POK OI HOSPITAL TANG PUI KING MEMORIAL COLLEGE
FIRST TERM TEST (1996-1997)
F.7 Chemistry
Class: 7 ____ Date:
Name: _________________ Time allowed: 90 minutes
Class Number: __________ (P.1-P.4 / 20)
Instructions to students:
1. There are TWO sections in this paper, section A and section B
2. Answers ALL questions of Section A in the space provided in this Question/Answer Book.
3. Section A carries 32 marks and Section B carries 68 marks.
4. The total score is 100 marks.
____________________________________________________________________________
Section A: Short
Questions (32%)
1. Write a structural formula for each of the following
compounds:
(@ 1 mark)
a) 3-methylbutan-2-one
b) 4-nitrobenzaldehyde
c) 2) phenylbut-2-ene
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---------------------------
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d) Benzoyl chloride
e) hex-4-en-2-ol
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2. Give the IUPAC name for each of the following
compounds
(@ 1 mark)
3. What do you understand by the term ‘condensation
reaction’ ? Illustrate your answer with reference to carbonyl compounds.
(5 marks)
4.
write all steps for the preparation of (CH3)3CCONH2
from (CH3)3CCOOH.
You
should write down all reagents required for each step.
(3 marks)
5.
Three unlabelled bottles contain propanal, propanone and heptane. What
tests could you use to aid in labelling the bottles?
(6 marks)
6.
Arrange the following amines in order of increasing basicity and explain
your arrangement.
(8 marks)
Section B: Long Questions (68 marks)
1.
(a) Give three tests to distinguish between an alcohol and a phenol. For
each test, state clearly how the test distinguishes the phenol from the alcohol.
(6 marks)
(b)
5 cm3 of ethyl benzoate are mixed with 30 cm3 of 2 M
sodium hydroxide solution and heated under reflux for about 15 minutes, until
all the oily drops have disappeared. The flask is then fitted for fractional
distillation and the mixture is distilled until the boiling point reaches 78oC
to give a distillate A. The contents of the flask are allowed to cool and then
slowly acidified with concentrated hydrochloric acid, a precipitate of B
separates. This precipitate is purified by recrystallization from water.
(i)
Give one chemical test to identify the liquid A.
(4 marks)
(ii)
(1) What is the precipitate B?
(2 marks)
(2) Write an equation for its formation.
(2 marks)
(iii)
(1) Describe how you would separate and recrystallize the precipitate B.
(3 marks)
(3 marks)
(c)
Offer explanation to the following statements:
(i)
Iodoalkanes are often use in organic chemistry in preference to the
corresponding bromo- or chloro- compounds.
(2 marks)
(ii) Non-strick frying pans are coated with an organic fluoro-compound,
polytetrafluoroethene
while there is little risk of food contamination by the fluorine.
(2 marks)
(iii) The apparent inertness of chlorobenzene to hydrolysis is due to the
interaction of
lone
pair of electron of the chlorine atom with the electron system of the benzene
ring
(3 marks)
(iv) The addition of aqueous sodium hydroxide solution increases the
yield of ethanol
in the reaction
C2H5Cl + H2O ®
C2H5OH + HCl
(2 marks)
(v) The C-O-H bond angle in methanol (109o) is greater than
the H-O-H bond angle in
water(104.5o)
(3 marks)
(vi) Even though phenol, C6H5OH, has a hydroxyl
group, it is only partially soluble in
water.
(2 marks)
2.
(a) The organic compound X, which contains carbon, hydrogen and oxygen
only, was found to have a relative molecular mass of about 85. When 0.43g of X
is burnt in excess oxygen, 1.10g of carbon dioxide and 0.45g if water are
formed.
(i)
What is the molecular formular of X?
(6 marks)
(ii)
Write all possible non-cyclic structures of X.
(7 marks)
(iii) X undergoes a condensation with hydroxylamine and 2, 4-dinitrophenylhydrazine. X also produces
a
yellow precipitate with a mixture of iodine and alkali.
(1) What are the names of the possible structures of X which give positive
results for tests in
(iii)
(2 marks)
(2)
How to distinguish the isomers in (1) if they are separately places in
unlabelled bottles?
(3 marks)
(3)
Write an equation for the reaction of one of the possible structions of
compound X in (1) with
(I) hydroxylamine,
(2 marks)
(II)
a mixture of iodine and sodium hydroxide.
(2 marks)
(b) The following sequence shows a method of preparing cyclohexene from
cyclohexane.
(i)
Suggest the reagent(s) and condition(s) for carrying out each pf the
steps (1) to (3) on a laboratory scale.
(3 marks)
(ii)
Suggest mechanisms for each step.
(9 marks)
End
of Paper