am
     
    15

    i hope i can get a1, had 38/40 for this mcq but im not rly confident for paper 2. found this years papers harder than last years ones 🙁 quite a few weird qns i never see before! the qn 22 esp.
    depending on chem + bio . my physics cmi one hahahah

  16. 2's Avatar
    2 commented in tuition class


    2011
    Nov
    14
    Mon
    11:15am
     
    16

    Hi can you explain q5,12,22? For q5 shouldn't the electrons become lesser cuz electrons are used to carry charges? For q12 why is it a and not c? They intersect at a point for volume of gas doesn't mean they are same rate isnt it? Doesnt rate refer to the gradient of volume time graph? For q22 I chose d as I thought recycling would not produce less co2 as the co2 produced is due to the reaction of coke with oxygen and not the purity of iron. Thank you ^^

    • X.'s Avatar
      X. replied to 2’s comment


      2011
      Nov
      14
      Mon
      12:19pm
       
      16.1

      @2: according to my friend,
      for qn 5, ans is A cos number of electrons must match the protons! and it doesnt become lesser over time. im not sure if this is the right explanation but i also put my ans as A.
      for qn 12 i know its A definitely becos i did that qn so many times in exam papers.... they are at different rates cos exp 1 has a steeper gradient than exp 2! different rates of reaction but same vol of gas produced. so exp 1 takes less time for the reaction to end.

    • SQhi's Avatar
      SQhi replied to 2’s comment


      2011
      Nov
      14
      Mon
      1:22pm
       
      16.2

      @2: Q5

      The incoming electrons from one end of the metal displaces electrons at the other end of the metal, period.

      Q12 excellent explanation by X. above

      Q 22 my opinion is A(deviation from miss loi)

      1. The blast furnace process produces a lot of CO2 as CO is used to reduce hematite, and a lot of heat is needed, fuel burnt = more CO2. Iron products already have a high percentage of iron, such as steel, see no. 2

      2. Scrap steel does contain a higher percentage of iron than iron ore, iron ore is mostly earth!

      3 is always right.

  17. unknown's Avatar
    unknown commented in tuition class


    2011
    Nov
    14
    Mon
    11:33am
  18. 린젠레's Avatar
    린젠레  commented in tuition class


    2011
    Nov
    14
    Mon
    11:33am
     
    18

    Hi! May i ask whether for question 39, can the answer be A?

  19. Daniel's Avatar
    Daniel commented in tuition class


    2011
    Nov
    14
    Mon
    11:33am
     
    19

    Hey can i ask out of curiosity why is qs 22 the part about scrap steel having a higher percentage of iron is not a reason?

  20. W's Avatar
    commented in tuition class


    2011
    Nov
    14
    Mon
    11:36am
     
    20

    Can you explain why the ans. for 22 and 35 isn't A?

  21. 린젠레's Avatar
    린젠레  commented in tuition class


    2011
    Nov
    14
    Mon
    11:43am
     
    21

    @Daniel & W: For Qn 22, if you go and calculate the mass percentage of iron in Fe2O3, you'll realise that the % is higher than the 40% that is contained in scrap metal.

  22. NY's Avatar
    NY commented in tuition class


    2011
    Nov
    14
    Mon
    12:08pm
  23. Alissya's Avatar
    Alissya commented in tuition class


    2011
    Nov
    14
    Mon
    12:11pm
     
    23

    Hi may i ask why question 28 is D? can it be A since they asked for fossil fuels? CO(carbon monoxide) is from incomplete combustion of fuels that contain carbon i thought? and the SO2 was from incomplete combustion of fossil fuels/ volcanic eruptions?

  24. Joseph's Avatar
    Joseph commented in tuition class


    2011
    Nov
    14
    Mon
    12:18pm
     
    24

    Hi, isnt question 22 answer be A instead of C? Because Steel contains 98% iron and 2% carbon?

  25. XOXO's Avatar
    XOXO commented in tuition class


    2011
    Nov
    14
    Mon
    12:34pm
     
    25

    hello:)
    can someone pls explain Q28
    cause i thought that C8H18 (octane) is a liquid and not a GAS resulting in incomplete combustion?
    so why is the answer D?
    and can it be B? lols
    pls and thankyou:)

  26. Elaine's Avatar
    Elaine commented in tuition class


    2011
    Nov
    14
    Mon
    12:44pm
     
    26

    Can someone upload the question paper? Cos our school haven return our question paper ...

  27. crapper's Avatar
    crapper commented in tuition class


    2011
    Nov
    14
    Mon
    1:57pm
     
    27

    shouldn't question 9 be option D?
    Shouldn't question 19 be option A? (how could the last element in the period -noble gas have an increase in valency electron?)

  28. Dannie's Avatar
    Dannie commented in tuition class


    2011
    Nov
    14
    Mon
    2:51pm
     
    28

    i think i ald lost 1-2 marks: qn 5,35
    paper 2 was ok but im afraid i might lose marks esp becos i did the organic chem qn, the calculations part
    hopefully can get A1/A2:)

  29. marc's Avatar
    marc commented in tuition class


    2011
    Nov
    14
    Mon
    3:46pm
     
    29

    can miss loi post the full soln ans, + qn pp just like physics, thanks very much.

  30. hk's Avatar
    hk commented in tuition class


    2011
    Nov
    14
    Mon
    5:26pm
     
    30

    erm anyone has combine biology answer for the mcq link?

  31. ces's Avatar
    ces  commented in tuition class


    2011
    Nov
    15
    Tue
    4:14pm
  32. skylar's Avatar
    skylar commented in tuition class


    2011
    Nov
    15
    Tue
    11:02pm
     
    32

    Qns 5 , very disputed. Some say A some say D. Can someone explain to me with a solid answer ? thanks in advance.



    • 2011
      Nov
      17
      Thu
      8:48pm
       
      32.1

      @skylar: I believe those who chose D are looking only at the positive ions and electrons on the original diagram that have subsequently flowed to one side of the metal.

      While the number of electrons in the metal remains constant due to the conservation of mass, the metal being part of a closed circuit will have more electrons coming from the circuit to take the place of those who have flowed on from one side to another, so the electrons cannot be permanently held at one end only.

      Furthermore with the current switched off, the arrangement of the electronics should return to what it was like before the current was switched on i.e. the original diagram!

  33. Little Miss Loi's Avatar
    Little Miss Loi commented in tuition class


    2011
    Nov
    17
    Thu
    9:41pm
     
    33

    Folks, after staring long and hard at the ang moh anomaly that is Q22, I’ve decided to change its answer to A. Reason being that scrap steel, containing a higher percentage (98%) of iron, will lead to a better yield and reduce mining wastes when iron is produced from it via recycling.

    The highlighted portion would definitely confirm chop stamp qualify as a correct reason if only it had been included in the original statement – instead of sparking intense debates all over SIngapore 🙁

15 Reactions

  1. Tweetback
    Shaojie tweeted


    2011
    Nov
    14
    Mon
    1:43am
     
    34

    Tally your Chemistry MCQ answers here? http://t.co/Zvs1LxKb #chemistry #olevel



  2. 2011
    Nov
    14
    Mon
    1:53am
  3. Tweetback
    Tania Chang tweeted


    2011
    Nov
    14
    Mon
    3:07am
     
    36

    @chickennuhget RT @MissLoi: Tally your Chemistry MCQ answers here? http://t.co/Rp1LESUx #olevel

  4. Tweetback
    SYR tweeted


    2011
    Nov
    14
    Mon
    3:49am
     
    37

    RT @MissLoi: Tally your Chemistry MCQ answers here? http://t.co/5vkFNTpT #olevel



  5. 2011
    Nov
    14
    Mon
    3:56am
  6. Tweetback
    WanLing tweeted


    2011
    Nov
    14
    Mon
    4:08am
  7. Tweetback
    Quah Xiao Xi tweeted


    2011
    Nov
    14
    Mon
    4:37am
  8. Tweetback
    Valarie ∞ tweeted


    2011
    Nov
    14
    Mon
    5:21am
  9. Tweetback
    FUNGLING  tweeted


    2011
    Nov
    14
    Mon
    5:27am
  10. Tweetback
    Min Hui tweeted


    2011
    Nov
    14
    Mon
    5:40am
  11. Tweetback
    Michael Mick tweeted


    2011
    Nov
    14
    Mon
    9:46am


  12. 2011
    Nov
    14
    Mon
    12:20pm
  13. Tweetback
    Wei Tai tweeted


    2011
    Nov
    14
    Mon
    1:03pm
  14. Tweetback
    Kar Mei tweeted


    2011
    Nov
    14
    Mon
    1:50pm
  15. Tweetback
    Kar Mei tweeted


    2011
    Nov
    14
    Mon
    1:50pm

Post a Comment

  • * Required field
  • Your email will never, ever be published nor shared with a Nigerian banker or a pharmaceutical company.
  • Spam filter in operation.
    DO NOT re-submit if your comment doesn't appear.
  • Spammers often suffer terrible fates.
*
*

Impress Miss Loi with beautiful mathematical equations in your comment by enclosing them within alluring \LaTeX [tex][/tex] tags (syntax guide | online editor), or the older [pmath][/pmath] tags (syntax guide). Please PREVIEW your equations before posting!

CommentLuv badge
 

 

Whatsapp Instagram Twitter Facebook Close Search Login Access RSS Joss Sticks Sessions Suggested Solutions Preview O Level Additional Mathematics O Level Elementary Mathematics Secondary Three Additional Mathematics Secondary Three Elementary Mathematics Secondary Two Mathematics Secondary One Mathematics Additional Mathematics 4038 Additional Mathematics 4018 Elementary Mathematics 4017 Virus Zoom