中五 化學試卷 (F5 Chemistry Past Paper)

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Secondary 5
Belilios Public School
Half-yearly Examination, 2015-2016
This paper must be answered in English.
GENERAL INSTRUCTIONS
1. There are TWO sections, Section A and Section B in this paper. You are advised to finish Section
A in about 35 minutes.
2. Section A consists of multiple choice questions in this question paper, while section B contains
conventional questions printed separately in Question-Answer Book B.
3. Answers to Section A should be marked on the Multiple Choice Answer Sheet while answers to
Section B should be written in the spaces provided in Question-Answer Book B. The MC Answer
Sheet for Section A and the Question-Answer Book for Section B will be collected separately at
the end of the examination.
Time allowed: 2 hours
Maximum Marks: 100
4. A Periodic Table is printed on page 2 of this question book. Atomic numbers and relative atomic
masses of elements can be obtained from the Periodic Table.
INSTRUCTIONS FOR SECTION A (Multiple-choice questions)
1. All questions carry equal marks.
2. ANSWER ALL QUESTIONS. You are advised to use an HB pencil to mark all the answers on the
Answer Sheet, so that wrong marks can be completely erased with a clean rubber. You must mark
the answers clearly; otherwise you will lose marks if the answers cannot be captured.
3. You should mark only ONE answer for each question. If you mark more than one answer, you
will receive NO MARKS for that question.
4. No marks will be deducted for wrong answers.
Belilios Public School
Half-yearly Examination, 2015-2016
SECTION B: Question-Answer Book B
INSTRUCTIONS FOR SECTION B
(1) Answer ALL questions in each part. Write
your answers in the spaces provided in this
Question-Answer Book.
(2) Do not write in the margins. Answers
written in the margins will not be marked.
(3) An asterisk(*) has been put next to the
questions where effective communication is
(4) Atomic numbers and relative atomic masses
of elements can be obtained from the
Periodic Table printed on P.2.
Common Physical Constants
Avogadro Constant (L) = 6.02 x10²3 mol-¹
Molar volume of gas at s.t.p. = 22.4 dm³ mol-¹
Molar volume of gas at room temperature and
pressure = 24 dm³ mol-¹
(Class No.)
Answers written in the margins will not be marked.
A bottle of concentrated hydrochloric acid HCl(aq) is shown below:
Density: 1.18 g cm³
1 cm³ of the liquid weighs 1.18 g
The liquid contains 36% of HCI by mass
(a) The bascity of hydrochloric acid is 1. What does it mean?
(b) According to the information on the label, calculate the concentration of the concentrated
hydrochloric acid in mol dm³.
(c) To find out the concentration of the concentrated acid, a laboratory technician first drew
from the bottle a sample of 10.00 cm³ of the concentrated acid and diluted it to 100.0 cm³ in
a volumetric flask. The diluted acid sample was then used to titrate a standard sodium
carbonate solution placed in a conical flask using methyl orange as an indicator. 10.00 cm³
of 1.06 mol dm³ sodium carbonate solution required 20.30 cm³ of the diluted acid sample to
reach the end point.
(i) Briefly describe the procedure in preparing a standard sodium carbonate solution.
Answers written in the margins will not be marked.
Answers written in the margins will not be marked.
What is the color change at the end point?
(iii) Using the titration result, calculate the concentration, in mol dm³, of the concentrated
hydrochloric acid in the bottle.
(d) Suggest a possible reason why the concentration of the concentrated hydrochloric acid in the
bottle calculated in (c)(iii) would be smaller than that obtained from (b) above.
(e) Can the laboratory technician use the similar method as (c)(i) to prepare standard sodium
hydroxide solution to find out the concentration of the hydrochloric acid? Explain.
Answers written in the margins will not be marked.
Answers written in the margins will not be marked.
2. (a) Phosphorus is a Group V element which reacts with sodium vigorously to form trisodium
(i) Draw the electronic diagram of trisodium phosphide.
(Show the outermost shell electrons only)
(ii) Does trisodium phosphide have a high or low melting point? Explain.
(b) Phosphorous also reacts with chlorine to form the following compounds : PC13, PC15 and
POC13. Complete the table below.
Draw the three dimensional
Molecule structure
Shape of the
Bond angle Polar or
Answers written in the margins will not be marked.
Answers written in the margins will not be marked.
(c) The molecular size of simple hydrides of Group V elements increases down the group.
(i) State the trend in boiling points of simple hydrides of Group V elements down the group.
(ii) Explain the trend in part (i).
(iii) NH3 dissolves in water, but PH3 has a low solubility in water. Explain with the help of
suitable diagram.
(d) Ice has a lower density than liquid water. Explain.
Answers written in the margins will not be marked.
Answers written in the margins will not be marked.
Consider the reaction below:
CH3(CH₂)7CH-CH(CH₂)7CO₂CH3(1) + H₂(g)
methyl oleate
At room temperature and pressure, a micro-scale experiment was performed using the set-up
shown below in which 0.080 g of methyl oleate in an organic solvent was allowed to react with
excess H₂(g). The H₂(g) flowed from the inverted measuring cylinder to the reacting flask
through the tubing.
direction of H₂(g) flow
CH3(CH₂)7CH₂CH₂(CH₂)7CO₂CH3(1)
methyl oleate in an organic solvent
(a) State one advantage of conducting this reaction in a micro-scale experiment.
(b) Explain why the right end of the tubing was placed at the uppermost position of the inverted
measuring cylinder.
(c) State an expected observation in the inverted measuring cylinder during the reaction.
(d) Calculate the theoretical volume of H₂(g) needed for the reaction to complete at room
temperature and pressure.
(Molar volume of gas at room temperature and pressure = 24 dm³;
Relative molecular mass: methyl oleate = 296.0)
Answers written in the margins will not be marked.
Answers written in the margins will not be marked.
(e) (i) Sketch, in the graph below, the variation of the volume of H₂(g) in the measuring
cylinder with time from start until the completion of the reaction. You should label this
sketch as 'A'. (The measuring cylinder initially contained 10.0 cm³ of H₂(g). The first
few points have been given in the graph to facilitate the sketch.)
volume of H₂(g) / cm
(ii) In the same graph above, give another sketch as required in (i) but only using 0.040 g
of methyl oleate for the reaction while the other conditions remain unchanged. You
should label this sketch as 'B'.
(f) Give TWO properties of a catalyst.
(iii) Besides using catalyst, suggest one way which can increase the rate of the reaction.
Answers written in the margins will not be marked.
Answers written in the margins will not be marked.
4. (a) Quicklime is used in self-heating cans. The diagram shows a self-heating can designed to
raise the temperature of coffee to 60°C.
ODER IN PARTAGE o out of the wor
wwwgati „Ma
PAPAGBA SA załama
inturadowal
Jak bisa me
JEDNOOSING TOYO
ZOVE RÉSERVE
THE ARCHITENDO HE
The button on the base of the can is pushed. The foil separator breaks, allowing water to mix
with the quicklime. After about 3 minutes, the can is opened by the ring pull.
(i) Explain why the coffee becomes hot.
(ii) Suggest ONE reason why it is NOT possible to re-use this self-heating can.
foll separator
(iii) Given the following data
AH (kJ mol¹)
(1) Define standard enthalpy change of formation (AH)
(II) Calculate the standard enthalpy change of the reaction in the self-heating can.
Ca(OH)₂(s)
Answers written in the margins will not be marked.
Answers written in the margins will not be marked.
4. (b) A 75.0 cm³ sample of 0.50 M nitric acid at 25.0°C was mixed with 50.0 cm³ of 0.50 M
sodium hydroxide solution at 25.0°C in a simple calorimeter. The highest temperature
recorded after mixing was 27.5°C.
(Assume that the specific heat capacity and the density of the resultant solution are 4.2 J g`¹ K-¹
and 1.0 g cm²³ respectively.)
Calculate the standard enthalpy change of the neutralization between nitric acid and
sodium hydroxide.
(ii) If sodium hydroxide solution in the above reaction is replaced with ammonia solution
with equal volume and molarity, would you expect any differences in the value obtained
in (i)? Explain your answer briefly.
Answers written in the margins will not be marked.
132.9 137.3
(227) (261)
144.2 (145)
atomic number
relative atomic mass 相對原子質量
PERIODIC TABLE
197.0 200.6
(257) (258) (259)
(209) (210)
Answers written in the margins will not be marked.
Potassium hydrogencarbonate (KHCO3) can be used to bake bread. Upon heating, KHCO3
decomposes into K₂CO3, H₂O and CO2.
(a) Explain the purpose of using KHCO3 in bread baking.
(b) Write the chemical equation for the decomposition of KHCO3 upon heating.
(c) The enthalpy change of decomposition of KHCO3(s) can be determined indirectly from the
enthalpy changes of the following two reactions:
KHCO3(s) + HCl(aq) → KCl(aq) + H₂O(1) + CO₂(g)
K₂CO3(s) + 2HCl(aq) → 2KCl(aq) + H₂O(1) + CO₂(g)
In an experiment to determine the enthalpy change of Reaction (1), 3.39 g of KHCO3(s) was
added to excess HCl(aq) in an expanded polystyrene cup. The experimental data obtained
are shown below:
Initial temperature of the reacting solution
Final temperature of the reacting solution
Mass of the resulting solution
Specific heat capacity of the contents
(Relative atomic mass : K=39, H=1, C=12 and O=16)
Reaction (1)
....... Reaction (2)
4.3 Jg¹¹ K-¹
Assuming that the heat capacity of the cup used is negligible, calculate the enthalpy
change of reaction (1) from the above data.
Answers written in the margins will not be marked.
Answers written in the margins will not be marked.
In another experiment performed under the same conditions, the enthalpy change of
Reaction (2) was found to be -49.1 kJ mol´¹. Calculate the enthalpy change of
decomposition of KHCO3(s) under the experimental conditions.
According to the literature, the standard enthalpy changes of formation of K₂CO3(s),
KHCO3(s), CO₂(g) and H₂O(1) are as follows:
ΔΗ › 298/kJ mol-¹
(i) Using the given information, calculate the standard enthalpy change of decomposition
of KHCO3(s).
(ii) Suggest why the answers obtained from (c)(ii) and (d)(i) are different.
Answers written in the margins will not be marked.
Answers written in the margins will not be marked.
6. (a) Professor J.F. Daniell invented the Daniell cell in 1836. It was one of the first cells to give a
steady voltage over a long period of time.
electron flow
(II) negative pole
digital multimeter
(as a voltmeter)
(iii) Why is a porous pot used?
zinc sulphate
The above diagram shows a Daniell cell connected to a multimeter.
zinc (negative
Mark on the diagram the direction of electron flow in the external circuit.
copper container
(positive electrode)
(ii) Write ionic half equations for the reactions occurring at positive and negative poles of the
(I) positive pole
sulphate solution
(iv) Will the polarity of the cell be affected if the copper can is replaced by an aluminium can
and the copper (II) sulphate solution by an aluminium sulphate solution? Explain your
Answers written in the margins will not be marked.
Answers written in the margins will not be marked.
(b) The electric circuit is set-up as below. Electrode A is made up of impure copper and B is made
of pure copper while electrode X and Y are made of graphite.
Dilute CuSO4(aq)
(i) Write the half-equations occurring at electrodes X and Y.
(ii) Describe what happens when the gas collected at electrode X is bubbled into iron(II)
sulphate solution in a test-tube. Write a balanced equation for the reaction.
Conc. NaCl(aq)
(iii) Would you expect any colour change in the copper(II) sulphate solution during electrolysis?
Explain your answer.
Answers written in the margins will not be marked.
Answers written in the margins will not be marked.
*7. The progress of the reaction between permanganate ions and oxalate ions can be followed by
colorimetry and titrimetric analysis.
2MnO4 + 5C₂04² + 16H* → 2Mn²+ + 10CO₂ + 8H₂O
Comparing with titrimetric analysis, state the advantages and disadvantages of colorimetry in
rate experiment.
**** END OF SECTION B****
**** END OF PAPER****
Answers written in the margins will not be marked.
Secondary 5
Belilios Public School
Half-yearly Examination, 2015-2016
Suggested Answers
SECTION A (Multiple Choice) (30%)
Time allowed: 2 hours
Maximum Marks: 100
SECTION B (70%)
A bottle of concentrated hydrochloric acid HCl(aq) is shown below:
Density: 1.18 g cm³
1 cm³ of the liquid weighs 1.18 g
The liquid contains 36% of HCl by mass
(a) The bascity of hydrochloric acid is 1. What does it mean?
The number of hydrogen ions produced by one HCI molecule in water is 1. (1)
(b) According to the information on the label, calculate the concentration of the concentrated
hydrochloric acid in mol dm³.
Mass of HCI in 1000 cm³ of the concentrated acid = 1180 x 36% = 425 g (1)
Formula of mass of HCl = 36.5
Concentration = 425 / 36.5 = 11.64 mol dm³³ (1)
(c) To find out the concentration of the concentrated acid, a laboratory technician first drew
from the bottle a sample of 10.00 cm³ of the concentrated acid and diluted it to 100.0 cm³ in
a volumetric flask. The diluted acid sample was then used to titrate a standard sodium
carbonate solution placed in a conical flask using methyl orange as an indicator. 10.00 cm³
of 1.06 mol dm³ sodium carbonate solution required 20.30 cm³ of the diluted acid sample to
reach the end point.
(i) Briefly describe the procedure in preparing a standard sodium carbonate solution.
Weigh accurately the amount of anhydrous sodium carbonate needed and
dissolve it using deionized water / distilled water.
Transfer all the solution made to a volumetric flask, add deionised water /
distilled water to the graduation mark of the flask, and mix the content
thoroughly. (1)
What is the color change at the end point?
Colour change from yellow to orange. (1)
(iii) Using the titration result, calculate the concentration, in mol dm³, of the concentrated
hydrochloric acid in the bottle.
No. of mole of H* present in the diluted acid = 1.06 x (10/1000) x 2 = 0.0212 (1)
Conc. of the acid in the bottle = [0.0212 / (20.30/1000)] x 10 = 10.44 mol dm³ (1)
(d) Suggest a possible reason why the concentration of the concentrated hydrochloric acid in the
bottle calculated in (c)(iii) would be smaller than that obtained from (b) above.
Some HCl(g) escaped from the concentrated acid / HCl(g) is volatile. (1)
(e) Can the laboratory technician use the similar method as (c)(i) to prepare standard sodium
hydroxide solution to find out the concentration of the hydrochloric acid? Explain.
No. Standard sodium hydroxide solution cannot be prepared as in (c)(i) as it absorbs
CO₂ and H₂O in air (deliquescent). (1)
2. (a) Phosphorus is a Group V element which reacts with sodium vigorously to form trisodium
(i) Draw the electronic diagram of trisodium phosphide.
(Show the outermost shell electrons only)
Molecule structure
(ii) Does trisodium phosphide have a high or low melting point? Explain.
(b) Phosphorous also reacts with chlorine to form following compounds: PC13, PC15 and POC13.
Complete the table below.
Draw the three dimensional
High melting point as it has a giant ionic structure. (1)
Shape of the
Trigonal Pyramidal 107.5°
Bipyramidal
Tetrahedral
(c) The molecular size of simple hydrides of Group V elements increases down the group.
Describe the trend in boiling points of simple hydrides of Group V elements down the group.
NH3 has the highest boiling point among the hydrides in Group V. The boiling point
then drops for PH3 and increases again down the group. (1)
(ii) Explain the trend in part (i).
This is because stronger hydrogen bonds exist between NH3 molecules, so more
energy is required to overcome the hydrogen bonds. (1)
The attractive force between other hydrides is weak van der Waals' forces which
increases with molecular size / mass. (1)
(iii) NH3 dissolves in water, but PH3 has a low solubility in water. Explain with the help of
suitable diagram.
NH3 can form hydrogen bonds with water molecules but PH3 cannot. (1)
(d) Ice has a lower density than liquid water at 0°C. Explain.
In ice, water molecules are arranged in a regular open network structure because of
extensive hydrogen bonding. (1)
When ice melts to water, the open structure collapses and the water molecules are closer to
each other, resulting in higher density. (1)
SECTION A: (30%)
1. Element X is in the second period of the Periodic Table. An atom of element Y has six more
protons than an atom of element X. Which of the following statements must be correct?
A. Elements X and Y are in the same period.
B. Elements X and Y have the same number of electrons in the first shell of their atoms.
C. An atom of element Y has six more outermost shell electrons than an atom of element X.
D. The mass number of element Y is six more than that of element X.
Refer to the chemical equation: 2PbO(s) + C(s) → 2Pb(s) + CO₂(g)
N moles of PbO are allowed to react with N moles of C under suitable conditions until the
reaction stops. How many mole of Pb can be formed?
3. 50.0 cm³ of 0.80 mol dm³ NaCl(aq) are mixed with 200.0 cm³ of 0.40 mol dm³³ Na₂SO4(aq).
What is the concentration of Na (aq) ions in the resulting mixture?
A. 0.20 mol dm-³
B. 0.40 mol dm-³ C. 0.60 mol dm³ D. 0.80 mol dm¯
4. Hydrazine (N₂H4) can be used as a rocket fuel. It reacts with oxygen according to the equation:
N₂H4(1) + O₂(g) → 2H₂O(g) + N₂(g)
The following standard enthalpy changes of formation are known:
AH (kJ mol¹)
Calculate the standard enthalpy change of the reaction.
A. -140 kJ mol™¹
B. -433 kJ mol™¹
C. -484 kJ mol™¹
5. In which of the following reaction is zinc hydroxide not behaving as a base?
A. Zn(OH)2 + 2HCl → ZnCl₂ + 2H₂O
B. Zn(OH)₂ + 2NaOH → Na₂Zn(OH)4
C. 3Zn(OH)2 + 2H3PO4 → Zn3(PO4)2 + 6H₂O
D. Zn(OH)₂ + (NH4)2SO4 → ZnSO4 + 2NH3 + 2H₂O
D. -535 kJ mol-¹
6. Which of the following describes correctly the difference between solutions of strong and weak
acids of equal concentration?
A. Strong acid solutions have higher pH than weak acid solutions.
B. Strong acid solutions react with zinc while weak acid solutions do not.
C. Strong acid solutions conduct electricity better than weak acid solutions.
D. Strong acid solution require greater amount of alkali for neutralization compared with weak
acid solutions.
Consider the reaction below:
CH3(CH₂)7CH=CH(CH₂)7CO₂CH3(1) + H₂(g)
methyl oleate
At room temperature and pressure, a micro-scale experiment was performed using the set-up
shown below in which 0.080 g of methyl oleate in an organic solvent was allowed to react with
excess H₂(g). The H₂(g) flowed from the inverted measuring cylinder to the reacting flask
through the tubing.
methyl oleate in an organic solvent
direction of H₂(g) flow
CH3(CH₂)7CH₂CH₂(CH₂)7CO₂CH3(1)
(a) State one advantage of conducting this reaction in a micro-scale experiment.
save cost (on chemicals) / minimize (chemical) hazards / save time on carrying out
experiment / reduce the consumption of chemicals / reduce chemical waste (1)
(No mark for faster rate)
(b) Explain why the right end of the tubing was placed at the uppermost position of the inverted
measuring cylinder.
Prevent sucking back of water. / Prevent water from entering the reacting flask. (1)
(c) State an expected observation in the inverted measuring cylinder during the reaction.
Water level inside the measuring cylinder rises. / The gas volume inside the measuring
cylinder reduces. (1)
(d) Calculate the theoretical volume of H₂(g) needed for the reaction to complete at room
temperature and pressure.
(Molar volume of gas at room temperature and pressure = 24 dm³;
Relative molecular mass: methyl oleate = 296.0)
No. of mole of methyl oleate used = 0.08 / 296 = 2.70 x 104
Minimum volume of H₂(g) required = (0.08 / 296) x 24000 cm³ = 6.49 cm³ (1)
(e) (i) Sketch, in the graph below, the variation of the volume of H₂(g) in the measuring
cylinder with time from start until the completion of the reaction. You should label this
sketch as 'A'. (The measuring cylinder initially contained 10.0 cm³ of H₂(g). The first
few points have been given in the graph to facilitate the sketch.)
Volume of H₂(g) remained / cm
B (6.75 cm³)
Increase the temperature of the reaction mixture (1)
(f) Give TWO properties of a catalyst.
A (3.5 cm³)
(for (e)(i), accept correct graph sketched from the incorrect numerical answer obtained
from (d), if the graphical representation is correct.)
In the same graph above, give another sketch as required in (i) but only using 0.040 g
of methyl oleate for the reaction while the other conditions remain unchanged. You
should label this sketch as 'B'.
(for (e)(ii), accept correct sketch deduced from the ½ of the H₂ consumption in (e)(),
even though the numerical answer obtained in (d), and hence, the final volume of H₂
represented in line "A" is incorrect.)
(for (e)(ii), the initial rate shown on Curve B should be lower than that on Curve A)
Besides using catalyst, suggest one way which can increase the rate of the reaction.
A catalyst is a substance that changes the rate of a reaction without being used up. (1)
A catalyst can alter the rate of a chemical reaction. It remains chemically unchanged
at the end of the reaction / specific in action. (1)
4. (a) Quicklime is used in self-heating cans. The diagram shows a self-heating can designed to
raise the temperature of coffee to 60°C.
ODER IN PARTAGE o out of the wor
(iii) Given the following data
AH (kJ mol¹)
wwwgati „Ma
PAPAGBA SA załama
inturadowal
- The foil separator has been broken.
- Quicklime has reacted with water.
Jak bisa me
JEDNOOSING TOYO
ZOVE RÉSERVE
THE ARCHITENDO HE
The button on the base of the can is pushed. The foil separator breaks, allowing water to mix
with the quicklime. After about 3 minutes, the can is opened by the ring pull.
(i) Explain why the coffee becomes hot.
The reaction between quicklime and water is exothermic. (1)
(ii) Suggest ONE reason why it is NOT possible to re-use this self-heating can.
foll separator
(I) Define standard enthalpy change of formation (AH)
Standard enthalpy change of formation of a substance is the enthalpy change
when one mole of it is formed from its elements in their standard states under
standard conditions.
(II) Calculate the standard enthalpy change of the reaction in the self-heating can.
AH [Ca(OH)₂(s)] - AH {[CaO(s)] -AH³; [H₂O(1)]
= (-987) – (-636) – (-286)
= -65 kJ mol-¹
Ca(OH)₂(s)
4. (b) A 75.0 cm³ sample of 0.50 M nitric acid at 25.0°C was mixed with 50.0 cm³ of 0.50 M
sodium hydroxide solution at 25.0°C in a simple calorimeter. The highest temperature
recorded after mixing was 27.5°C.
(Assume that the specific heat capacity and the density of the resultant solution are 4.2 J g²¹ K-¹
and 1.0 g cm³ respectively.)
(i) Calculate the standard enthalpy change of the neutralization between nitric acid and
sodium hydroxide.
Heat transferred to solution = m × c x (T2₂ - T₁)
(75.0 + 50.0)(1.0) g × 4.2 J g¯¹¹ K¯¹ × (27.5 – 25.0) K
Number of moles of water formed = 0.5 mol dm x (50/1000) dm³ = 0.025 mol
(Sodium hydroxide is the limiting reactant.)
- (1312.5/0.025) J mol¹ = -52.5 000 J mol-¹ = -52.5 kJ mol-¹ (1)
If sodium hydroxide solution in the above reaction is replaced with ammonia solution
with equal volume and molarity, would you expect any differences in the value obtained
in (i)? Explain your answer briefly.
Less heat is given out as some energy is used to ionize the weak alkali, ammonia
Potassium hydrogencarbonate (KHCO3) can be used to bake bread. Upon heating, KHCO3
decomposes into K₂CO3, H₂O and CO₂.
(a) Explain the purpose of using KHCO3 in bread baking.
CO₂ gas produced makes the bread rise / spongy.
(b) Write the chemical equation for the decomposition of KHCO3 upon heating.
2KHCO3(s) → K₂CO3(s) + H₂O(1) + CO₂(g)
(c) The enthalpy change of decomposition of KHCO3(s) can be determined indirectly from the
enthalpy changes of the following two reactions:
KHCO3(s) + HCl(aq) → KCl(aq) + H₂O(1) + CO₂(g)
K₂CO3(s) + 2HCl(aq) → 2KCl(aq) + H₂O(1) + CO₂(g)
In an experiment to determine the enthalpy change of Reaction (1), 3.39 g of KHCO3(s) was
added to excess HCl(aq) in an expanded polystyrene cup. The experimental data obtained
are shown below:
Initial temperature of the reacting solution
Final temperature of the reacting solution
Mass of the resulting solution
Specific heat capacity of the contents
(Relative atomic mass : K=39, H=1, C=12 and O=16)
4.3 Jg¹¹ K¹
Heat absorbed : 27.5 x 4.3 x (25.8 – 20.2) = 662.2 J
AH = +662.2 x 10³ / (3.39 / 100) = + 19.6 kJ mol¹
Assuming that the heat capacity of the cup used is negligible, calculate the enthalpy
change of Reaction (1) from the above data.
Reaction (1)
Reaction (2)
(ii) In another experiment performed under the same conditions, the enthalpy change of
Reaction (2) was found to be -49.1 kJ mol¹. Calculate the enthalpy change of
decomposition of KHCO3(s) under the experimental conditions.
AH=19.6-(-49.1 x 0.5)
= +44.15 kJ mol™¹
According to the literature, the standard enthalpy changes of formation of K₂CO3(s),
KHCO3(s), CO₂(g) and H₂O(1) are as follows:
AH, 298/kJ mol-¹
(i) Using the given information, calculate the standard enthalpy change of decomposition
of KHCO3(s).
AH = 0.5 x [-1146 – 394 – 286 – (-959 x 2)] = +46 kJ mol¹ (1)
(ii) Suggest why the answers obtained from (c)(ii) and (d)(i) are different.
Not performing the experiment in standard conditions. /
Heat transfer with the surroundings. /
The heat capacity of the container was neglected.
(a) Professor J.F. Daniell invented the Daniell cell in 1836. It was one of the first cells to give a
steady voltage over a long period of time.
electron flow
(I) positive pole
Cu²+ (aq) + 2e → Cu(s)
(II) negative pole
digital multimeter
(as a voltmeter)
zinc sulphate
The above diagram shows a Daniell cell connected to a voltmeter.
Zn(s) → Zn²+ (aq) + 2e
Mark on the diagram the direction of electron flow in the external circuit.
zinc (negative
(ii) Write ionic half equations for the reactions occurring at positive and negative poles of the
copper container
(positive electrode)
sulphate solution
(iii) Why is a porous pot used?
To allow the movement of ions to maintain the electrical neutrality. (1)
(iv) Will the polarity of the cell be affected if the copper can is replaced by an aluminium can
and the copper (II) sulphate solution by an aluminium sulphate solution? Explain your
Yes. Aluminium is more reactive than Zinc.
Aluminum will be the negative pole and release electrons to Zinc. (1)
(b) The electric circuit is set-up as below. Electrode A is made up of impure copper and B is made
of pure copper while electrode X and Y are made of graphite.
Dilute CuSO (aq).
(i) Write the half-equations occurring at electrodes X and Y.
X: 2CI (aq) → Cl₂(g) + 2e¯
Y: 2H*(aq) + 2e → H₂(g)
Describe what happens when the gas collected at electrode X is bubbled into iron(II)
sulphate solution in a test-tube. Write a balanced equation for the reaction.
The solution turns from pale green to yellow. (1)
Cl₂(g) + 2Fe²+ (aq) → 2Fe³+ (aq) + 2Cl(aq) (1)
Conc. NaCl (aq)
(iii) Would you expect any colour change in the copper(II) sulphate solution during electrolysis?
Explain your answer.
There is no color change.
As number of mole of copper(II) ions formed at the anode is equal to the number
of moles of copper atoms formed at the cathode. The concentration of blue
copper(II) ions remains constant.
*7. The progress of the reaction between permanganate ions and oxalate ions can be followed by
colorimetry and titrimetric analysis.
2MnO4 + 5C₂04² + 16H* → 2Mn²+ + 10CO₂ + 8H₂O
Comparing with titrimetric analysis, state the advantages and disadvantages of colorimetry in
rate experiment.
The advantages of colorimetry over titrimetric analysis:
For colorimetry, less equipment is required. Only a colorimeter and a sample tube
are used for analysis.
Continuous measurement of the progress of the reaction can be obtained because
there is no need to ‘quench' the reaction.
It can be used to analyse fast reaction.
A smaller amount of chemicals will be used.
The disadvantages of colorimetry over titrimetric analysis:
An expensive colorimeter is required.
Colorimetry can only be used for the reaction with colour change.
Colorimeter needs calibration
Filter with suitable wavelength needs to be chosen
Effective communication
**** END OF SECTION B****
**** END OF PAPER****
7. Which of the following statements are true?
(1) Exothermic reactions are always faster than endothermic reactions.
(2) The rate of a reaction at constant temperature increases as the reaction progresses.
(3) All catalysts must be able to increase the rate of reaction.
A. (1) only
B. (1) and (2) only
C. (1) and (3) only
8. 200 cm³ of 1.0 mol dm³ aqueous hydrogen peroxide was decomposed, catalysed by silver metal
granules. The volume of oxygen produced was measured over a period of time. Graph X was
obtained as shown below.
The experiment was repeated twice with changes and graphs Y and Z were obtained.
Which of the following set of changes could have produced the results shown in graphs Y and Z?
Volume of oxygen (cm³)
200 cm³ of 0.5 mol dm-³ aqueous
hydrogen peroxide with silver granules
50 cm³ of 2.0 mol dm³ aqueous
hydrogen peroxide with silver granules
100 cm³ of 1.0 mol dm-³ aqueous
hydrogen peroxide with powdered silver
100 cm³ of 2.0 mol dm³ aqueous
hydrogen peroxide with powdered silver
B₂H6(g) + 3 O₂(g) → B₂O3(s) + 3 H₂O(1)
B(s) + 3/4 O₂(g) →
1/2 B₂O3(s)
H₂(g) + 1/2O₂(g) → H₂O(1)
9. The enthalpy changes of three reactions under certain conditions are shown below:
B. +614 kJ mol-¹
D. (1), (2) and (3)
100 cm³ of 0.5 mol dm³ aqueous hydrogen
peroxide with powdered silver
100 cm³ of 1.0 mol dm³ aqueous hydrogen
peroxide with powdered silver
200 cm³ of 0.5 mol dm-³
of 0.5 mol dm³ aqueous hydrogen
peroxide with silver granules
200 cm³ of 1.0 mol dm³ aqueous hydrogen
peroxide with silver granules
Enthalpy change
-2170 kJ mol-¹
Which of the following is the enthalpy change of formation of B₂H6(g) under the same
conditions?
A. +42 kJ mol-¹
-635 kJ mol-¹
-286 kJ mol-¹
C. +677kJ mol-¹
D. +1249kJ mol-¹
10. The electrolytic purification of copper involves connecting the impure copper as the anode. A
block of pure copper is used as the cathode.
If the impure copper anode contains iron, zinc and silver, which of the metals, excluding copper,
would dissolve into the electrolyte and which, if any, would fall off unoxidised as anode sludge?
impure anode
11. The apparatus below was set up to collect the gases evolved during electrolysis of concentrated
potassium chloride solution using carbon electrodes.
Dissolve into electrolyte
Iron and Zinc
Iron, Zinc and Silver
electrolyte
Given that one mole of electrons was passed through the electrolyte, what were the volumes of
the gases collected in the respective gas syringes measured at room temperature and pressure?
(Molar volume of gas at room temperature and pressure = 24 dm³)
Anode sludge
Zinc and Iron
Iron and Silver
Volume in syringe 1 /dm³ Volume in syringe 2 / dm³
concentrated potassium
chloride solution
Directions: Q.12 and Q.13 refer to the following information:
The table below gives information about some alkanes and alcohols.
carbon atoms
CH3CH₂CH3
CH3CH₂CH₂CH3
Enthalpy change of
combustion / kJ mol-¹
12. Which of the following deductions can be drawn from the data given in the table?
(1) Each additional -CH₂- group causes an increase of approximately 655 kJ of energ to the
enthalpy change of combustion of the alkanes.
(2) The increase in enthalpy change of combustion due to each additional -CH₂- group for the
alcohols is greater than that observed for the alkanes.
(3) Alcohols release less energy than the corresponding alkanes containing the same number of
carbon atoms in combustion.
A. (1) and (2) only
B. (1) and (3) only
Metal oxide
Lead(II) oxide
Copper(II) oxide
Sodium oxide
CH3CH₂CH₂OH
CH3CH₂CH₂CH₂OH
13. What is the quantity of heat evolved from the combustion of 60 dm³ of propane (CH3CH₂CH3),
measured at room temperature and pressure?
(Molar volume of gas at room temperature and pressure = 24 dm³)
14. A metal oxide was placed into a glass tube and heated strongly while hydrogen gas was passed
Enthalpy change of
combustion / kJ mol-¹
C. (2) and (3) only
The metal oxide turned to a silvery colour after some time. The silvery coloured substance was
dissolved partially with shaking in excess dilute sulphuric acid. What could be the identity of the
metal oxide and the reaction which took place in the glass tube?
15. All the rust (Fe2O3) on the surface of a 100 g block of iron was removed and titrated with 1.00 M
dilute hydrochloric acid. It was found that 25 cm³ of hydrochloric acid was required to react
completely with the rust. What percentage of iron in the block has NOT rusted?
(Relative atomic mass: Fe = 55.8)
1.33 x 105 kJ
D. (1), (2) and (3)
16. Chlorine gas was passed through the experiment setup below, and after a few minutes, coloured
substances were observed in flasks A and B.
What were the solutions contained in flasks A and B?
17. Which of the following compounds has a giant ionic structure?
18. H₂O₂(aq) decomposes into H₂O(1) and O₂(g) in the presence of MnO₂ (s). Two experiments are
performed to study this decomposition under the same conditions, except that 50 cm³ of 2M
H₂O₂(aq) is used in Experiment (1), while 100 cm³ of 1 M H₂O₂(aq) is used in Experiment (2).
Which of the following combinations is correct?
Rate of formation of O₂(g) at the start
Experiment (1) > Experiment (2)
Experiment (1) > Experiment (2)
Experiment (1) = Experiment (2)
Experiment (1) = Experiment (2)
H₂SO4(aq)
conc. H₂SO4
19. Which of the following reaction routes can best be used to prepare barium sulphate from barium
A. Zn(s) + CuSO4(aq) → ZnSO4(aq) + Cu(s)
B. 2C(s) + O₂(g) → 2CO(g)
A. BaCO3(s)
B. BaCO3(s)
C. BaCO3(s)
BaCl₂(aq)
D. BaCO3(s)
BaCl₂(aq)
→ BaSO4(s)
20. For which of the following reactions must its enthalpy change be determined by INDIRECT
C. CH3CH₂OH(1) + 30₂(g) → 2CO₂(g) + 3H₂O(1)
Total volume of O₂(g) formed
Experiment (1) = Experiment (2)
Experiment (1) >Experiment (2)
Experiment (1) = Experiment (2)
Experiment (1) > Experiment (2)
H₂SO4(aq)
Na₂SO4(aq)
D. MgO(s) + 2HCl(aq) → MgCl₂(aq) + H₂O(1)
21. Under standard conditions, complete combustion of 0.050 mol of propane (C3H8) gives 111 kJ of
heat. Which of the following is the standard enthalpy change of formation of propane?
(Standard enthalpy change of formation of H₂O(1) = -286 kJ mol¹¹;
Standard enthalpy change of formation of CO₂(g) = -394 kJ mol‍¹)
A. -106 kJ mol-¹
B. +106 kJ mol-¹
C. -569 kJ mol-¹
22. Potassium peroxiodisulphate (K₂S₂O8) can be obtained from the electrolysis of a saturated
solution of potassium hydrogensulphate (KHSO4).
Which of the following correctly describes the oxidation number of sulphur in KHSO4, and the
electrode at which K₂S₂O8 is produced during the electrolysis?
Oxidation number of S in KHSO4
(1) iron(II) chloride solution
(2) acidified potassium permanganate solution
(3) concentrated nitric acid
A. (1) only
23. Which of the following reagents can be used to distinguish between sodium sulphite and sodium
B. (2) only
Given bond enthalpies :
C=C = 612 kJmol¹; H-H
A. +288 kJ mol-¹
A. (1) and (2) only
C. (1) and (3) only
24. From the given information, calculate the enthalpy change of hydrogenation of ethene.
CH₂=CH₂(g) + H₂(g) → CH3CH3(g)
D. +569 kJ mol-¹
Electrode at which K₂S₂O8 is produced
= 436 kJmol¹;
B. -288 kJ mol-¹
D. (2) and (3) only
C-C = 347 kJmol™¹; C-H 413 kJmol™¹
C. -125 kJ mol-¹ D. +125 kJ mol-¹
25. In which of the following ions do the underlined atoms NOT have an octet structure?
B. (1) and (3) only
B. (2) and (3) only
26. Which of the following statements about the structure of ice is CORRECT?
D. (1),(2) and (3)
A. Within the crystal of ice, each water molecule forms a tetrahedron with 4 other water molecules.
B. Ice forms an open cage atomic crystal structure with its constituent molecules.
C. The water molecules are linked to one another by H-O bonds in the open structure of ice.
D. When ice melts, the space between neighbouring water molecules becomes bigger as energy
has been absorbed to melt the ice.
27. Which of the following correctly indicates the strongest intermolecular forces that occur in the
Directions: Each question below (Question Nos 28 to 30) consists of two separate statements.
Decide whether each of the two statements is true or false; if both are true, then decide whether or
not the second statement is a CORRECT explanation of the first statement. Then select one option
from A to D according to the following table :
1st statement
Aluminium oxide is soluble in water.
A. Both statements are true and the 2nd statement is a correct explanation of the 1st statement.
B. Both statements are true and the 2nd statement is NOT a correct explanation of the 1st statement.
C. The 1st statement is false but the 2nd statement is true.
Both statements are false.
The boiling point of hydrogen chloride
is higher than that of hydrogen fluoride.
Diamond is harder than
buckminsterfullerene (C60).
Disperion forces
Hydrogen bonding
Dipole-dipole forces
Dispersion forces
2nd statement
Aluminium oxide is an amphoteric oxide.
The molecular size of hydrogen chloride is greater
than that of hydrogen fluoride.
Diamond has giant covalent structure while
buckminsterfullerene (C60) has a molecular structure.
**** END OF SECTION A ****