NAMA : ______________________________________________________

KELAS : L6____

SMK ST. JOSEPH KUCHING

2024 STPM SEM 1 TRIAL EXAMINATION 962/2

CHEMISTRY
PAPER 2
November 2024

1
1 Hours One and a half hours
2

Instructions to candidates:
For examiner’s use
DO NOT OPEN THIS QUESTION PAPER
UNTIL YOU ARE TOLD TO DO SO
Section B
There are fifteen questions in Section A. For each question,
four choices of answers are given. Choose one correct answer 16
and indicate it on the multiple-choice answer sheet provided.
Read the instructions on the Multiple−choice Answer Sheet very
17
carefully. Answer all questions. Marks will not be deducted for
wrong answer.
Section C
Answer all questions in Section B. Write your answers in the
spaces provided. 18

Answer any two questions in Section C. All working should be 19

shown. Numerical answer should be given to an appropriate
number of significant figures, unit should be quoted wherever
appropriate. Begin each answer on a fresh sheet of paper and 20
arrange your answers in numerical order.
Total

This question paper consists of 10 printed pages

 Section A [15 marks]
Answer all questions in this section.
1 Urea, (NH2)2CO, reacts with water according to the following equation.
(NH2)2CO (s) + H2O (l) → CO2 (g) + 2 NH3 (g)
Calculate the concentration of the ammonia solution produced when 3g of urea reacts
completely with 250 cm3 of water. (Assume that the CO2 produced does not dissolve in
water)
A 0.1 mol dm-3
B 0.2 mol dm-3
C 0.3 mol dm-3
D 0.4 mol dm-3

2 An element M forms a sulphate compound with the formula MSO₄ and ion of M
formed has five valence electrons. Which of the following is the electron configuration
of the neutral atom M?
A 1s2 2s2 2p6 3s2 3p5
B 1s2 2s2 2p6 3s2 3p63d7
C 1s2 2s2 2p6 3s2 3p6 3d5 4s2
D 1s2 2s2 2p6 3s2 3p6 3d7 4s2

3 Coordinate bonds do not exist in

A Al2Cl6 C [Cu(NH3)4]2+
B NH4+ D PCl4+

4 Which of the following does not have sp3 hybridisation of the central atom?
A Methane, CH4
B Boron trifluoride, BF3
C Ammonia, NH3
D Water, H2O

5 Which of the following is true about graphite?

A The carbon-carbon angle is 109°
B It has a higher density than diamond
C It has hexagonal carbon rings arranged in layers
D Each carbon atom uses four sp3 hybrid orbitals to form covalent bonds

6 A 2.5 dm3 vessel contains 16.0 g of oxygen at 300K. 4.0g of hydrogen is then forced
into the vessel. Calculate the total pressure of the mixture at 300K, if the volume of the
vessel remains the same. [The gas constant, R= 8.31 J K-1 mol-1]
A 2485 kPa C 2493 kPa
B 2490 kPa D 2497 kPa

1
7 Which of the following correctly shows the shape of the Maxwell-Boltzmann
distribution curve for two different temperatures (T2 > T1)?
A C

B D

8 The equation for the reaction between nitrogen monoxide and hydrogen is shown as
below.
2NO (g) + 2H2 (g) → 2H2O (g) + N2 (g)
The following data is obtained based on the above reaction.
[NO] (mol dm-3) [H2] (mol dm-3) Initial rate of reaction (mol dm-3 s-1)
0.1 0.1 1
0.3 0.1 9
0.3 0.2 18
The rate law for the above reaction is
A rate = k [NO][H2]
B rate = k [NO]2[H2]
C rate = k [NO]2[H2]2
D rate = k [2NO]2[2H2]2

9 A container contains SO2, O2 and SO3 in equilibrium according to the following

2 SO2 (g) + O2 (g) ⇌ 2 SO3 (g)

equation:
∆H= -197 kJ
What will happen when the temperature of the container is increased?
A The rate of forward reaction remains constant but the rate of the backward reaction
increases.
B There is no effect on the position of the equilibrium.
C The equilibrium constant decreases.
D More SO3 will be produced.

2
10 The graph below shows the concentration of a reactant, P with time.

The rate constant is

A 1.00 moldm-3s-1 C 1.50 moldm-3s-1
B 1.33 moldm-3s-1 D 2.00 moldm-3s-1

11 What will happen, if solid sodium ethanoate is added to an aqueous solution of ethanoic
acid?
A The pH of the solution will increase
B The degree of dissociation of ethanoic acid will increase
C The acid dissociation constant of ethanoic acid will increase
D The H+ ion concentration will increase

12 The equilibrium equation for a saturated solution of magnesium hydroxide is shown

Mg(OH)2(s) ⇌ Mg2+ (aq) + 2OH-(aq)

below.

Which statement is true of the equilibrium equation?

A The solubility product is Ksp = 2x2
B Mg(OH)2 is less soluble when NH4Cl is added.
C Mg(OH)2 is more soluble when NaOH is added.
D The pH of the saturated solution increases with temperature

3
13 The liquid-vapour phase diagram of a mixture of 1-propanol and water is shown below.

What is the distillate obtained if a solution which contains equal masses of 1-propanol
and water is fractionally distilled?
A A mixture with 0.72 mole fraction of 1-propanol
B A mixture with 0.77 mole fraction of water
C 1-propanol
D Water

14 The rate equation for the reaction 2XO2 + O3 → X2O5 + O2 is given as:
Rate = k[XO2][O3]
Which of the following mechanisms is consistent with the above rate equation?
A XO2 + XO2 → X2O4 fast
X2O4 + O3 → X2O3 + O2 slow
B XO2 + O3 → XO5 fast
3
XO5 + XO5→ X2O5 + O2 slow
2
C XO2 + O3 → XO3 + O2 slow
XO2 + XO5 → X2O5 fast
D XO2 + O3 → XO5 slow
XO2 + XO5 → X2O5 + O2 fast

15 An aqueous solution containing X2+ ions form a precipitate when an aqueous solution of
sodium hydroxide is added to it. The solubility of the precipitate is 9.86 x 10 -3 gdm-3 and
its solubility product is 1.96 x 10-11 mol3 dm-9 at 25ºC. What is the relative molecular
mass of the precipitate?
A 31.3 C 74.0
B 58.0 D 99.4

4
Name:
Answer for Section A
Circle the correct answer.

1. A B C D
2. A B C D
3. A B C D
4. A B C D
5. A B C D
6. A B C D
7. A B C D
8. A B C D
9. A B C D
10.
A B C D

11.
A B C D

12.
A B C D

13.
A B C D

14.
A B C D

15.
A B C D

5
 Section B [15 marks]
Answer all questions.
16 Diagram below shows several line spectra of Balmer series in the emission spectrum
of hydrogen atom.

(a) From the energy level diagram above, sketch the transition of electron for the
formation of line spectrum X.
[3]

(b) Calculate the energy required for the transition of an electron to form line
spectrum X in Balmer series.
[4]

(c) Sketch the line spectra in the emission spectrum of lithium ion, Li 2+.
[1]

17 (a) The table below gives the temperature and pressure for the critical point and the
triple point of carbon dioxide.

Stage Triple point Critical point

Temperature (°C) -57 31
Pressure (atm) 5 73

(i) Sketch and label the phase diagram of carbon dioxide.

[3]

(ii) What is meant by triple point?

[1]

6
 (b) State two major differences between the phase diagram of CO 2 and water.
[2]

(c) State one use of dry ice.

[1]

Section C [30 marks]

Answer two questions only.
You may answer all the questions but, only the first two answers will be marked. Write the
answers on the answer sheets provided. Begin each answer on the new page of the answer
sheet.

1 (a) Carbon atom uses hybrid orbitals to form organic compound such as propyne,
8 CH3C≡CH. Using energy level diagram and hybrid orbitals diagram, describe
the hybridisation involved and state the shapes and angle for each carbon
involved.
[7]

(b) Both nitrogen and ethyne molecules contain triple bonds. The reactivity of
nitrogen is lower than that of ethyne. Explain this difference in reactivity.
[2]

(c) Nitrogen oxide can form as nitrogen dioxide, NO2 and nitrate ion, NO3-. By
drawing the Lewis diagram for both NO2 and NO3-, state the shape and angle for
both molecules involved.
[6]

7
1 (a) The decomposition of trichloroethanoic acid (CCl 3COOH) into carbon dioxide
9 and trichloromethane follows a first order mechanism with a half-life of 3 hours
at 80°C.

(i) Write the rate equation for the decomposition of trichloroethanoic acid.
[1]

(ii) Calculate the fraction of the trichloroethanoic acid remain acid after 12
hours.
[2]

(b) In another reaction, A → B, the initial rate is 1.7x10 -4 mol dm-3 s-1 when the
concentration of A is 0.25 mol dm-3.

(i) Calculate the rate of reaction when the concentration of A is 0.75 moldm -3
if the reaction is second order with respect to the concentration of A.
[4]

(c) The following data refers to the reaction between hydrogen gas and nitrogen gas
to form ammonia gas with and without catalyst.

ΔH (kJ mol-1) Catalyst Activation energy (kJ mol-1)

-92 None 350
-92 Iron 160
(i) By using collision theory, explain the effect of adding a catalyst (iron) to
the rate of reaction.
[4]

(ii) This reaction involves a heterogenous catalysts, iron with nitrogen and
hydrogen gas. Explain how do heterogenous catalyst work. [4]

2 (a) Define Kw and explain why when the temperature increases, the K w value also
0 increases.
[3]

(b) A solution was prepared by mixing 100 cm3 of 0.03 mol dm-3 methanamine
solution with 100 cm3 of 0.01 mol dm-3 of hydrochloric acid. Calculate the pH
of the aqueous solution formed at 25 °C. The base dissociation constant, K b for
methanamine is 4.30 x 10-4 mol dm-3 at 25 °C.
[8]

8
 (c) H2O (g) + C (s) ⇌ H2 (g) + CO (g) ∆H= +131 kJ mol-1

Explain the effect on the position of equilibrium for the above reaction if

(i) the total pressure of the system is increased [2]

(ii) the total temperature of the system is increased [2]

END OF QUESTION PAPER

Answer
Section A
Answer
1 D 6 C 11 A
2 C 7 B 12 D
3 D 8 B 13 A
4 B 9 C 14 D
5 C 10 A 15 B

9
Section B
No Answer Mark
16
(a)

Draw energy level line from n=1 to n=5, sketch the energy axis 1
Show the lines getting nearer for higher energy level 1
Show the transition of electron from n=5 to n=2 1

(b) 1
1
1
1

(c)
1

Total marks
8

No Answer Mark

10
 1
(a)
(i)

Correct axes 1
Corret plot 1
Correct label solid, liquid and gas 1

(a) The temperature and pressure where solid , liquid and gas exist in 1
(ii) equilibrium

(b) The solid- liquid line for carbon dioxide has a positive slope/gradient 1
while for water has a negative slope/gradient
The triple point pressure for carbon dioxide is at 5atm/higher than 1 atm 1
while for water is at atm

(c) Uses of dry ice : Refrigerant for food stuff// special effect of white fog in 1
entertainment industry // used as fire extinguisher to put off fire //cloud
seeding to induce rainfall ( any one )

Section C

11
No Answer Mark
18
(a) 1

m4: Draw orbitals with hybrid diagram for C1 1

m5: draw orbitals hybrid diagram for C2 and C3 1
m6: label sigma bond and pi bond 1
m7: stating C1 tetrahedral: C2 and C3 linear 1

(b) nitrogen has strong triple bond 1

high bond energy 1

(c) Draw Lewis diagram of NO2

Molecular geometry: Bent shape/ V-shape 1

Angle: 104°-119° 1

Draw Lewis diagram of NO3-

1

1
Molecular geometry: Trigonal planar
1
Angle: 120°
15
Total marks

12
moldm-3s-1

13
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