Chemistry KS1

NAME: ……………………………………………. CLASS:………………

KOLEJ TINGKATAN ENAM SHAH ALAM
JALAN TIMUN 24/1

SHAH ALAM, SELANGOR DARUL EHSAN

PENTAKSIRAN SEMESTER 2 STPM 2021

CHEMISTRY 962/2

PAPER 2

DURATION: 1 HOUR 30 MINUTES

Instruction to candidates
DO NOT OPEN THIS QUESTION PAPER UNTIL YOU ARE TOLD TO DO SO

Write your name, I.C number and class in the space provided. For examiner’s use
There are fifteen questions in Section A. For each question, four
choices of answers are given. Choose one correct answer and Section A
indicate it on the multiple-choice answer sheet provided. Answer 1-15
all questions.
Section B
Answer all the questions in Section B. Write your answers in the 16
spaces provided.
17

Answer two out of the 3 questions in Section C. Write your answer Section C
on your examination test pad. Begin each answer on a new sheet
of paper and arrange your answers in numerical order.

This question paper consists of pages TOTAL

Prepared by: Checked by: Validated by

……………………. ……………………………… ……………………......
Dr S.Sumathi
Pn Marini Binti Abdul Ghani Pn Maziah Binti Muhammad Zain

Head of Chemistry Unit Head of Department

SECTION A  15 marks

Answer all the questions in this section. Indicate the correct answer on the objective answer sheet

1. When a mixture of calcium oxide and carbon is heated strongly, calcium carbide is formed
according to equation
CaO (s) + 3C(s)  CaC2 (s) + CO(g)
If the enthalpy of formation of CaO, CaC2 and CO are -151.6 kJmol-1, -14.4 kJmol-1 and
-26.4 kJmol-1 respectively, calculate the enthalpy change for the above reaction which would
produce 1.0 kg of CaC2.
Relative atomic mass: Ca = 40, C = 12, O = 16
A. -1734.4 kJ
B. +1734.4 kJ
C. -111.0 kJ
D. +111.0 kJ

2. The table below shows the radius of six ions.
Ion A+ B+ C2+ X- Y- Z2-
Radius/nm 0.13 0.17 0.14 0.13 0.17 0.14

The ionic compounds AX, BY, and CZ formed have similar lattice structure. Which of the
following series is arranged in decreasing magnitude of lattice energy?
A. AX, CZ, BY
B. BY,CZ,AX
C. CZ, AX, BY
D. CZ, BY, AX

3. Which of the following reactions involves enthalpy of formation?
A. CO(g) + ½ O2(g)  CO2(g)
B. 2N(g) + 3H2(g)  2NH3(g)
C. 2C + 3H2(g)  C2H6(g)
D. NaOH(aq) + CO2(g)  NaHCO3 (aq)

4. Enthalpy values for elements of sodium, chlorine, and sodium chloride are given as follows.
Ionisation energy of Na = +496 kJ mol-1
Electron affinity of Cl + = -349 kJ mol-1
Enthalpy of atomisation of Na = +108 kJ mol-1
Enthalpy of atomisation of Cl = +121 kJ mol-1
Enthalpy of formation of NaCl = -411 kJ mol-1

By using the enthalpy data above, calculate the enthalpy of reaction for the reaction
NaCl(s)  Na+ (g) + Cl- (g)
A. -376 kJ mol-1
B. + 663 kJ mol-1
C. – 787 kJ mol-1
D. + 787 kJ mol-1

5. Below is a list of standard electrode potential at 298 K for copper and iron.

Electrode system E/V
Cu2+(aq)/Cu+(aq) +0.15
Cu2+(aq)/Cu(s) +0.34
Cu+(aq)/Cu(s) +0.52
Fe2+ (aq)/Fe(s) -0.44
Fe3+(aq)/Fe(s) -0.04
Fe3+(aq)/Fe2+(aq) +0.77

Based on the information above, which of the following statements could be correct.

A. Cu(s) is the strongest reduction agent.
B. Fe3+ (aq) is the strongest oxidising agent.
C. Cu2+(aq) is expected to oxidise Fe2+ (aq) to Fe3+ (aq).
D. The electromotive force of the cell Fe(s)/Fe2+ (aq)// Cu+(aq)/Cu(s) is 0.08V.

6. Study the information and the cell diagram below:

V

Copper Platinum

Cu2+ (aq) 1mol dm-3 I II Fe2+ (aq) 1mol dm-3 and
Fe3+ (aq) 1.0 mol dm-3

Half-cell reaction E/V
Cu2+ (aq) + 2e  Cu (s) +0.34
Fe3+ (aq) + e  Fe2+ +0.77

Which of the following statements about the cell above is correct?
A. Electrons flow from electrode II to electrode I.
B. The voltmeter shows a reading of +1.11 V.
C. The cell diagram can be represented by Pt(s)/Fe2+(aq),Fe3+(aq)//Cu2+(aq)/Cu.
D. When a reducing agent is added to beaker II, the voltmeter reading decreases.

7. In the electrolysis of dilute sulphuric acid, how many faradays,F, are required produce 112 cm3
of gas at the anode measured at s.t.p?
1 mol of gas occupies 22.4 dm3 at s.t.p
A. F/25
B. F/50
C. F/100
D. F/200

8. Which of the following statements is correct for the anodisation of aluminium?
A. The electrolyte is aqueous aluminium sulphate.
B. Aluminium forms the anode of the cell.
C. The purpose of the anodisation is to purify the aluminium.
D. Oxidation occurs at the cathode.

9. Which of the following factors best explains the decrease in ionic radii for the elements of Period
3 from sodium to aluminium?
A. Constant total number of electrons but increasing numbers of protons.
B. Increasing strength in the metallic bond.
C. Decreasing charge density of its ion.
D. Increasing power of polarisation of ions.

10. The elements X, Y and Z are in the short period in the Periodic Table and have the following
properties.
(i) The element X has a giant molecular structure.
(ii) The element Y is a metal.
(iii) The element Z is a simple molecule.

Which of the following statements is true concerning X, Y and Z?

A. The element Y acts as an oxidising agent.
B. The order of increasing first ionisation energy is Z, X and Y.
C. The order of increasing basic character of their oxides are Z, X and Y.
D. The order of increasing proton number is X, Y and Z.

11. The table shows the ionisation energy of an element R.

Ionisation energy kJmol-1

First 430

Second 3130

Third 4440

Fourth 5250

Fifth 8160

Sixth 9870

Seventh 11386

The electronic configuration of the element R is

A. 1s22s22p63s2

B. 1s22s22p63s23p3

C. 1s22s22p63s23p64s1

D. 1s22s22p63s23p64s2

12. Which of the following graphs show the variation in electronegativity of the elements in group
17?
A. B.

C. D.

13. The enthalpy change, H for a reaction depends on
1 the initial and final condition of the reaction
2 the presence of a catalyst in the reaction
3 the reaction mechanism
A. 1 only is correct
B. 1 and 2 only are correct
C. 2 and 3 only are correct
D. 1, 2 and 3 are correct

14. Which statements are true concerning the elements of Group 2?
1 The size of the atom and the radius of the ion increases when descending a group.
2 The element in Group 2 act as a reducing agent in its reactions.
3 The reactivity of the elements decreases when descending Group 2
A. 1 only is correct
B. 1 and 2 only are correct
C. 2 and 3 only are correct
D. 1, 2 and 3 are correct

15. A few redox standard potential values are given in the table below.

Electrode reaction E/V

Fe2+(aq) + 2e  Fe(s) -0.44

Fe3+(aq) + e  Fe2+(aq) +0.77

HNO2(aq) + H+ (aq) + e  NO(g) + H2O(l) +0.99

Sn4+ (aq) + 2e  Sn2+(aq) +0.15

Which of the following can oxidise Sn2+ to Sn4+ under standard condition?
1 Acidic aqueous solution of HNO2
2 Aqueous solution of Fe3+
3 Aqueous solution of Fe2+

A. 1 only is correct
B. 1 and 2 only are correct
C. 2 and 3 only are correct
D. 1, 2 and 3 are correct

SCORE:

NAME: …………………………………………….
CLASS:…………………………………………….

SECTION A (Answers)

1 6 11
2 7 12
3 8 13
4 9 14
5 10 15

SECTION B 15 marks
Answer all the questions in this section.
16. The diagram below shows the energy cycle for Halogen Group elements.

½ X2 H2
X- (aq)

H1 He Hhydration
X (g) Electron afinity X- (g)

a) What are represented by H1 and H2 in the energy cycle above? 2 marks

…………………………………………………………………………………………………

…………………………………………………………………………………………………

b) The H values for chlorine and bromine are shown in the table above.

H Cl Br
H1/kJmol-1
He/kJmol-1 121 112
Hhydration/kJmol-1 -364 -342
-381 -351

(i) Calculate the H2 for each of the halogens in the table. 2 marks

(ii) From the values in c(i), explain which halogen formed its ion easily. 2 marks

………………………………………………………………………………………………

................................................................................................................................................

(c) The standard enthalpy of solution of ammonium chloride, NH4Cl is +15 kJ mol-1.
A 2.0 g sample of ammonium chloride is dissolved in 50 g of water. Both substances are
initially at 20oC. Calculate the temperature change and the final temperature of the
solution. Assume that the specific heat capacity of the solution is 4.2 J K-1 g-1. [3 marks]

17 a) A diaphragm cell used in the commercial electrolytic production of chlorine and sodium
hydroxide is shown below.

Cl2 product

NaCl (aq) + NaOH (aq)

(i) The ionic equation for the reaction at the anode is 1 marks
2Cl-  Cl2 + 2e

Write an ionic equation for the reaction at the cathode.

………………………………………………………………………………………………
.

(ii) Why is the porous asbestos diaphragm used in this cell? 1 marks

………………………………………………………………………………………………

.

(iii) Explain why the level of brine in the anode compartment is made higher. 1 marks
…………………………………………………………………………………………….....................

(b) The chlorine gas is collected separately from sodium hydroxide that is formed at the cathode

compartment to prevent a reaction that will occur. Write a balanced equation for the reaction that

occurs when chlorine and sodium hydroxide react at room conditions. 1 marks

…………………………………………………………………………………………………………

(c) In an electrolysis using the diaphragm cell, 1.0 mol of hydrogen gas is produced. Calculate the

mass of chlorine gas that is produced in the same experiment. 2 marks

Section C 30 marks
Answer any two questions in this section.

18. (a) The main source of fluorine is the mineral fluorspar which consists of CaF2

(i) Draw and label a Born-Haber cycle that shows the formation of CaF2 from its elements.
6 marks

(ii) From the data below, calculate the lattice energy of CaF2 2 marks

The enthalpy change of atomisation of calcium = +178 kJmol-1
Electron affinity of fluorine = -328 kJmol-1
Enthalpy change of formation of calcium fluoride = -1220 kJmol-1
The enthalpy change of atomisation of fluorine = +158 kJmol-1
First ionisation energy of calcium = + 590 kJmol-1
Second ionisation energy of calcium = + 1150 kJmol-1

(iii) What is the difference between the lattice energy of calcium fluoride and magnesium

fluoride? 3 marks

(b) O(g) + e  O- (g) H = Exothermic 4 marks
O-(g) + e  O2- (g) H = Endothermic

Explain this observations.

19. (a) The yellow gas, chlorine dioxide, ClO2, has been used for many years as flour-improving
agent in bread making. It can be made in the laboratory by the following reaction.

2AgClO3(s) + Cl2(g) 2AgCl(s) + 2ClO2(g)+ O2(g) H = 0 kJ
(i) Give the oxidation state of Cl in ClO2
1 marks

(ii) Chlorine dioxide disproportionates to form a mixture of chlorate (III) and chlorate(V) ions in
alkaline solution. Write a balanced equation and illustrate the disproportionate reaction that occurs.

4 marks

(iii) Given that the standard enthalpies of formation of AgClO3 and AgCl are −25 kJ mol-1 and
−127 kJ mol-1 respectively. Calculate and comment on the value of the standard enthalpy of

formation of chlorine dioxide. [4 marks]

(b) The standard electrode potentials of the following systems are given below.

System Eo / V

ClO2(aq) + 4H+(aq) + 5e ⇌ Cl-(aq) + 2H2O(l) +1.50

S(s) + 2H+(aq) + 2e ⇌ H2S(aq) +0.14

By using the standard electrode potentials given above, prove that chlorine dioxide in an acidic

solution can reacts with aqueous hydrogen sulphide. Write the half cell and overall equations for the

reaction. [6 marks]

20. (a) The first ionisation energies of the Period 3 elements from sodium to argon are given below.

Element Na Mg Al Si P S Cl Ar
786 1060 1000 1206 1520
First ionisation energy(kJmol-1) 494 736 577

(i) Define first ionisation energy of an element. 1 marks

(ii) Sketch a graph of first ionisation energy of the Period 3 elements and explain your graph. 7 marks

(b) The enthalpies of vaporisation of sodium, aluminium and chlorine are given in the table below:

Element Enthalpy of vaporisation (kJ)
Sodium 103
Aluminium 294
Chlorine 20.4

(i) Discuss the variations in the enthalpies of vaporisation of sodium, aluminium and

chlorine. 4 marks

(ii) Sodium and aluminium react separately with chlorine to form sodium chloride and

aluminium chloride. Which of the compounds has a higher enthalpy of vaporisation?

Explain your answer. 3 marks

END OF QUESTION PAPERS

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