POK OI HOSPITAL TANG PUI KING MEMORIAL COLLEGE
FIRST TERM TEST (1996-1997)
F.5 Chemistry
Class: 5 ____ Date: ----------------------------------
Name: _________________ Time allowed: 60 minutes
Class Number: __________ (P.1-P.3 / 53)
Instructions to students:
1. This paper consists of TWO sections, section A (40%) and section B (60%)
2. Answers ALL questions on the foolscap papers provided.
3. The total score is 100 marks.
____________________________________________________________________________
Section A: Short
Questions (40%)
1. (a) What combustible substances are present in Hong
Kong town gas?
(4 marks)
(b) From
what material is Hong ong town gas made?
(1 mark)
(c) THT is
a smelly substance which is added to town gas. What purpose does it serve?
(1 mark)
(d) Name
another fuel which is used as town gas in other parts of the
world. (1 mark)
2. The alkanes, propane and butane, are commonly sold in
cylinders as LPG.
(a) What
do the initials LPG stand for?
(1 mark)
(b) Name
one use of LPG.
(1 mark)
(c)
Describe one precaution which should be taken when the cylinders are filled with
LPG
(1 mark)
(d) State
the different between LPG and natural gas in
(i)
origin;
(ii)
components.
(4 marks)
3. What three advantages do plastics have over lead for
making toys for children?
(3 marks)
4.
(a) Name the following compounds by IUPAC system.
(4 marks)
(b) Write
the structural formulae for
(4 marks)
(1)
Bromochlorodifluoromethane (BCF)
(2) Butan-2-ol
(3)
2,2-dimethylbutane
(4) 2-bromo-1-chlorobut-1-ene
5.
Burning is an exothermic process.
(a)
Write an equation for the complete combustion of butane.
(2 marks)
(b)
State the three conditions for combustion
(3 marks)
6.
Write an account on ‘particulates--one of the air pollutants’. You
should mention the different types of particulates, the ill-effects on human
beings and the solution methods.
(3
out of 10 marks for this question will be awarded for communication of knowledge
in chemistry using good English)
(10 marks)
Section B: Long questions (60%)
1.
Methane belongs to the homologous series of alkane, a saturated
hydrocarbon. It reacts with chlorine to form chloromethane and hydrogen
chloride.
CH4
(g) + Cl2 ®
CH3Cl (g) + HCl (g)
(a) Give the condition for the above reaction to take place
(1 mark)
(b) What type of reaction is this?
(1 mark)
(c) Explain whether methane or chloromethane has a higher boiling point.
(3 marks)
When
ethane, which belongs to another homologous series, react with chlorine, no
hydrogen chloride is produced.
(d) What is meant by the term homologous series?
(2 marks)
(e) To which homologous series does ethane belong?
(1 mark)
(f) Draw the structural formula of ethane.
(1 mark)
(g) Give the IUPAC name of the reaction product.
(1 mark)
(h) Give the equation for the above reaction.
(1 mark)
(i) What type of reaction is this?
(1 mark)
(j) Suggest a method to distinguish alkene from alkane.
(3 marks)
2.
Mr. Ng, a chemistry teacher, demonstrates an experiment to investigate
the gaseous products of combustion. The apparatus set-up is shown below. The
burning material is placed in the crucible at X and a slow stream of air is
drawn through the apparatus by means of the pump.
(a)
When petrol is burnt at X, the anhydrous copper(II) sulphate turns blue
and the lime water turns cloudy.
(1)
Name the combustion products responsible for these observations.
(2 marks)
(2)
What can be deduced concerning the elements present in petrol?
(1 mark)
(3)
Name a material which would turn the lime water cloudy but would not
affect the anhydrous copper(II) sulphate when it is burnt.
(1 mark)
(4)
Write the equation for the reaction that turns lime water cloudy.
(1 mark)
(5)
Give two different chemical methods by which the cloudiness can be
removed from the lime water, writing equation for the methods you choose.
(4 marks)
(b)
Briefly explain why the combustion of petrol in the engine of the car can
pollute the atmosphere.
(3 marks)
(c)
Using the alkenes as examples, show three characteristics of a homologous
series.
(3 marks)
3.
(I) Below is a flow-diagram showing the cracking of an alkane called
dodecane.
(a) What is an alkane?
(1 mark)
(b) Alkanes are found in crude oil.
(1 mark)
(1) Name the process
used to separate them into usable mixtures.
(2 marks)
(2) Briefly describe
how these mixtures are cracked into more useful substances.
(2 marks)
(c) State an important use for the products of ethane and octane listed
above.
(2
marks)
(II) There are two big classes of plastics, which behave differently when
heated.
(1) Name the two classes.
(2 marks)
(2) Describe their difference in behaviour towards heating.
(2 marks)
(3) How the difference in (2) is related to the molecular structure of
the plastics.
(4
marks)
4.
The diagram below shows how rain becomes acidic.
(a) Name the gas A. How is it produced?
(2 marks)
(b) (1) Gas B contains nitrogen. Name two possible gases for B.
(2 marks)
(2) What is the main
source of these gases?
(1 mark)
(c) Gas C is formed from an impurity in fossil fuels.
(1)
Name the impurity.
(1 mark)
(2) Name gas C.
(1 mark)
(d) What is the approximate pH of:
(1)
unpolluted rain water, and
(2)
acid rain
Give
the reason in each case.
(4 mark)
(e) Reservoirs in Hong Kong are affected by acid rain, State one harmful
effect of acid rain
in reservoir water.
(1 mark)
(f) (1) Name one substance that we can add to the reservoirs to overcome
the problem.
Explain
what it does.
(2 marks)
(2) How does the pH
pf the water change as the water improves?
(1 mark)
(3) Suggest another
way to overcome the problem of acid water in our reservoirs.
(1 mark)
End of Paper