PRACTICE MODUL SK025 2nd Edition

PRACTICE
MODULE

CHEMISTRY

SEMESTER 2 2nd EDITION
SK025

NOOR ASMAHAN * SITI AFIZA * FARHANA * ZANARINA * NORIHAN * NURUL AZWA * WAN ROSILAH

* SUHAINA * NUR ZARIFAH SYAZANA *NOOR SHUHADA * NOOR NAJIHAH * SUHAIBAH * SITI FATIMAH


* SHARIFAH FADTHYAH* JULIANAWATI * SITI FADHILAH

PREFACE

This module is a compilation of exercises in Chemistry
Subject for Semester 2 Session 2022/23. The purpose of
this module is to guide students step by step on how to
answer the questions using specific learning outcomes
as stated in the Curriculum Specifications. Our approach
focuses on understanding and explaining concepts in
Chemistry subject via Mind Map or I-think Map and other
types of exercises. We believe that, understanding the
flow of reaction will make Chemistry an exciting subject
to study and explore. Acknowledgment and appreciation
of real-life applications will lead to realisation that
Chemistry is an ever-expanding and dynamic field of
study. We also appreciate all the efforts made by the
editors:

NOOR ASMAHAN ABDULLAH, FARHANA UMANAN,
ZANARINA SAPIAI, JULIANAWATI AHMED, SITI
AFIZA BASIR, SITI FADHILAH AYUB, SUHAINA
MOHD YATIM, WAN ROSILAH WAN LLAH, NOOR
NAJIHAH KAMARUDDIN, NOOR SHUHADA RAHIM,
SHARIFAH FADTHYAH SYED BAHARUDDIN, SITI
FATIMAH MD SOLLHI, NUR ZARIFAH SYAZANA
HAMZAH, NORIHAN ABDUL GHANI, NURUL AZWA
AHMAD NASIRUDDIN AND SUHAIBAH MUSTAFA

Hopefully, this effort will help all the students in
learning Chemistry Subject with the right method in
Semester 2 and hoping that they score in the final
exam (PSPM 2). Thank you

ALL THE BEST AND GOOD LUCK

i

i

TABLE OF RELATIVE ATOMIC MASSES

Element Symbol Proton number Relative atomic mass
Aluminum Al 13 27.0
Silver Ag 47 107.9
Argon Ar 18 40.0
Arsenic As 33 74.9
Gold Au 79 197.0
Barium Ba 56 137.3
Beryllium Be 4 9.0
Bismuth Bi 83 209.0
Boron B 5 10.8
Bromine Br 35 79.9
Iron Fe 26 55.9
Fluorine F 9 19.0
Phosphorus P 15 31.0
Helium He 2 4.0
Mercury Hg 80 200.6
Hydrogen H 1 1.0
Iodine I 53 126.9
Cadmium Cd 48 112.4
Potassium K 19 39.1
Calcium Ca 20 40.1
Carbon C 6 12.0
Chlorine Cl 17 35.5
Cobalt Co 27 58.9
Krypton Kr 36 83.8
Chromium Cr 24 52.0
Copper Cu 29 63.6
Lithium Li 3 6.9
Magnesium Mg 12 24.3
Manganese Mn 25 54.9
Sodium Na 11 23.0
Neon Ne 10 20.2
Nickel Ni 28 58.7
Nitrogen N 7 14.0
Oxygen O 8 16.0
Platinum Pt 78 195.1
Lead Pb 82 207.2
Protactinium Pa 91 231.0
Radium Ra 88 226.0
Radon Rn 86 222.0
Rubidium Rb 37 85.5
Selenium Se 34 79.0
Cerium Ce 58 140.1
Caesium Cs 55 132.9
Silicon Si 14 28.1
Scandium Sc 21 45.0
Tin Sn 50 118.7
Antimony Sb 51 121.8
Strontium Sr 38 87.6
Sulphur S 16 32.1
Uranium U 92 238.0
Tungsten W 74 183.9
Zinc Zn 30 65.4

LIST OF SELECTED CONSTANT VALUES

Ionization constant for water at 25C Kw = 1.0  10−14 mol2 dm−16
Molar volume of gases
Vm = 22.4 dm3 mol−1 at STP
Speed of light in a vacuum = 24 dm3 mol−1 at room temperature
Specific heat of water
c = 3.0  108 m s−1
Avogadro’s number
Faraday constant = 4.18 kJ kg−1 K−1
Planck constant = 4.18 J g−1 K−1
Rydberg constant = 4.18 J g−1 C−1

Ideal gas constant NA = 6.021023 mol−1

Density of water at 25C F = 96500 C mol−1
Freezing point of water
Vapour pressure of water at 25C h = 6.625610−34 J s

RH = 1.097  107 m−1
= 2.18  10−18 J

R = 8.314 J mol-1 K−1
= 0.08206 L atm mol−1 K−1

 = 1 g cm−3

= 0.00 C

P H2O = 23.8 torr

UNIT AND CONVERSION FACTOR

VOLUME 1 L = 1 dm3
1mL = 1 cm3

ENERGY 1J = 1 kg m2 s−2 = 1 N m= 1  107 erg
1 calorie
1eV = 4.184 J
= 1.602 x 10-19 J

PRESSURE 1 atm = 760 mmHg=760 torr =101 325 Pa = 101.325 kPa =101 325 N m-2

OTHERS 1 faraday (F) = 96 500 C
1 newton (N) = 1 kg m s−2

LIST OF CONTENT Page
1-39
No Chapter 38-64
1 Reaction Kinetics 65-88
2 Thermochemistry 89-125
3 Electrochemistry 126-148
4 Hydrocarbon 149-161
5 Aromatic Compound 162-183
6 Haloalkane 184-199
7 Hydroxy Compunds 200-220
8 Carbonyl 221-236
9 Carboxylic Acid 237-248
10 Amine
11 Amino Acid

ii

PRACTICE MODULE CHAPTER 1 SK025

CHAPTER 1.0

REACTION KINETICS

ENERGY PROFILE DIAGRAM

1

PRACTICE MODULE CHAPTER 1 SK025

FACTOR AFFECTING REACTION RATE
MAXWELL BOLTZMAN DISTIBUTION CURVE

2

PRACTICE MODULE CHAPTER 1 SK025

ARRHENIUS EQUATION

1.1 Rate of Reaction
Worksheet 1

1 Define reaction rate?
Ans:

2. N2O5(g) 2NO2(g) + ½O2(g)
Ans:
What happens to the concentrations of the all the gas with time?

3. For the reaction A(g) B(g), sketch two curves on the same set of axes that
Ans: show:
(a) The formation of product as a function of time
(b) The consumption of reactant as a function of time

3

PRACTICE MODULE CHAPTER 1 SK025

4. Consider the decomposition of N2O5(g)
Ans: 2N2O5(g) → 4NO2(g) + O2(g)

Assume the initial concentration of N2O5(g) is 0.02 mol/L and that none of the

products are present. Make a graph that shows concentrations of N2O5(g), NO2(g),

andO2(g) as a function of time, all on the same set of axes and roughly to scale.

5. Based on the balanced equation:
Ans
2A + B C + 3D

and the following data:

time (s) [C] (M)

0.00 0.218

7.96 0.603

(a) What is the rate of appearance of C?
(b) What is the rate of appearance of D?
(c) What is the rate of disappearance of A?
(d) What is the rate of disappearance of B?

4

PRACTICE MODULE CHAPTER 1 SK025

6. Based on the balanced equation:
Ans:
2X + 4Y 3Z + 5Q

and the following data:

time (s) [Y] (M)

0.00 1.358

11.9 0.407

(a) What is the rate of appearance of Y?
(b) What is the rate of appearance of X?
(c) What is the rate of disappearance of Z?
(d) What is the rate of disappearance of Q?

7. In the reaction X 2Y, the concentration of X at t = 28.0 s and t = 117.5 s is 2.15
Ans: mol dm-3 and 1.08 mol dm-3 respectively. What is the average of the reaction during

this time interval?

8. Write the rate of reaction in terms of the rate of disappearance of reactant and the

rate of formation of products:

a. H2 (g) + I2 (g) 2 HI(g)

b. 5Br- (aq) + BrO3- (aq) + 6 H+ 3Br2(aq) + 3H2O(l)

c. NO(g) + O3(g) NO2(g) + O2(g)

d. N2(g) + 3H2(g) 2NH3(g)

e. 2C2H6 (g) + 7O2(g) 4CO2(g) + 6H2O(l)

Ans:

5

PRACTICE MODULE CHAPTER 1 SK025

9. Consider the reaction between magnesium and hydrochloric acid to form magnesium
Ans
chloride and hydrogen gas. When the rate of formation of hydrogen is increasing 0.32
mol dm-3 s-1, what is the rate of decreasing of hydrochloric acid?

10. Ammonium burns in oxygen to form nitrogen oxide and water.
Ans 4NH3(g) + 5O2(g) → 4NO(g) + 6H2O(g)

(a) Write the differential rate equation for the reaction.
(b) At particular moment, the rate which oxygen disappear is 0.40 mol dm-3 s-1.

What is the rate of disappearance of ammonia and the rate at which water is

formed?

6

PRACTICE MODULE CHAPTER 1 SK025

11. For the reaction : 4NH3(g) + 3O2(g) 2N2(g) + 6H2O (g), The rate of decrease
Ans:
of NH3 is 0.82 mol dm-3 s-1. What is the rate decrease of O2 and the rate of

formation of N2 and H2O.

12. Nitrogen pentoxide gas decomposes to nitrogen dioxide gas and oxgen gas
Ans:
according to the following balanced equation.

2N2N5(g) 4NO2 (g) + O2(g)

(a) Write the differential rate equation for dissociation of N2O5 gas.
(b) If the rate of disappearnace of N2O5 gas is 1.0 X 10-2 mol dm-3 s-1, what is

the rate of formation of NO2 gas under the same condition of temperature

and pressure?

13. Nitrogen monoxide gas is reduced by hydrogen gas to nitogen gas and steam at

9040C.

2NO(g) + 2H2(g) N2(g) + 2H2O(g)

In one experiment, the rate of formation of nitrogen gas at 904 oC was found to be

3.4 X 10-2 mol dm-3 s-1.

(a) Write the differential rate equation for the reaction.

(b) Calculate the rate of disapperance of NO at 9040C.

(c) Predict the rate of disapperance of H2 at 9040C.

7

PRACTICE MODULE CHAPTER 1 SK025

Ans:

14. The rate law below:
Ans:
H2(g)+ 2NO(g) ⟶ N2O(g)+ H2O(g

has been experimentally determined to be rate = k[NO]2[H2]. What are the orders with
respect to each reactant, and what is the overall order of the reaction?

15. A series of experiments is performed for the system 2A + 3B + C ⟶ D + 2E
Ans: ●When the initial concentration of A is doubled, the rate increases by a factor of 4.
●When the initial concentration of B is doubled, the rate is doubled.
●When the initial concentration of C is doubled, there is no effect on rate.

a) What is the order of reaction with respect to each of the reactants?
b) Write an expression for the rate equation.

8

PRACTICE MODULE CHAPTER 1 SK025

16. CH3OH+CH3CH2OCOCH3⟶CH3OCOCH3+CH3CH2OH
Ans:
The rate law for the reaction between methanol and ethyl acetate is, under certain
conditions, experimentally determined to be:

rate=k[CH3OH]
What is the order of reaction with respect to methanol and ethyl acetate, and what is
the overall order of reaction?

17. Nitric oxide and chlorine react to form nitrosyl chloride according to the equation
Ans:
2NO + Cl2 2NOCl

The rate equation for the reaction is:
Rate = k[NO]2[Cl2]

(a) What is the overall order?
(b) What are the unit of k?
(c) What happen to the rate if [Cl2] is doubled?
(d) What happen to the rate if [NO] is doubled?

9

PRACTICE MODULE CHAPTER 1 SK025

18. Consider the reaction A ⟶ B, the rate of reaction is 1.6 X 10-2 M/s, when [A] is 0.35
Ans: M. Calculate the rate constant, k, if:

(a) The reaction is first order in A.
(b) The reaction is second order in A.

19. Consider the following chemical reaction of rusting of iron nail.
Ans: 4Fe(s) + 3O2 (g) ⟶ 2Fe2O3(S)

If the rate of consumption (disappearance) of O2 (g) is 0.065 M/s, what is the
(a) rate of disappearance of Fe(s)?
(b) rate of formation of Fe2O3(S)

20. The decomposition of N2O5 proceeds according to the following equation:
2N2O5(g) → 4NO2(g) + O2(g)

If the rate of decomposition of N2O5 at a particular instant in a reaction vessel is
4.2×10–7 M/s, what is the rate of appearance of (a) NO2, (b) O2?

Ans:

10

PRACTICE MODULE CHAPTER 1 SK025

21. The following data were measured for the reaction of nitric oxide with hydrogen:

(a) Determine the rate law for this reaction.
(b) Calculate the rate constant.
(c) Calculate the rate when [NO] = 0.050 M and [H2] = 0.150 M

Ans:

22. Consider a hypothetical reaction:

a) Determine the rate law expression for this reaction.
11

PRACTICE MODULE CHAPTER 1 SK025

b) What is the order of reaction with respect to A? to B?
c) What is the overall reaction order?

Ans:

23. Acetaldehyde decomposes when heated to yield methane and carbon monoxide

according to the equation:

CH3CHO(g)⟶CH4(g)+CO(g)

Determine the rate law and the rate constant for the reaction from the following

experimental data:

Exp [CH3CHO] mol/L Rate (mol/L s-1)
1 1.75 × 10−3 2.06 × 10−11

2 3.50 × 10−3 8.24 × 10−11

3 7.00 × 10−3 3.30 × 10−10

Ans:

12

PRACTICE MODULE CHAPTER 1 SK025

24. Using the initial rates method and the experimental data, determine the rate law
Ans:
and the value of the rate constant for this reaction:

2NO(g)+Cl2(g)⟶2NOCl(g)

Exp [NO] mol/L [Cl2] mol/L Rate
(mol/L s-1)

1 0.10 0.10 0.00300

2 0.10 0.15 0.00450

3 0.15 0.10 0.00675

13

PRACTICE MODULE CHAPTER 1 SK025

25. Use the provided rate data to derive the rate law for the reaction whose equation is:
OCl−(aq)+I−(aq)⟶OI−(aq)+Cl−(aq)

Exp [OCl-] mol/L [l-] mol/L Rate
(mol/L s-1)
1 0.0040 0.0020 0.00184
2 0.0020 0.0040 0.00092
3 0.0020 0.0020 0.00046

Ans:

26. Consider the reaction: P4 + 6H2 → 4PH3. A rate study of this reaction was
Ans:
conducted at 298 K. The data that were obtained are shown in the table.

Exp [P4] mol/L [H2] mol/L Rate
(mol/L s-1)

1 0.0110 0.0075 3.20x10-4

2 0.0110 0.0150 6.40x10-4

3 0.0220 0.0150 6.39x10-4

(a) What is the order with respect to P4 and H2?
(b) Write the rate law for this reaction.
(c) Determine the value and units of the rate constant, k.

14

PRACTICE MODULE CHAPTER 1 SK025

27. With the given information, determine the rate law, the rate constant, and the

overall reaction order.

2Mg + O2 2MgO

Exp [Mg] mol/L [O2] mol/L Initial Rate
(mol/L s-1)
1 0.10 0.10 2.0x10-3
2 0.20 0.10 4.0x10-3
3 0.10 0.20 8.0x10-3

Ans:

15

PRACTICE MODULE CHAPTER 1 SK025

28. The reaction between C and D is represented as follows:
Ans: C+D E

Exp [C] mol/L [D] mol/L Time Interval Change in conc.
(minutes)
1 0.10 1.0 30 of C (M)
2 0.10 2.0 30 2.5x10-3
3 0.05 1.0 120 1.0x10-2
5.0x10-3

(a) Calculate the rate of reaction of each experiment.
(b) Write the rate law.
(c) State the effect on the concentration rate if the concentration of D is doubled

but the concentration of C remains.

29. At 4000C, an organic compound A decomposes to form another organic compound.
Ans:
The initial rate data are given in the following table.

Exp [A] mol/L Initial Rate (mol/L s-1)

1 1.8 × 10−2 9.0 × 10−4

2 3.0× 10−2 1.5 × 10−3

(a) Calculate the rate constant.
(b) Calculate the rate of decomposition of A when the [A] is 6.8 X 10-3 mol/L

16

PRACTICE MODULE CHAPTER 1 SK025

30. The reaction 2A B is first order in A with a rate constant of 2.8 x 10–2 s–1 at
Ans:
80oC. How long will it take for A to decrease from 0.88 M to 0.14 M?

31. 2N2O5(g) → 2N2O4(g) + O2(g)
Ans: The rate law is: Rate = k[N2O5]. At 45oC, the rate constant for the reaction is
6.22 x 10–4 s–1. If the initial concentration of N2O5 in the solution is 0.100 M, how

many minutes will it take for the concentration to drop to 0.0100 M?

32. Iodine atoms combine to form molecular iodine in the gas phase
Ans:
I(g) + I(g) I2(g)

The rate constant of the reaction is 7.0 x 109 M-1s-1 at 23oC. If the initial

concentration of I was 0.086 M, calculate the concentration after 2.0 min.

17

PRACTICE MODULE CHAPTER 1 SK025

33. At 25oC, hydrogen iodide breaks down slowly to hydrogen and iodine: rate = k[HI]2.
Ans: The rate constant at 25oC is 2.4 x 10–21 L mol-1s-1. If 0.01 mol of HI(g) is placed in a
1.0–L container, how long (in years) will it take for the concentration of HI to reach

0.009 mol L-1?

34. N2O5 decomposes into N2O4 and O2.
Ans: 2N2O5(g) → 2N2O4(g) + O2(g)

At 45oC, k = 6.22 x 10–4 s–1.
If the initial concentration of N2O5 in a carbon tetrachloride solution at 45oC is 0.5 M,

what will the concentration be after exactly one hour?

35. Nitrosyl chloride, NOCl, decomposes slowly to NO and Cl2.
Ans: 2NOCl(g) → 2NO(g) + Cl2(g)

The rate law shows that the rate is second order in NOCl. Rate = k[NOCl]2
The rate constant equals 0.020 L mol–1s–1 at certain temperature. Determine how

many minutes it would take for the NOCl concentration to drop from 0.040 M to

0.010 M.

18

PRACTICE MODULE CHAPTER 1 SK025

36. In a first order decomposition reaction, 50% of a compound decomposes in 10.5
Ans: min.
(a) What is the rate constant of the reaction?
(b) How long does it take for 75.0% of the compound to decompose?

37. Use a value of k = 7.30 x 10–4 s–1 for the first–order decomposition of H2O2(aq) to
Ans: determine the percentage H2O2 has decomposed in the first 500.0 s after the
reaction begins.

38. Ethyl iodide (C2H5I) decomposes at a certain temperature in the gas phase as

follows:
C2H5I(g) → C2H4(g) + HI(g)

From the following data determine the order of the reaction and the rate constant.

TIME (min) [ C2H5I] (M)
0 0.36
15 0.30
30 0.25
48 0.19
75 0.13

Ans:

19

PRACTICE MODULE CHAPTER 1 SK025

39. In decomposition reaction B → products, the following data are obtained:
Ans: t = 0 s, [B] = 0.88 M; t = 25 s, 0.74 M; t = 50s, 0.62 M; t = 75 s, 0.52 M; t = 100 s,
0.44 M; t = 150 s, 0.31 M; t = 200 s, 0.22 M; t = 250 s, 0.16 M.
What is the order of this reaction and its rate constant k?

20

PRACTICE MODULE CHAPTER 1 SK025

40. What is the half–life (in min) of N2O5 if it decomposes with a rate constant of
Ans: 5.7 x 10–4 s–1?

41. Cyclopropane(C3H6) is the smallest cyclic hydrocarbon because its 60oC bond
angles allow only poor orbital overlap, it bonds are weak. As a result, it is thermally
unstable and rearrange to propene:

The rate constant is 9.2 s–1.
(a) What is the half–life of the reaction?

(b) How long does it take for the concentration to reach one-quarter of the

initial value?

Ans:

21

PRACTICE MODULE CHAPTER 1 SK025

42. The thermal decomposition of N2O5 obeys first–order kinetics. At 45oC, a plot of ln
Ans: [N2O5] versus t give slope of – 6.18 x 10–4 min–1. What is the half–life of the
reaction?

43. During a study of ammonia production, an industrial chemist discovers that the
compound decomposes to N2 and H2 in a first–order process. He collects the

following data:

Time (s) 0 1.0 2.0

[NH3] 4.000 3.986 3.974
(mol/L)

(a) Use graphical method to determine the rate constant
(b) What is the half–life for ammonia decomposition?

Ans:

22

PRACTICE MODULE CHAPTER 1 SK025

44. The rate constant of the reaction 2A → B is 51 M–1 min–1 at 24oC.
Ans: (a) Starting with [A] = 0.0092 M, how long will it take for [A] = 3.7 x 10–3 M?

(b) Calculate the half–life of the reaction.

45. The reaction 2HI(g) → H2(g) + I2(g) has the rate law = k[HI]2, with k = 0.079 L mol–
Ans: 1s–1 at 508oC. What is the half–life for this reaction at this temperature when the

initial HI concentration is 0.050 M?

46. Mercury (II) chloride reacts with oxalate ion according to the following equation:

2HgCl2(aq) + C2O42-(aq)→ 2Cl-(aq) + 2 CO2(g) + Hg2Cl2(s)

The results of the experiment are shown in TABLE 1.

TABLE 1

Experiment [HgCl2] [C2O42-] Initial rate
(moldm-3) (moldm-3) (moldm-3 h-1)
I
II 0.632 0.049 1.0x 10-3
III 1.0x 10-3
0.948 0.049 4.0x 10-3

0.632 0.098

i. Determine the order of reaction with respect to HgCl2 and C2O42-.
ii.
iii. Calculate the value of the rate constant.
If the initial concentration of C2O42- is 2.8 M, what is the concentration of
iv. C2O42after 3.25 hours.
Ans:

23

PRACTICE MODULE CHAPTER 1 SK025

47. Define order of reaction and activation energy. The following reaction is first order with

respect to NO2 and zero order with respect to O2.
2N02 + 1/2 O2 → N2O5

In an experiment, the rate constant, k, was determined at different temperatures and

the data were tabulated in TABLE 1.

TABLE 1 k (s-1)
Temperature (K) 1.8 x 10-4
2.7 x 10-3
477 3.0 x 10-2
523 2.6 x 10-1
577
667

Write the rate of law of this reaction and determine graphically the activation energy,
Ea, (in kJ mol-1) for the reaction.

Ans

24

PRACTICE MODULE CHAPTER 1 SK025

1.2 Collision Theory
Worksheet 2

1. Explain collision theory.

Ans:

2. What are the two things that must take place in order for a reaction to take place
Ans: between molecules or atom?

3. Describe how the activation energy of a reaction affects the overall rate of the
Ans: chemical reaction.
4.
The higher the Ea, the more energy required during the collision for the
reaction occur.

The diagram shows the reaction occur.

The following collisions do NOT react. State why.
25

PRACTICE MODULE CHAPTER 1 SK025

(a)
(b)

Ans: (c)

(a) _________________________
(b) ________________________

(c) _______________________

5. Draw Label an Endothermic and Exothermic graph of A + B C + D. Make

sure you include the Products, Reactants, Activation Energy, Activated Complex,

and the Heat of the Reaction (ΔH).

Ans: Endothermic Exothermic

6. A key reaction in the upper atmosphere is
Ans: O3(g) + O(g) → 2O2(g)

The Ea(fwd) is 19 kJ, and ∆Hrxn for the reaction is – 392 kJ. Draw a reaction energy

diagram and calculate Ea(rev).

26

PRACTICE MODULE CHAPTER 1 SK025

7. For the reaction A2 + B2 → 2AB, Ea(fwd) = 125 kJ/mol and Ea(rev) = 85 kJ/mol.
Ans:
Assuming the reaction occurs in one step,

(a) Draw a reaction energy diagram.
(b) Calculate ∆Hrxn.

8. The reaction A → B has a reaction enthalpy of – 64 kJ/mol and an activation
Ans:
energy of 22 kJ/mol.
(a) What is the activation energy of the B → A reaction.

(b) Draw the energy profile for the reaction.

9. For the reversible reaction A + B → C + D, the enthalpy change of the forward
Ans: reaction is +21 kJ/mol. The activation energy of the forward
reaction is 84 kJ/mol.
(a) What is the activation energy of the reverse

reaction?
(b) Sketch the reaction profile of this reaction.

27

PRACTICE MODULE CHAPTER 1 SK025

10. i. Which of the letters a–f in the
diagram represents the potential
energy of the products? ___

ii. Which letter indicates the
potential energy of the activated
complex? ______

iii. Which letter indicates the
potential energy of the reactants?
___

iv. Which letter indicates the
activation energy? ______

v. Which letter indicates the heat
of reaction? ______

vi. Is the reaction exothermic or endothermic? ________
vii. Which letter indicates the activation energy of the reverse reaction? ___
viii. Which letter indicates the heat of reaction of the reverse reaction? ___
ix. Is the reverse reaction exothermic or endothermic? _______

1.3 Factor affecting reaction rate
Worksheet 3
Fill in the blanks.

1. Complete the following table by indicating which factor would have the
greatest impact on the rate of reaction. Choose from concentration,
temperature, surface area or catalyst.

SCENARIO FACTOR
Raw carrots are cut into thin slices for cooking.
Protein is broken down in the stomach by the enzyme
pepsin.
A Woolly Mammoth is found, perfectly preserved, near the
Arctic circle.

28

PRACTICE MODULE CHAPTER 1 SK025

More bubbles appear when a concentrated solution of
hydrochloric acid is added to a magnesium strip than
when a dilute solution of the acid is added.
Exhaust from a car engine passes through a catalytic
converter changing most of the poisonous nitrogen oxides
into nitrogen gas and oxygen gas.
A dust explosion occurs in a saw mill.
Blowing air on a campfire to help get it going.

2. A freshly exposed surface of metallic sodium tarnishes almost instantly if exposed to air
and moisture, while iron will slowly turn to rust under the same conditions. In these two
situations, the__________________ refers to how quickly or slowly reactants turn into
products

3. ___________________ refers to how much solute is dissolved in a solution. If there is
a greater concentration of reactant particles present, there is a greater chance that
__________________ among them will occur. More collisions mean a higher rate of
reaction.

4. Grains of sugar have a greater ___________________ than a solid cube of sugar of the
same mass, and therefore will dissolve quicker in water.

5. Chewing antacid tablets is better than swallowing them whole. Why?
Ans: _________________________________________________________________
6. Explain the effect of temperature on reaction rate using Maxwell-Boltzman Distibution

Curve
Ans:

29

PRACTICE MODULE CHAPTER 1 SK025
7. Draw energy profile diagram showing the difference for an endothermic

reaction in the presence of catalyst and without catalyst.
Ans:

8. Does a catalyst increase reaction rate by the same means as a rise in temperature
does? Explain.

Ans:

9. The following gas−phase decomposition reaction is the first order:
C2H5Cl → C2H4 + HCl

In a table of kinetics data, we find the following values listed for this reaction:
A = 1.58 x 1013 s−1, Ea = 237 kJ/mol.
(a) Calculate the value of the specific rate constant at room temperature 25oC.
(b) Calculate the value of the specific rate constant at room temperature 275oC.
Ans:

30

PRACTICE MODULE CHAPTER 1 SK025

10. Consider the decomposition of NO2 into NO and O2:
2NO2(g) → 2NO(g) + O2(g)

The following data were collected for the reaction.

Rate constant, k Temperature
(L mol–1 s–1 ) (oC)
400
7.8 410
420
10 430
440
14
18

24

Determine graphically the Ea for the reaction.
Ans:

OBJECTIVE QUESTION

Worksheet 4

1. What is rate of reaction?
A. How fast a reaction is
B. How big a reaction is
C. How loud a reaction is
D. How much gas a reaction produces

31

PRACTICE MODULE CHAPTER 1 SK025

2. Which of the following statements is correct?
A. The rate of a reaction decreases with passage of time as the concentration
of reactants decreases.
B. The rate of a reaction is same at any time during the reaction.
C. The rate of a reaction is independent of temperature change.
D. The rate of a reaction decreases with increase in concentration of reactant(s).

3. Which of the following correctly describes processes that happen during reactions?
A. Bonds are broken in reactants, which is an exothermic process that takes in energy
B. Bonds are broken in reactants, which is an endothermic process that gives out
energy
C. Bonds are made in products, which is an endothermic process that takes in energy
D. Bonds are made in products, which is an exothermic process that gives out energy

4. For a reaction: 1/2A → 2B, rate of disappearance of 'A' is related to the rate of
appearance of 'B' by the expression:

A

B

C

D

5. In the formation of S02 by contact process; 2SO2 + O2 → 2SO3, the rate of reaction was

measured as = 2.5 × 10-4 mol L-1s-1. The rate of formation of S03 will be

A. -5.0 × 10-4 mol L-1s-1

B. -1.25 × 10-4 mol L-1s-1

C. 3.75 × 10-4 mol L-1s-1

D. 5.00 × 10-4 mol L-1s-1

6. For a reaction 2A + B 2C, with the rate equation: Rate = k[A]2[B]
A. the order with respect to A is 2 and the order overall is 2.
B. the order with respect to A is 2 and the order overall is 3.
C. the order with respect to B is 2 and the order overall is 2.
D. the order with respect to B is 2 and the order overall is 3.

32

PRACTICE MODULE CHAPTER 1 SK025

7. A reaction was found to be zero order in A. Increasing the concentration of A by a factor
of 3 will cause the reaction rate to __________.
A. remain constant
B. increase by a factor of 27
C. increase by a factor of 9
D. triple

8. The rate law of the overall reaction is k[A][B]0 Which of the following will not increase the
rate of the reaction?
A. increasing the concentration of reactant, A
B. increasing the concentration of reactant B
C. increasing the temperature of the reaction
D. adding a catalyst for the reaction

9. For the reaction A+ 3B 2C, how does the rate of disappearance of B compare to

the rate of production of C?

A. the rate of disappearance of B is 1/2 the rate of appearance of C

B. the rate of disappearance of B is 3/2 the rate of appearance of C

C. the rate of disappearance of B is 2/3 the rate of appearance of C

D. the rate of disappearance of B is 1/3 the rate of appearance of C

10. Given: A + 3B 2C + D

This reaction is first order with respect to reactant A and second order with respect to

reactant B. If the concentration of A is doubled and the concentration of B is halved, the

rate of the reaction would _____ by a factor of _____.

A. increase, 2
B. decrease, 2
C. increase, 4
D. decrease, 4

11. rate = k[A]2
For the reaction for which rate law is given above, a plot of which of the following is a
straight line?

A. 1 versus time.
[ ]

B. [A] versus 1


C. [A] versus time

D. ln [A] versus 1


33

PRACTICE MODULE CHAPTER 1 SK025

12. The decomposition of carbon disulfide, CS2, to carbon monosulfide, CS, and sulfur is
first order with k = 2.8 x 10-7 s-1 at 1000oC.
CS2 CS + S
What is the half-life of this reaction at 1000oC?

A. 5.0 x 107 s
B. 4.7 x 10-6 s
C. 3.8 x 105 s
D. 2.5 x 106 s

13. The half-life for a first-order reaction is 32 s. What was the original concentration if, after
2.0 minutes, the reactant concentration is 0.062 M?

A. 0.834 M
B. 0.069 M
C. 0.091 M
D. 0.075 M

14. Given the following data for this reaction:

NH4+(aq) + NO2-(aq) N2(g) + 2H2O(l)

Exp [NH4+] [NO2-] Rate
1 0.010 M 0.020 M 0.020 M/s
2 0.015 M 0.020 M 0.030 M/s
3 0.010 M 0.010 M 0.005 M/s

The rate law for the reaction is:

A. Rate = k[NH4+][NO2-]
B. Rate = k[NH4+]2[NO2-]2
C. Rate = k[NH4+]2[NO2-]
D. Rate = k[NH4+][NO2-]2

15. A reaction is first order with respect to [X] and second order with respect to [Y]. When [X]
is 0.20 M and [Y] = 0.20 M the rate is 8.00 × 10-3 M/min. The value of the rate constant,
including correct units, is

A. 1.00 M min-1
B. 1.00 M-2 min-1
C. 2.00 M-1 min-1
D. 2.00 M-2 min-1

34

PRACTICE MODULE CHAPTER 1 SK025

16. A substance B decomposes by a first-order reaction starting initially with [B]=2.00M and
after 200 min, [B] becomes 0.15M. For this reaction t1/2 is
A. 53.52 min
B. 50.49 min
C. 48.45 min
D. 46.45 min

17. What is the term that used to refer the number of collisions per unit volume of the
reaction mixture?
A. Collision force
B. Collision frequency
C. Collision energy
D. Collision time period

18. As the temperature of a reaction is increased, the rate of the reaction increases because
the __________.
A. reactant molecules collide less frequently
B. reactant molecules collide more frequently and with greater energy per
collision
C. activation energy is lowered
D. reactant molecules collide less frequently and with greater energy per collision

19. Crushing a solid into a powder will increase reaction rate because:
A. the particles will collide with more energy
B. the orientation of colliding particles will be improved
C. the activation energy barrier will be lowered
D. the powdered form has more surface area

20. Which of the graph shows the decomposition of hydrogen peroxide is catalysed by
adding a small amount of manganese (IV) oxide.

A. C.

35

PRACTICE MODULE CHAPTER 1 SK025

B. D.
21. The minimum amount of energy required for a reaction to proceed.

A. activation energy
B. exothermic energy
C. endothermic energy
D. catalyst
22. For the reaction profile diagram shown, which one of the following statements is correct?

A. A represents the energy of the products, and B is the activation energy.
B. A represents the energy of the reactants and C represents the energy of the products.
C. A represents the energy of the reactants and B represents the energy of the products.
D. B represents the energy of the products and C represents the energy of the reactants.
23. The rate of a chemical reaction normally

A. increases as temperature decreases.
B. decreases when a catalyst is added.
C. increases as reactant concentration increases.
D. decreases as reactant concentration increases.
24. A lump of ignited charcoal which is glowing in air burns more vigorously when lowered
into a bottle of pure oxygen. This is due to an increase in

A. surface area
B. concentration
C. temperature
D. volume

36

PRACTICE MODULE CHAPTER 1 SK025

25. It is generally believed that catalysts increase reaction rates by:
A. removing the activation energy barrier
B. providing an alternate activation energy barrier that is lower than the original barrier
C. lowering the activation energy barrier
D. giving the reacting particles more energy, thus there will be more successful collisions

26. Which reaction is fastest?
A. 1g limestone powder, 100 cm3 of 1 M acid and 30oC
B. 1g limestone solid,100 cm3 of 1 M acid and 40oC
C. 1g limestone powder, 100 cm3 acid of 1 M and 40oC
D. 1g limestone solid, 100 cm3 of acid of 1 M and 30oC

27. Which items correctly complete the following statement? A catalyst can act in a chemical
reaction to:
i. increase the equilibrium constant.
ii. lower the activation energy.
iii. decrease ∆E for the reaction.
iv. provide a new path for the reaction.
A. only I & II
B. only II & III
C. only III & IV
D. only II & IV

28. In the graph showing Maxwell Boltzman distribution of energy, ___________.
I. area under the curve must not change with increase in temperature.
II. area under the curve increases with increase in temperature.

III. area under the curve decreases with increase in temperature.
IV. with increase in temperature curve broadens and shifts to the right

hand side.

A. I,IV
B. II,IV
C. III,IV
D. IV

29. Arrhenius equation shows the variation of ___________________ with temperature?
A. Reaction rate
B. Rate constant
C. Energy of activation
D. Frequency factor

37

PRACTICE MODULE CHAPTER 1 SK025
30. Consider the Arrhenius equation given below and mark the correct option.

= − /
A. Rate constant increases exponentially with increasing activation energy and

decreasing temperature.
B. Rate constant decreases exponentially with increasing activation energy and

decreasing temperature.
C. Rate constant increases exponentially with decreasing activation energy and

decreasing temperature.
D. Rate constant increases exponentially with decreasing activation energy and

increasing temperature

PSPM MODEL QUESTION
Worksheet 5

1 (a) The graph in FIGURE 1 represent the experiment of the reaction of A product.

(i) Based on FIGURE 1, determine the order of the reaction.
(ii) Determine the rate constant of the experiment.
(b) For the reaction P + Q → R, the following data were obtained from the experiment

(c) Calculate the activation energy for a first order reaction, given that the rate constant
is 1.50 x 10-2 s -1 at 27 oC and 3.25 x 10-1 s -1 at 35 oC.

38

PRACTICE MODULE CHAPTER 1 SK025

2 Define activation energy

The rate constant for the forward reaction of a reaction between hydrogen gas and

iodine gas is 138 L mol-1 s-1. The activation energy for the reaction is 165 kJ mol-1 at

700°C.

H2 (g) + I2(g) 2HI(g) ∆H = -98.48 kJmol-1

Sketch and label an energy profile diagram for this reaction.

Determine the activation energy and rate constant for the reverse reaction at 700°C.

(Assume Arrhenius factor, A is the same for both forward and reverse reactions).

3. (a) For a reaction : 4NH3(g) + 3O2(g) 2N2(g) + 6H2O(l)
nitrogen gas was formed at a rate of 0.72 mol L−1s−1.

i. Write the rate differential equation for the above reaction.
ii. Calculate the rate of water formation.
iii. State the relationship between rate of water formation and rate of oxygen

consumption.

(b) A series of experiment was conducted to determine the rate of formation of nitrogen
gas, which is the product of the reaction between nitrogen monoxide gas and
hydrogen gas. The result obtained are tabulated as in TABLE 1:

Specify the order of reaction with respect to NO and H2. Hence write the rate
equation.

(c) The rate constant for a certain reaction is 2.52×10−5s−1at 190°C and 6.30×10−4s−1at
230°C. Calculate the activation energy for the reaction.

Prepared by : Mdm Farhana bt Umanan
Checked by : Mdm Nur Zarifah Syazana bt Hamzah

39

PRACTICE MODULE CHAPTER 2 SK 025

CHAPTER 2.0

THERMOCHEMISTRY

I Think Map 2.1 and 2.2 (✿◠‿◠)

TYPE OF ENTHALPIES CALORIMETRY

WORKSHEET 2.1 : Concept Of Enthalpy
1.

a) What are the reactants and products of the reaction?
Reactants :
Products :

b) What is the enthalpy change for this reaction?

c) Does the reaction is exothermic or endothermic reaction? Explain.

38

PRACTICE MODULE CHAPTER 2 SK 025

d) Write the thermochemical equation for this reaction

2. State the enthalpy of reaction for the thermochemical equation below
a) C2H6(g) + 7/2 O2(g) → 2CO2(g) + 3H2O(l) ∆H = – 3119.6 kJ
b) Ca(s) + Cl2(g) → CaCl2(s) ∆H = – 795 kJ
c) KF(s) → K+(aq) + F- (aq) ∆H = +2 kJ
d) Ca2+ (g) → Ca2+ (aq) ∆H = – 1650kJ
e) ½ Cl2(g) → Cl(g) ∆H = +121.4 kJ
f) H2SO4(aq) + NaOH(aq) → Na2SO4(aq) + H2O(l) ∆H = -57.3 kJ

3. Write the balanced thermochemical equation for the reactions below
a) Enthalpy formation for HCl, ∆Hf = -92.4 kJ mol-1
b) Enthalpy formation for Aluminium Oxide, Al2O3, ∆Hf = -1675.5 kJ mol-1
c) Enthalpy combustion for Ethane, C2H6, ∆Hc = -1560 kJ mol-1
d) Enthalpy atomisation for Nitrogen, N2, ∆Ha = 473 kJ mol-1
e) Enthalpy atomisation for Magnesium ∆Ha = 150 kJ mol-1
e) Enthalpy solution for Calcium Chloride, CaCl2 ∆Hsol = -120 kJ mol-1

4. The complete combustion of acetic acid, HC2H3O2(l), to form H2O(l) and CO2(g) at
constant pressure release 871.7 kJ of heat per mole of HC2H3O2(l).
(a)
a) Write a balanced thermochemical equation for this reaction.

39

PRACTICE MODULE CHAPTER 2 SK 025

b) Draw an enthalpy diagram for the reaction.

WORKSHEET 2.2 : Calorimeter
1. Define heat capacity and specific heat capacity
Tips:

unit for heat
capacity (J°C-1)
Unit for specific
heat capacity
( Jg-1 °C-1)

A piece of aluminum with a mass of 50g and an initial temperature of 90°C is placed
2. into 100mL of water at a temperature of 25°C. The temperature of water rises to

31.30 °C. Determine the specific heat capacity of aluminum.
(ans: 0.897 J/gºC)

Tips :

q lost by
something = q
gained by
something

3. When 137 mL of water at 25 °C is mixed with 82 mL of water at 76 °C, what is the
final temperature of the water? Assume that no heat is lost to the surroundings and
that the density of water is 1.00 g/mL.
(ans: 44.1ºC)

Tips :

Cw at both side
can be
cancelled

40

PRACTICE MODULE CHAPTER 2 SK 025

4. An alloy of unknown composition is heated to 137 °C and placed into 100.0 g of water
at 25.0 °C. If the final temperature of the water was 36.4 °C, and the alloy weighed
2.71 g, what is the specific heat capacity of the alloy? The specific heat of water is
4.18 J/gºC.
(ans : 17.4 J/gºC)

Tips :

Final
temperature of
alloy = final
temperature of
water

Bomb Calorimeter – Enthalpy of combustion question

5. In an experiment, 4.5 g of xylose, C5H10O5 was completely burn in a bomb calorimeter
containing 225.0 mL of water at 29.0 0C. The maximum temperature reached after the
reaction completed was 33.0 0C.

a) Calculate the enthalpy of combustion of xylose in kJ mol-1
(ans : -125.4 kJ mol-1)

Step 1:

Write the
equation
reaction

Step 2:

Calculate
molar mass of
C5H10O5

Step 3:

Find number
of moles of
C5H10O5

Step 4:

Find
temperature
change, ∆T

Step 5:

Calculate heat
released, q

41

PRACTICE MODULE CHAPTER 2 SK 025

Step 6:

Find the
relationship
between
experiment
and theory
(from balance
equation).

b) Write the thermochemical equation for the combustion of xylose

Tips:

Check
balance,
phase & ∆H

6. A 0.1375 g of Magnesium is burn in a constant volume bomb calorimeter that has a
heat capacity of 1769 J °C−1. If the calorimeter contains 300 g of water and the
temperature increases by 1.126°C, calculate the heat of combustion of magnesium in
kJ mol−1.
[The specific heat of water is 4.18 Jg−1°C−1 ; Mr Mg = 24.3 gmol-1]
(ans: −601.61 kJ mol−1)

7. 207.5 g sample of solid aluminium is burned in a constant-volume bomb calorimeter
that has a heat capacity of 1245 J°C-1. The calorimeter contains exactly 500.0 g of

water and the temperature increases by 19.2°C. Calculate the

a) Enthalpy of combustion of aluminium

(ans: -8.332 kJmol-1)

42

PRACTICE MODULE CHAPTER 2 SK 025

b) Enthalpy of formation of Al2O3

(ans: -16.664 kJmol-1)

8.
The enthalpy of combustion of fructose, C8H12O6 is 21.2 kJ mol-1. An amount of 2.63
g of fructose was completely combusted in a bomb calorimeter at 25 °C.
a) Write the thermochemical equation for the reaction.

b) Calculate the final temperature if the calorimeter contains 225.0 mL of water.
(ans: Tf = 25.33 °C)

43