Hi Students (and parents),
Thank you for all your email enquries on our annual Organic Chemistry Mastery Workshops 2009 for O Level students.
As mentioned that in 2008 GCE O Levels Chemistry Exams, Organic Chemistry plays a large part of the questions that came out in Paper 1 (Multiple Choice Questions) and 2 (Written).
Today i am going to share with you some of the multiple choice questions that came out. I will help you by directing you to the “sub-topics” of Organic Chemistry that the question is based on:
Question 1: Under sub-topic ” Fuels”
In how many of the following can paraffin (kerosene) be used as the energy source?
Aircraft, Air Conditioning Units, Cars, Domestic Cooking, Heavy Lorries, Power Stations
A) 1
B) 2
C) 3
D) 4
&
Question 2: under sub-topic “Alkanes”
Which statements are true of alkanes?
1. Their general formulae is CnH2n
2. They are flammable
3. They react with chlorineA) 1 and 2 only
B) 2 and 3 only
C) 1 and 3 only
D) 1, 2 and 3
&
Question 3: under sub-topic “Alkenes”
Two gases, X and Y, have the following properties.
1. X dissolves in aqueous sodium hydroxide but Y is insoluble
2. Y burns in excess oxygen to give X and water only
3. Y does not decolourise aqueous bromineWhat are gases X and Y respectively?
A) Carbon monoxide and ethene
B) Carbon monoxide and ethane
C) Carbon dioxide and ethene
D) Carbon dioxide and ethane
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
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- O Levels Chemistry – Selected Exam Questions
- O Levels Chemistry 2008 Exam Question: Organic Chemistry in Paper 1 (MCQs)-Cont’d
- O Level Chemistry: Organic Chemistry – Addition Reaction
Q1) Answer is B
cos usage of paraffin is for only cooking and aircrafts
Heavy Lorry should probably use diesel and cars use petrol.
Q2) Answer is B
Option 1 is of course wrong cos formula for alkane is CnH2n+1
Option 3 is correct cos alkane undergo substitution rxn.
Option 2 must be correct cos by elimnation
Q3) Answer is D
Y does not decolorise aq bromine, means that it is a saturated hydrocarbon and not alkene.
So definitely, options B/D is the answer. I believe that carbon dioxide is produced in excess oxygen and combustion occurs.
Therefore, its D.
Carbon dioxide
Reply
Winston C Reply:
July 14th, 2009 at 6:59 pm
Yah, sorry about the error
Reply
sean Reply:
September 8th, 2009 at 10:32 pm
Glad you learning from your mistakes!
Review and revise towards excellence!
cheers
Sean
Reply
All Answers are correct, but one of the explanations are wrong. Alkanes have a general formula of CnH2n+2, not +1
Reply
sean Reply:
September 8th, 2009 at 10:31 pm
Well Done Jun Wei and Winston!
Glad you are taking actions!
To Your Academic Success in Chemistry,
Sean
Reply
[...] 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 [...]
Huh??? Formula for alkanes is C2H2n+2. Lols.
Reply
sean Reply:
October 15th, 2009 at 12:29 pm
Hi James,
General Molecular Formula for Alkanes Homologous Series is CnH2n+2.
Hope this information helps. =)
To Your Academic Success in Chemistry,
Sean Chua
Reply
i think the answer is c which is 3 cause only air condition units,domestic cooking and power stations use kerosene
Reply
sean Reply:
October 15th, 2009 at 12:44 pm
Hi Garcia,
Where are you from?
In domestic cooking and power stations, we do not generally use kerosene if other suitable choices of fuel are present.
Hope this information helps. =)
To Your Academic Success in Chemistry,
Sean Chua
Reply
my answer are ,B,B and D because th third question bromine decolorised only in
saturated hydro carbons A and C are not saturated they are unsaturated and the
answer will be from B and D my answer is D because in combustin
Reply
Hi Mr Chua!
Ans 1: A
I don’t get it, why is the answer B? I thought natural gases are used in cooking, not kerosene ?? *confused.
Ans 2: B
Ans 3: D
Thanks!!
Reply
Question 1:Ans. A,Kerosene is used only for cooking purpose as it is crude and other applications make use of fractionally seperated paraffins with range of calorific values.
Question 2:Ans. B, Alkanes belong to the general formula CnH2n+2,They are non polar so have low boiling point as a resul they are inflammable;And they show substitution reaction by chlorine eitherr by radicle or carboniyum ion as an intermediate.
Question 3:Ans D;Carbon dioxide dissolves in sodium hydroxide to give sodium bicarbonate and as ethane is saturated hydrocarbon it does not show any substitution reaction with bromine also it can be oxidise to carbondixide and methane with the liberation of hydrogen.
Reply