Comments on: O Levels Chemistry 2008 Exam Question: Organic Chemistry in Paper 1 (MCQs)-Cont’d

By: C

Tue, 27 Sep 2011 17:56:42 +0000

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! (:

By: M

Thu, 08 Oct 2009 08:26:37 +0000

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

By: daphney

daphney — Mon, 05 Oct 2009 16:06:30 +0000

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.

By: TKS

TKS — Mon, 24 Aug 2009 09:07:18 +0000

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

By: A0

A0 — Fri, 07 Aug 2009 04:27:11 +0000

ans is A??