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O Levels Chemistry 2008 Exam Question: Organic Chemistry in Paper 1 (MCQs) – Part 2

In the previous blgopost we have discussed on 3 MCQ questions on Organic Chemistry that came out in 2008 GCE O Levels Chemistry Exams. Let’s continue with the rest of the MCQ questions that are related to Organic Chemistry.

Question 1: under sub-topic “Carboxylic Acids”

The reaction between a carboxylic acid, CxHyCO2H, and an alcohol, CnH2n+1OH, produces an ester.

How many hydrogen atoms does one molecule of the ester contain?

A.? y + 2n
B.? y + 2n + 1
C.? y + 2n + 2
D.? y + 2n + 3

PS: Tricky question that ALL Pure Chemistry students must know how to answer

&

Question 2: under sub-topic “Carboxylic Acids”

The diagram below shows the structure of ethanoic acid, a carboxylic acid.

CH3COOH

How many moles of ethanoic acid react with one mole of magnesium?

A.? 1
B.? 2
C.? 3
D.? 4

&

Question 3: under sub-topic “Alkenes”

The molecular structure of three hydrocarbons are shown below.

Which statement about these hydrocarbons is correct?

A.? All three hydrocarbons are isomers of propene
B.? R is a branched alkene
C.? S is but-1-ene
D.? T is an isomer of butene

PS: Do attempt the questions and leave your answers & suggested reasoning in the ?Leave A Reply? section below

PPS: If you would like more Tips, Notes and Questions on Organic Chemistry, please check out the archives (older blogposts) by CLICKING HERE

Related Articles:

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  • O Levels Chemistry Tips Blog Marathon – Day 3
  • O Level Chemistry: Acids,Bases & Salts / Organic Chemistry
  • O Level Chemistry: Organic Chemistry – Addition Reaction
  • O Levels Chemistry Questions – Organic Chemistry (Carboxylic Acids & Alcohols)

Sean Chua
Sean Chua
Winners Education Centre Pte. Ltd.
Many know me as the Ten Year Series book author for JC A-Level H2 Chemistry and O-Level Pure Chemistry. My 19+ years of coaching experience (since 1999) with more than 1500 students from 180+ JCs and Secondary Schools has allowed me to understand the true reasons why students are not able to perform well in Chemistry. Most importantly, my strength lies in using everyday analogies (even grandmothers can understand!) to simplify abstract concepts. Also, my teaching methodology has been designed to be fun, enjoyable and effective for my students. If you want to have an enjoyable time learning Chemistry and being motivated to excel in Chemistry, contact me today at 98287357

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Comments

  1. C says

    September 28, 2011 at 1:56 am

    for the 3rd question, the answer should be D.
    A and B have been eliminated for the reasons already stated by others earlier.
    As for C,
    S should be but-2-ene if i’m not wrong.
    I’m not very sure so if anyone knows please please correct me! (:

  2. M says

    October 8, 2009 at 4:26 pm

    I think it’s b, b, c? Not too sure about the last though..

  3. daphney says

    October 6, 2009 at 12:06 am

    i agree with TKS that the answers are
    1)B
    2)B
    3)D
    for 2) when balanced the equation of reaction between ethanoic acid and magnesium so we will see that 2 moles of ethanoic acid is reacting with magnesium.
    for 3)D IS THE CORRECT ANS BECAUSE ISOMERS ARE DRAWN BY CHANGING THE POSITION.

    pl z tell if i m wrong or the explanation i have given is wrong.

  4. TKS says

    August 24, 2009 at 5:07 pm

    i think the answer is
    Q1 : B
    Q2 : B
    Q3 : D

    i try to explain how i get my answer, but if i am wrong please quickly tell me, cuz i am no good at this chapter

    Q1 : B is y + 2n + 1

    at first i thought it is y + 2n + 3, but then i forgot that when ester are formed, the hydrogen are taken out from both the carboxylic acid and alcohol, so left with only y + 2n + 1

    Q2 : i think this is just a simple mole calculation question.
    the equation goes like this

    2CH3COOH + Mg ——> (CH3COO)2MG + H2

    therefore, ratio of Mg is to CH3COOH is 1 is to 2,

    and thus the no. of mol of CH3COOH needed to react with one mole of Mg is 2 x 1 = 2mol

    Q3 :

    i do not really know how to do this question, i just guess by eliminating, for option A, it is definitely wrong because that the hydrocarbons has 4 carbon, which is butene.

    option B, R and T are not branched, so option B is out

    Option C, i do not really know wat is means by but-1-ene, but it seems like butene is the only way of saying S. so i decided to choose option D

    also, despite the way my teacher taught me, i still managed to vaguely recognise how isomers look like.. so i think Option D is correct.

    once again, pls tell me if i am wrong in anything thing i tried explaining.

    Cheers
    KS

  5. A0 says

    August 7, 2009 at 12:27 pm

    ans is A??

  6. paul says

    August 2, 2009 at 7:36 pm

    answers pliz

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