Secondary School Mathematics & Science Competition 2016
Chemistry
Date
: 1 May, 2016
Time allowed : 12:00 - 1:15 pm (1hour 15 minutes)
1.
Total no. of pages : 14 (excluding the current page)
Total marks
: 60
Write the Candidate Number, Exam Centre Number, Seat Number, Name in English, Name of School, Form,
Language and Subject in the spaces provided on the Part A MC Answer Sheet and the Part B Answer Sheet.
2.
When told to open this question paper, the candidate should check that all the questions are there. Look
for the words ‘END OF PAPER’ after the last question.
3.
Answer ALL questions in Part A.
a.
The candidate is advised to use an HB pencil to mark all answers on the MC Answer Sheet.
b.
Each question carries one mark.
c.
The candidate should mark only ONE answer for each question. If the candidate marks more
than one answer, his/her will receive NO MARK for that question.
4.
There are SIX questions in Part B. Answer ANY FIVE questions. Answers should be written in the space
provided on the Part B Answer Sheet.
5.
A Periodic Table is provided on the last page of the question paper.
6.
No mark will be deducted for wrong answers.
7.
The diagrams in this paper are not necessarily drawn to scale.
© The Hong Kong Polytechnic University 2016 All Rights Reserved.
Part A: Multiple Choice Questions (40%)
Which of the following shows the correct order of the melting points of the metals?
A)
B)
C)
D)
Sodium > Magnesium > Aluminium > Potassium
Aluminium > Magnesium > Sodium > Potassium
Magnesium > Sodium > Potassium > Aluminium
Potassium > Sodium > Magnesium > Aluminium
With the following set-up, town gas was passed over a powdered copper(II) oxide. Liquid X was
collected.
Liquid X would
A)
B)
C)
D)
neutralize sulphuric acid.
turn hydrogencarbonate indicator purple.
turn red litmus paper blue gradually.
turn anhydrous cobalt(II) chloride paper pink.
Which of the following operation will NOT bring about chemical reactions?
A)
B)
C)
D)
Adding sodium granules to potassium nitrate solution
Adding a copper strip to concentrated hydrochloric acid
Adding a magnesium ribbon to copper(II) nitrate solution
Immersing a silver ring into concentrated sulphuric acid
The following substances were burnt in oxygen and the products were mixed with water. Which one of
them would produce a resulting aqueous solution with the highest pH value?
A)
B)
C)
D)
Calcium
Iron
Sulphur
Carbon
1
Metal X gives out some colourless gas bubbles when it is put into dilute sulphuric acid. Which of the
following about metal X MUST BE CORRECT?
A)
B)
C)
D)
Metal X gives out a colourless gas when it is put into water.
Heating the oxide of metal X can give out a gas which can relight a glowing splint.
Silvery solid is formed when metal X is put into silver nitrate solution.
Metal X can be extracted by heating the oxide of metal X with carbon.
Four set-ups are shown below. Arrange the rates of rusting of the four iron nails in an ascending order.
(I)
(II)
anhydrous
calcium chloride
cotton wool
sea water
iron nail
iron nail
(III)
(IV)
oil layer
distilled water
boiled distilled water
iron nail
A)
B)
C)
D)
iron nail
(III) < (II) < (IV) < (I)
(IV) < (I) < (III) < (II)
(II) < (IV) < (I) < (III)
(II) < (III) < (I) < (IV)
Refer to the following reversible reaction performed at constant pressure.
CH4(g) + H2O(g)
CO(g) + 3H2(g)
H = +206 kJ mol–1
Which of the following statements are CORRECT when the temperature increases?
(I) The volume of the system increases.
(II) The rates of backward reaction increases.
(III) The backward reaction is endothermic.
A)
B)
C)
D)
(I) and (III) only
(I) and (II) only
(II) and (III) only
All of the above
2
The two graphs below represent a gaseous reversible system at different temperature and pressure.
Which of the following statement(s) is/are CORRECT?
(I) The forward reaction is exothermic.
(II) The increase in the volume of the container would lead to a higher product yield.
(III) The rate of the backward reaction increases to a larger extent when catalyst is added to the system.
A)
B)
C)
D)
(I) only
(II) only
(I) and (III) only
(II) and (III) only
All isotopes of tin have the same
(I) number of electrons.
(II) number of protons.
(III) number of neutrons.
A)
B)
C)
D)
(I) only
(II) only
(I) and (II) only
(II) and (III) only
An element with symbol Y has the electronic arrangement of 2,8,6. Which of the following species
would Y most likely form?
A)
B)
C)
D)
YO4
Y 4O
YF6
Y 6F
3
The formula for molybdenum (III) nitrate is
A)
B)
C)
D)
MoNO3
Mo(NO3)3
Mo2NO3
Mo3NO3
Which of the following reactions between an alkali metal and a halogen is the most vigorous?
A)
B)
C)
D)
Potassium reacting with chlorine
Potassium reacting with bromine
Sodium reacting with chlorine
Lithium reacting with bromine
A certain sample of element Y contains 60 % of
mass of element Y in this sample?
A)
B)
C)
D)
69
Y and 40 % of
71
Y . What is the relative atomic
69.2
69.8
70.0
70.2
Which of the following substances has the lowest electrical conductivity?
A)
B)
C)
D)
Cu(s)
Hg(l)
H2(g)
LiOH(aq)
Down the group, the electronegativity of the elements
A)
B)
C)
D)
decreases because the atomic number increases.
decreases because the atomic size increases.
increases because the number of energy levels increases.
increases because the atomic number increases.
Which of the following molecules is non-polar, but containing polar bonds?
A)
B)
C)
D)
PCl5
H2O
SO2
NH3
4
Bromine has a higher boiling point than chlorine because it has a higher
A)
B)
C)
D)
reactivity.
bond enthalpy.
bond polarity.
molecular mass.
Why the boiling point of NH3 is higher than PH3?
A)
B)
C)
D)
NH3 is polar where PH3 is non-polar.
NH3 is bound by intermolecular hydrogen bond where PH3 is not.
Van der Waals’ forces are stronger in NH3 than in PH3.
The molar mass of NH3 is lower than that of PH3.
Which of the following correctly describes the sequence of procedures to separate sand, salt and water
from a mixture of sand and salt solution?
A)
B)
C)
D)
Filtration, evaporation
Filtration, distillation
Crystallization, filtration
Crystallization, filtration, distillation
Which of the following components of air is NOT obtained industrially from fractional distillation of
liquid air?
A)
B)
C)
D)
Ar(g)
CO2(g)
N2(g)
O2(g)
Which of the following substances has a sharp boiling point?
A)
B)
C)
D)
Cola drink
Sugar solution
Distilled water
Liquid air
Which of the following is NOT a chemical change?
A)
B)
C)
D)
A piece of carbon burns.
A cake is baked in an oven.
Sublimation of Iodine.
Calcium is put in water.
5
The enthalpy changes of three reactions under certain conditions are shown below:
Reaction
Standard enthalpy change (ΔH)
2NO(g) + O2(g)  2NO2(g)
–116 kJ mol–1
2N2(g) + 5O2(g) + 2H2O(l)  4HNO3(aq)
–256 kJ mol–1
N2(g) + O2(g)  2NO(g)
+183 kJ mol–1
Using the above data, determine the enthalpy change for the following reaction:
3NO2(g) + H2O(l)  2HNO3(aq) + NO(g)
A)
B)
C)
D)
37.3 kJ mol–1
229 kJ mol–1
137 kJ mol–1
485 kJ mol–1
Three samples of zinc granules (1 g each) are added to three samples of excess dilute hydrochloric acid
at 20oC, 25oC and 30oC respectively. Which of the following sets of curves represent the correct plots of
the volume of gas produced against time?
How many cis-trans isomer(s) does CH2=CCH3CH=CH2 have?
A)
B)
C)
D)
0
1
2
3
6
What is the systematic name of the following compound?
A)
B)
C)
D)
1,3-dibromobut-2-ene
2,4-dibromobut-2-ene
1,3-dibromo-1-methylpropene
1,3-dibromo-3-methylpropene
Which of the following diagrams is produced by the titration of a weak base against a strong acid?
12
A.
12
B.
8
8
pH
pH
4
4
Volume of titrant
Volume of titrant
12
C.
12
D.
8
8
pH
pH
4
4
Volume of titrant
Volume of titrant
Four aqueous solutions, I, II, III and IV, are listed below.
(I)
(II)
(III)
(IV)
0.1000 mol dm-3 HCl
0.0100 mol dm-3 HCl
0.1000 mol dm-3 NaOH
0.0100 mol dm-3 NaOH
Arrange the above solutions in ascending pH values.
A)
B)
C)
D)
(I) < (II) < (III) < (IV)
(I) < (II) < (IV) < (III)
(II) < (I) < (III) < (IV)
(II) < (I) < (IV) < (III)
7
Sodium chromate, Na2CrO4, dissolves in water to give a yellow solution. When dilute hydrochloric acid
is added to the solution, the following reaction occurs:
2CrO42(aq) + 2H+(aq)  Cr2O72(aq) + H2O(l).
Which of the following statements concerning this reaction is CORRECT?
A)
B)
C)
D)
The colour of the solution changes from yellow to green.
Chromate ions act as a reducing agent.
The oxidation number of chromium remains unchanged during the reaction.
The reaction is a neutralization reaction.
The reaction of cane sugar and concentrated sulphuric acid may be represented by the following
equation:
In this reaction, concentrated sulphuric acid acts as
A)
B)
C)
D)
a dehydrating agent.
an oxidizing agent.
a drying agent.
a strong acid.
In an experiment to determine the concentration of sulphuric acid in a brand of toilet cleaner, 25.0 cm3
of the cleaner was first diluted to 250.0 cm3 with distilled water. Upon titration with 0.680 M sodium
hydroxide solution using phenolphthalein as indicator, 25.0 cm3 of the diluted cleaner required
23.2 cm3 of the sodium hydroxide solution to reach the end point.
What is the concentration of sulphuric acid in the undiluted toilet cleaner?
A)
B)
C)
D)
0.32 M
0.63 M
3.16 M
6.31 M
Which of the following reactions does nitrogen undergo oxidation?
A)
B)
C)
D)
NO2  N2O4
NO3-  NO2
N2O5 NO3NH3  N2
8
Consider the following set-up:
Electrons flow from Electrode X to Y in the external circuit. Which of the following combinations is
CORRECT?
A)
B)
C)
D)
Electrode X
carbon
zinc
carbon
zinc
Electrode Y
silver
magnesium
carbon
carbon
Solution Z
silver nitrate solution
magnesium sulphate solution
copper(II) sulphate solution
silver nitrate solution
Both X and Z are metals. X reacts with Z(NO3)2 solution according to the following equation:
X(s) + Z2+(aq)  X2+(aq) + Z(s)
Metals X and Z are used as the electrodes in a chemical cell with sodium chloride solution as electrolyte.
Which of the following statements about the chemical cell are CORRECT?
(I) Metal X acts as the anode.
(II) Metal Z acts as the positive electrode.
(III) Electrons flow from metal Z to metal X in the external circuit.
A)
B)
C)
D)
(I) and (III) only
(I) and (II) only
(II) and (III) only
All of the above
9
A fork which is made of metal M can be silver-plated by the set-up shown below:
When a current passed through the solution for 10 min, which of the following would occur?
(I)
(II)
(III)
(IV)
A)
B)
C)
D)
Silver ions would migrate to the silver electrode.
Silver ions would be reduced at the cathode.
The metal M would go into solution as ions.
The mass of the fork would increase.
(I) and (III) only
(I) and (IV) only
(II) and (III) only
(II) and (IV) only
Which of the following statements is the CORRECT description of period II elements?
A)
B)
C)
D)
They have 2 electrons in their outermost electron shells.
They have similar melting point.
The atomic size becomes smaller across the period.
They have similar chemical properties.
A gaseous alkane and a gaseous alkene are treated separately in the following ways. Which of the
following treatments can distinguish between C4H10 and C4H8?
A)
B)
C)
D)
They are bubbled through acidified potassium dichromate solution.
They are passed over heated iron.
They are bubbled through bromine solution.
They are bubbled through propanal solution.
10
Polymers formed from monomers with the general formula H2C=CHX
A)
B)
C)
D)
have the same percentage by mass of X as the monomer.
are produced by condensation reactions.
contain C=C bonds.
are more reactive than the monomer.
Which of the following equations represents a cracking reaction?
A)
B)
C)
D)
C6H12 + H2 → C6H14
C6H14 → C4H8 + C2H6
C6H12O6 → 2C2H5OH + 2CO2
C6H13OH → C6H12 + H2O
Which of the following air pollutants are likely to be removed by rain water?
(I) nitrogen dioxide
(II) sulphur dioxide
(III) carbon monoxide
A)
B)
C)
D)
(I) and (II) only
(I) and (III) only
(II) and (III) only
All of the above
11
Part B: Short questions (20%) (Answer ANY FIVE questions in this part)
A student performed an experiment to prepare solid X. The experiment involved the following steps:
Step 1
Step 2
Step 3
Step 4
Step 5
Step 6
Add 25.0 cm3 of 1 M calcium nitrate solution to a beaker.
Add 25.0 cm3 of 1 M sodium hydroxide solution to the calcium nitrate solution.
Collect solid X formed.
Wash solid X with distilled water.
Dry solid X.
Weight solid X.
(a) Suggest ONE method to dry solid X in Step 5.
(b) What is the theoretical mass of solid X produced?
(c) The mass of the solid is lower than the expected value in (b) even the student did the
experiment carefully. Suggest ONE possible reason.
(1 mark)
(2 marks)
(1 mark)
Methylbenzene, C6H5CH3, will react with bromine, Br2, to form various products. One of the major
products is benzyl bromide, C6H5CH2Br.
(a)
(b)
(c)
(d)
Draw the structure of benzyl bromide.
Name the type of the reaction.
State the condition needed for the reaction to occur.
Construct a chemical equation of the above reaction, which gives benzyl bromide as
the major product.
(1 mark)
(1 mark)
(1 mark)
(1 mark)
P is a hydrocarbon compound with a molecular formula of C2H6O. Its reaction with phosphorus
trichloride gives a white fume.
Compound P
?
Compound Q
HCl
PCl3
Compound R
(a) Draw the structural formula of compound P.
(b) Draw the structural formula of compound R.
(c) Compound R can also be produced from the reaction between compound Q and
hydrogen chloride. Draw the structural formula of compound Q.
(d) Suggest a reagent to convert compound P to compound Q.
12
(1 mark)
(1 mark)
(1 mark)
(1 mark)
Three metals, A, B and C are performing the following experiments:
(I) Putting A into solution containing ions of B, no observable change.
(II) Putting B into solution containing ions of C, a grey solid formed.
(III) Putting C into solution containing ions of A, no observable change.
(a) Name the type of reactions.
(b) Arrange the reactivity of the three metals in an ascending order.
(c) Provided that B is alkali metal while C is alkaline earth metals. Write an ionic equation
for the reaction between metal B and solution containing ions of C.
(d) Suggest how you can show that the grey solid formed in experiment (II) is a metal.
(1 mark)
(1 mark)
(1 mark)
(1 mark)
Magnesium fluoride is a white solid while fluorine is a gas at room temperature and one atmospheric
pressure.
(a) Draw the electron diagram of magnesium fluoride and fluorine showing the
outermost electron shell only.
(b) State the type of bonding exists in magnesium fluoride and fluorine respectively.
(2 marks)
(2 marks)
Methanol, CH3OH, is a convenient liquid fuel. An experiment was conducted to determine the enthalpy
change of combustion of liquid methanol. The energy obtained from burning 2.12 g of methanol was
used to heat 1.50 kg of water. The temperature of the water rose from 25.0 oC to 31.4 oC. (The specific
heat capacity of water is 4.18 J oC-1 g-1)
(a) Define the term ‘standard enthalpy change of combustion’.
(b) Using the data above, calculate the enthalpy change for the combustion of
one mole of liquid methanol.
End of Paper
13
(1 mark)
(3 marks)
14