PRACTICE MODULE CHEMISTRY SK015

PRACTICE MODULE CHAPTER 6 SK015
8. A mixture of 3.31 moles of A, 4.33 moles of B, and 5.95 moles of C is placed in a one-liter container at a

certain temperature. The reaction was allowed to reach equilibrium. At equilibrium, the number of moles of
B is 6.16. Calculate the degree of dissociation and equilibrium constant, Kc for the reaction:

A(g) ⇌ 3B(g) + 2C(g)

Ans:α = 0.184, Kc= 4.45 x 103
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PRACTICE MODULE CHAPTER 6 SK015
WORKSHEET 6.2(d)
1. a. What is the equilibrium constant expression, Kc for the reaction:

2Fe(s) + 2NO2(g) ⇌ 2NO(g) + 2FeO(s)

Ans: K= [NO]2/[NO2]2
b. What is the numerical value of the equilibrium constant, Kc, for the reaction:

2SO3(g) ⇌ 2SO2(g) + O2(g)
if the equilibrium constant for the reaction given below is 2.7 x 10-3 ?

1/2O2(g) + SO2(g) ⇌ SO3(g)

Ans: 1.37 x 105
2. For the equilibrium:

2BrCl(g) ⇌ Br2(g) + Cl2(g)
at 205°C, the equilibrium constant, Kc is 0.143. If 1.34 moles each of Br2(g) and Cl2(g) are introduced in a
container which has a volume of 11.0 liters and allowed to reach equilibrium at 205°C, what would be the
concentrations of Br2(g), Cl2(g), and BrCl(g) at equilibrium?

Ans: [BrCl] = 0.139M, [Br2] = 0.0525M, [Cl2] = 0.0524M
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PRACTICE MODULE CHAPTER 6 SK015
3. For the equilibrium:

2NO(g) ⇌ N2(g) + O2(g)
at 300 K, the equilibrium constant, Kc, is 0.185. If 1.45 moles each of N2(g) and O2(g) are introduced in a
container that has a volume of 6.00 liters and allowed to reach equilibrium at 300 K, what are the
concentrations of N2(g), O2(g),and NO(g) at equilibrium?

Ans: [NO] = 0.260M, [N2] = 0.112M, [O2] = 0.112M
4. Kc of the reaction at 900°C is 1.40 x 10-3;

2A(g) ⇌ B(g) + C(g)
If 0.780 mole of A(g) and 0.244 mole each of B(g) and C(g) are mixed in a 1.00 liter container at 900°C, what
are the concentrations of A, B, and C at equilibrium?

Ans: [A] = 1.180M, [B] = 0.0441M, [C] = 0.0441M
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PRACTICE MODULE CHAPTER 6 SK015
5. At 25oC, 0.200 mol of dinitrogen monoxide and 0.560 mol of oxygen gas were placed in a 10.0-L reaction

vessel and allowed to react:
2N2O(g) + 3O2(g) ⇌ 4NO2(g)

When the system reached equilibrium at 25oC, the concentration of nitrogen dioxide was found to be 0.0200
M. What is the value of Kc for the oxidation of dinitrogen monoxide to nitrogen dioxide at 25oC?

Ans: 23.21
6. The value of Kp at 100oC for the following reaction is 6.7 x 10-3.

COCl2(g) ⇌ CO(g) + Cl2(g)
if a reaction vessel is initially filled with only COCl2(g) at 2.3 atm and 100oC, what will be the equilibrium
partial pressures of all three gases?

: 2 = 2.179 , = 0.1208 , 2 = 0.1208
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PRACTICE MODULE CHAPTER 6 SK015
7. 0.60 mol of Br2 and 0.60 mol of Cl2 are placed in a 1.00 L flask and allowed to reach equilibrium. After

reaching equilibrium, the flask is found to contain 0.28 mol of BrCl. What is the value of Kc for this reaction?
Br2(g) + Cl2(g) ⇌ 2BrCl(g)

Ans: 0.371
8. If 2.00 moles of hydrogen and iodine gases are allowed to react in a 10.0 L vessel according to the following

reaction with Kc = 64.0 at a certain temperature, what will be the equilibrium composition?
H2(g) + I2(g) ⇌ 2HI(g)

Ans: [HI] = 0.32M, [H2] = 0.04M, [I2] = 0.04M
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PRACTICE MODULE CHAPTER 6 SK015

6.3 LE CHATELIER’S PRINCIPLE
MIND MAP / i-THINK MAP

FIGURE 1: Apply Le Chatelier’s Principle to Reduce the Disturbance

WORKSHEET 6.3 (a)
1. State Le Chatelier’s Principle.
________________________________________________________________________________________

2. Complete the following chart by writing left, right or none for the following for equilibrium shift, and decreases,
increases or remains the same for the concentrations of reactants and products, and the value of K.

N2(g) + 3H2(g) ⇌ 2NH3(g) ΔH = –22 kJ

Disturbance Equilibrium [N2] [H2] [NH3] K
Shift - decreases increases
Example: right remains the
Add N2 same

Add H2 -

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Add NH3 PRACTICE MODULE CHAPTER 6 SK015
-
Remove -
NH3

Increase
temperature

Decrease
temperature

Increase
pressure

3. Complete the following chart by writing left, right or none for the following for equilibrium shift, and decreases,

increases or remains the same for the concentrations of reactants and products, and the value of K.

H2(g) + I2(g) ⇌ 2HI(g) ΔH = +12.6 kJ

Disturbance Equilibrium [H2] [I2] [HI] K

Shift

Add H2 -

Add I2 -

Add HI -

Remove H2 -

Remove I2 -

Remove HI -

Increase
temperature

Decrease
temperature

Increase
pressure

Decrease
pressure

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PRACTICE MODULE CHAPTER 6 SK015

WORKSHEET 6.3(b)

1. In the following reaction, will the [H2] increase or decrease when equilibrium is reestablished after these
stresses are applied?

N2(g) + 3H2(g) ⇌ 2NH3(g) + 22KJ

a) NH3 is added Answer:

b) pressure is increased Answer:

c) N2(g) is removed Answer:

d) temperature is increased Answer:

2. 2NO(g) + H2(g) ⇌ N2O(g) + H2O(g) + 36KJ

In which direction, left or right, will the equilibrium shift if the following changes are made

a) NO is added Answer:

b) H2 is removed Answer:

c) N2O is added Answer:

d) the system is cooled Answer:

e) pressure is increased Answer:

f) H2 is removed Answer:

3. CO2(g) + H2(g) + heat ⇌ CO(g) + H2O(g)

a) Is heat absorbed or released by the forward reaction? Answer:

b) In which direction will the equilibrium shift if these changes are made?

i) CO is added Answer:

ii) CO2 is added Answer:

iii) H2 is removed Answer:

iv) catalyst is added Answer:

v) temperature is increased Answer:

vi) system is cooled Answer:

vii) pressure is increased Answer:

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PRACTICE MODULE CHAPTER 6 SK015

WORKSHEET 6.3(c)

1. Consider the reaction:

2NO2(g) ⇌ N2O4(g) ∆H = -58.0 kJ

Suggest 4 ways to increase the yield of N2O4.

2. For reaction, 2NO(g) + Cl2 (g) ⇌ 2NOCl (g) ∆H = -77.0 kJ
State the optimal pressure and temperature conditions necessary for maximum production of NOCl?

3. Predict the effect of decreasing the volume of the container for each equilibrium.
a) 2H2O(g) + N2(g) ⇌ 2H2(g) + 2NO(g)

b) SiO2(s) + 4HF(g) ⇌ SiF4(g) + 2H2O(g)

c) CO(g) + H2(g) ⇌ C(s) + H2O(g)

4. Predict the effect of decreasing the temperature on the position of the following equilibria.
a) H2(g) + Cl2(g) ⇌ 2HCl(g) + 49.7 kJ

b) 2NH3(g) ⇌ N2(g) + 3H2(g) ∆ H = 37.2 kJ

c) CO(g) + H2O(g) ⇌ CO2(g) + H2(g) ∆ H = -27.6 kJ

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PRACTICE MODULE CHAPTER 6 SK015

WORKSHEET 6.4
MULTIPLE CHOICE QUESTIONS
1. When the system A + B ⇌ C + D is at equilibrium,

A. the sum of the concentrations of A and B must equal the sum of the concentrations of C and
D

B. the forward reaction has stopped.
C. both the forward and the reverse reactions have stopped.
D. neither the forward nor the reverse reaction has stopped.

2. 2SO3(g) ⇌ 2SO2(g) + O2(g)
The conventional equilibrium constant expression (Kc) for the system as described by the above
equation is
A. [SO2]2/[SO3]
B. [SO2]2[O2]/[SO3]2
C. [SO3]2/[SO2]2[O2]
D. [SO2][O2]

3. Consider the following reversible reaction. In a 3.00 liter container, the following amounts are
found in equilibrium at 400 oC: 0.0420 mole N2, 0.516 mole H2 and 0.0357 mole NH3. Evaluate Kc.
N2(g) + 3H2(g) ⇌ 2NH3(g)
A. 0.202
B. 1.99
C. 16.0
D. 4.94

4. If the equilibrium constant for the reaction
A + 2B ⇌ C + 5/2 D

has a value of 4.0, what is the value of the equilibrium constant for the reaction
2C + 5D ⇌ 2A + 4B

at the same temperature?
A. 0.25
B. 0.063
C. 0.5
D. 8.0

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PRACTICE MODULE CHAPTER 6 SK015

5. At 445oC, Kc for the following reaction is 0.020.
2HI(g) ⇌ H2(g) + I2(g)

A mixture of H2, I2, and HI in a vessel at 445oC has the following concentrations: [HI] = 2.0 M, [H2] =
0.50 M and [I2] = 0.10 M. Which one of the following statements concerning the reaction quotient,
Qc, is TRUE for the above system?
A. Qc = Kc; the system is at equilibrium.
B. Qc is less than Kc; more H2 and I2 will be produced
C. Qc is less than Kc; more HI will be produced.
D. Qc is greater than Kc; more H2 and I2 will be produced

6. A quantity of HI was sealed in a tube, heated to 425oC and held at this temperature until equilibrium
was reached. The concentration of HI in the tube at equilibrium was found to be 0.0706 mol/L.
Calculate the equilibirum concentration of H2 (and I2). For the gas-phase reaction,

H2(g) + I2(g) ⇌ 2HI(g) Kc = 54.6 at 425oC

A. 9.55 x 10-3 M

B. 1.17 x 10-3 M

C. 1.85 x 10-4 M

D. 4.78 x 10-3 M

7. The reversible reaction:

2SO2(g) + O2(g) ⇌ 2SO3(g)

has come to equilibrium in a vessel of specific volume at a given temperature. Before the reaction
began, the concentrations of the reactants were 0.060 mol/L of SO2 and 0.050 mol/L of O2. After
equilibrium is reached, the concentration of SO3 is 0.040 mol/L. What is the equilibrium
concentration of O2?

A. 0.010 M

B. 0.020 M

C. 0.030 M

D. 0.040 M

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PRACTICE MODULE CHAPTER 6 SK015

8. The conventional equilibrium constant expression (Kc) for the system below is:
2ICl(s) ⇌ I2(s) + Cl2(g)

A. [I2][Cl2]/[ICl]2
B. [I2][Cl2]/2[ICl]
C. [Cl2]
D. ([I2] + [Cl2])/2[ICl]

9. Consider the reversible reaction at equilibrium at 392oC:
2A(g) + B(g) ⇌ C(g)

The partial pressures are found to be: A: 6.70 atm, B: 10.1 atm, C: 3.60 atm. Evaluate Kp for this
reaction.
A. 7.94 x 10-3
B. 0.146
C. 0.0532
D. 54.5

10. Kc = 0.040 for the system below at 450oC:
PCl5(g) ⇌ PCl3(g) + Cl2(g)

Evaluate Kp for the reaction at 450oC.
A. 0.40
B. 0.64
C. 2.37
D. 0.052

11. For a specific reaction, which of the following statements can be made about K, the equilibrium
constant?
A. It increases if the concentration of one of the products is increased.
B. It changes with changes in the temperature
C. It increases if the concentration of one of the reactants is increased.
D. It may be changed by the addition of a catalyst.

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PRACTICE MODULE CHAPTER 6 SK015

12. The equilibrium between water and its vapour in an open vessel
A. can be achieved
B. depends upon pressure
C. cannot be achieved
D. depends upon temperature

13. When a catalyst is added to a reversible reaction in equilibrium state the value of the equilibrium
constant
A. increases
B. decreases
C. does not change
D. becomes zero

14. A vessel at equilibrium contains SO3, SO2 and O2, now some helium gas is added so that total
pressure increases while temperature and volume remain constant. According to Le Chatelier
Principle the dissociation of SO32-
A. decreases
B. remain constant
C. increases
D. change unpredictably

15. The chemical equilibrium of a reversible reaction is not influenced by
A. temperature
B. pressure
C. catalyst
D. concentration

16. If heat is added to an exothermic reaction, in which direction will the equilibrium shift according to
Le Chatelier's principle?
A. equilibrium does not shift
B. to the right
C. cannot be determined
D. to the left

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PRACTICE MODULE CHAPTER 6 SK015

17. Which of the following statements best describes Le Chatelier's Principle?
A. When a system is disturbed that was in equilibrium, the system will adjust itself to reduce the
change.
B. Equilibrium cannot be attained following a reaction.
C. The forward rate of a reaction equals the reverse rate of a reaction.
D. A system at rest tends to stay at rest.

18. What will be the result if heat is added to an endothermic reaction?
A. The equilibrium will shift to the left toward the reactants.
B. More products will be made as the equilibrium shifts to the left.
C. The reaction will remain unchanged.
D. More products will be made as the equilibrium shifts to the right.

19. For the reaction below, which change would cause the equilibrium to shift to the right?
CH4(g) + 2H2S(g) ⇌ CS2(g) + 4H2(g)
A. Decrease the concentration of dihydrogen sulfide, H2S.
B. Increase the pressure on the system.
C. Decrease the concentration of carbon disulfide, CS2.
D. Decrease the concentration of methane

20. Consider the following equilibrium reaction equilibrium

Cr2O72- +H2O ⇌ 2CrO42- +2H+

(orange) (yellow)

Which one of the following will cause a yellow colour to predominate?

A. Addition of sodium hydroxide (NaOH)

B. Removal of water

C. Addition of sodium chromate (Na2CrO4)

D. Addition of hydrochloric acid (HCl)

Prepared by : Mdm Siti Fadhilah & Mdm Sharifah Fadthyah

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PRACTICE MODULE CHAPTER 7 SK015

CHAPTER 7: IONIC EQUILIBRIA

MIND MAP (OVERVIEW)

7.1: ACID AND BASES

THEORY ACID BASE
Arrhenius
Substances that dissociate in water Substances that dissociate in
to produce hydrogen ions, H+(aq) water to produce hydroxide ions,
OH-(aq)
Bronsted-Lowry Substance (mole or ion) that can
donate a proton,H+, to a base. A substance that can accept a
proton from an acid.

Lewis A species (an atom, ion or molecule) A species that has an unshared
which can form a dative covalent electron pair which can form a
bond by accepting an electron pair dative covalent bond with an
from a base. [electron-pair acceptor] atom, molecule or ion. [electron
pair donor]

i. H2PO4 + NH3 HPO42 + NH4+
Acid Base conjugate base conjugate acid

ii. HClO + CH3NH2 CH3NH3+ + ClO
Acid Base conjugate acid conjugate base

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PRACTICE MODULE CHAPTER 7 SK015

ACID/BASE STRONG WEAK
EXAMPLES Acid/base that almost completely Acid/base that only partially dissociated
dissociated in aqueous solution. in aqueous solution.
Strong electrolyte Weak electrolyte
Acid: HCl, HBr, H2SO4 & HNO3 Acid: H3PO4, CH3COOH
Base: LiOH, NaOH, KOH Base: NH3, CH3NH2, C2H5NH2

Acid-base equilibrium: HA (aq) + H2O (l) H3O+ (aq) + A- (aq)

Acid dissociation constant,Ka = [H3O+] [A-]
[HA]

Acid-base equilibrium: B (aq) + H2O (l) OH- (aq) + BH+ (aq)

Base dissociation constant, Kb = [ OH-] [BH+]
[B]

Ionisation of water: 2H2O (l) H3O+ (aq) + OH- (aq)

The water ionisation constant, Kw = [H3O+] [ OH -] = 1.0 x 10-14 mol2dm-6 at 250C

The pH scale: pH = -log [H3O+] pOH = -log [ OH-]

pH + pOH = 14 pKa + pKb = pKw = 14

Relationship between pH and pOH to the ionic product of water, Kw at 250C :
pKw = pH + pOH = 14

Kw = 1.0 x 10 -14

Degree of dissociation: α = amount of species dissociated
initial amount of species

Salt hydrolysis

Type of Acid & Type pH Example
Base of salt
Strong acid +
Neutral 7 HCl (aq) + NaOH(aq) → NaCl (aq)
Strong base

Strong acid + Weak < 7 HCl (aq) + NH3(aq) → NH4Cl(aq)
Acidic

base

Weak acid + Strong > 7 CH3COOH (aq) + NaOH (aq) → CH3COONa(aq)
Basic

base

Buffer solution using Henderson – Hasselbalch equation

a) Acidic Buffer solution b) Basic Buffer solution

pH = pKa + log [conjugate base] pOH = pKb + log [conjugate acid]
[weak acid] [weak base]

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PRACTICE MODULE CHAPTER 7 SK015
7.1: ACID AND BASES
WORKSHEET 7.1
1. a) Define acid and base according to the Bronsted-Lowry Theory.

b) Write the formulae for the conjugate bases of the following Bronsted-Lowry acid;
i) HCN : ____
ii) HCO3- : _____
iii) CH3OH: ______

c) Write the formulae for the conjugate acids of the following Bronsted-Lowry base;
i) N2H4 : _______
ii) HCO3- : _______
iii) C5H5N : _______

2. A sample of sea water have a pH of 8.50. Calculate the concentration of hydronium ion
H3O+ and hydroxide ion, OH- in this sample of sea water.
[Ans : [H3O+] = 3.16 x 10−9 M, [OH−] = 3.16 x 10−6 M ]

3. The pH of orange juice is 3.40 at 25˚C. Calculate the concentration of H3O+ and
OH-. [Ans : [ 3 +] = 3.98 10−4 , [ −] = 2.51 10−11 ]

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PRACTICE MODULE CHAPTER 7 SK015

4. The table shows the acid ionisation constant, Ka for several acid.

Acid pKa
HCOOH 3.74
7.54
HOCl 9.21
HCN 1.96
HClO2

a) Arrange them in an increasing order of acidic strength.

b) Give the formula of conjugate base for each acid and arrange them in increasing
order of basic strength.

Acid Conjugate base
HCOOH

HOCl
HCN
HClO2

5. Determine the pH of the following solutions;
a) 0.25 M HNO3 [ Ans : 0.60]

b) 0.125 M Ba(OH)2 [Ans : 13.40]

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PRACTICE MODULE CHAPTER 7 SK015
6. The acid ionisation constant of acetic acid, CH3COOH is 1.8 X 10-5 mol dm-3. Calculate the

pH of 0.325 mol dm-3 CH3COOH solution. [Ans : 2.62]

7. Calculate the pH of 0.1 mol dm-3 ammonia, NH3. Kb = 1.8 X 10-5 mol dm-3 [Ans : 11.12]

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PRACTICE MODULE CHAPTER 7 SK015
8. Aniline, C6H5NH2 is a weak base. A 0.5 M solution of aniline has a pH of 9.28. calculate the

value of Kb for aniline. [ Ans : = 7.22 10−10 ]

9. The pH of 0.015 mol dm-3 phenol, C6H5OH is 5.82. Calculate the acid ionisation constant,
Ka. [Ans : = 1.53 10−10]

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PRACTICE MODULE CHAPTER 7 SK015
10. Calculate the percentage ionisation of 0.2 mol dm-3 nitrous acid, HNO2 solution.

[Ka = 7.14 x 10 -4 mol dm-3] [Ans : 5.8%]

11. A 0.15 mol dm-3 solution of methanoic acid, HCOOH is 0.93% ionised. Calculate the pH of
the solution. [Ans : 2.85]

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PRACTICE MODULE CHAPTER 7 SK015
12. Sodium fluoride, NaF is a salt form when a weak acid, HF is reacted with strong base,

NaOH. What would be expected pH of the NaF? Explain your answer using appropriate
equation.

13. 1.0 mL of 0.1 M NaOH was added into 1.0 L buffer solution containing 0.15 M
sodium ethanoate and 0.1 M ethanoic acid, CH3COOH. Calculate the change in pH of the
solution. [Ka CH3COOH = 1.75 x 10-5] [Ans : 7.159 x 10-4]

7.2: ACID-BASE TITRATION
WORKSHEET 7.2
14. (a) Differentiate between end point and equivalence point in titration.

__________________________________________________________________
__________________________________________________________________

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PRACTICE MODULE CHAPTER 7 SK015
(b) Sketch the titration curve for the titration of 25.00 cm3 of 0.100 mol dm-3 HCOOH

with 0.100 mol dm-3 KOH
(Ka = 1.78 x 10-4)

(c) Sketch the titration curve for the titration of 25.00 cm3 of 0.100 mol dm-3 NH3 with
0.200 mol dm-3 HCl
(Kb = 1.8 x 10-5)

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PRACTICE MODULE CHAPTER 7 SK015
7.3: SOLUBILITY EQUILIBRIA
WORKSHEET 7.3
15. The solubility of PbSO4 in water is 0.038 gL-1. Calculate the

a) Solubility product of PbSO4 [Ans : = 1.573 x 10-8 ]

b) Molar solubility of PbSO4 in 0.01M Pb2+ solution [ Ans : 1.57 x 10-6 M]

16. A 100.0 cm3 of 0.200 mol dm-3 NaF solution is mixed with a 100.0 cm3 of 0.300 mol dm-3
Ca(NO3)2 solution. Does CaF2 precipitate ?
[Ksp for CaF2 is 3.9 x 10-11 ]

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PRACTICE MODULE CHAPTER 7 SK015

WORKSHEET 7.4
OBJECTIVE QUESTIONS

1. Which of the following is amphoteric according to the Bronsted-Lowry definition?
A OH-
B CO32
C SO32
D HSO4-

2. Which of the following is NOT a Lewis acid?
A Cl-
B BF3
C Hg2+
D AlCl3

3. Choose the correct definition of a Bronsted-Lowry acid.
A It is a proton donor.
B It is an electron acceptor.
C It dissolves in water to produce H+ ions.
D It reacts with OH- to produce water.

4. The expression of solubility product silver phosphate, Ag3PO4 is
A  Ag3+ PO43-
B  Ag+3 PO43-
C  3Ag3+ PO43-
D 3 Ag+3 PO43-

5. The pH at equivalence point of a titration of a strong acid and a weak base is
A 10.00
B equal to 7.00
C less than 7.00
D greater than 7.00

6. Which of the following is/are correct for an acid-base indicator?
A Its anion must be of a different colour from its undissociated molecule.
B It must be an ionic compound.
C It must change colour at pH 7.
D It must be a strong base.
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PRACTICE MODULE CHAPTER 7 SK015

For questions 7-10, one or more of three statements I to III may be correct. Choose the most
appropriate answer from the options given.

ABCD

I only I and II only II and III only I, II and III

7. In the reaction between boron trifluoride and ammonia:
BF3 + NH3 → BF3NH3

I BF3 acts as a Lewis acid.
II NH3 acts as a Lewis base.
III A coordinate covalent bond is formed between the BF3 and NH3 molecule.

8. Which of the following factors influence(s) the value of Ka for the dissociation of formic acid?

HCOOH(aq) + H2O(l) HCOO-(aq) + H3O+

I Temperature

II pH

III Initial concentration of HCOO- ion.

9. In a titration, sodium hydroxide solution is introduced into a conical flask containing ethanoic
acid. At the end point, the solution in the flask

I Has a pH more than 7
II Is a buffer solution
III Is not a conductor of electricity

10. Choose the appropriate expression for Ksp when Ag2S, Fe(OH)3 and Mg3(PO4)2 dissolve in
water
I Ksp = [Ag+]2 [ S2-]
II Ksp = [Fe3+] [ OH-]3
III Ksp = [ Mg2+] [ PO43-]2

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PRACTICE MODULE CHAPTER 7 SK015
WORKSHEET 7.5
PSPM CLONE QUESTIONS

1. a) A 25.00 mL of 0.50 M acetic acid, CH3COOH solution is titrated with 0.50 M
sodium hydroxide, NaOH solution. Calculate the initial pH of the acid solution.
Qualitatively, predict the pH of the solution after the addition of 25.00 mL NaOH
solution. Explain your answer. [Ka(CH3COOH) = 1.8 x 10-5]
[9 marks]

b) The pH of a saturated solution of magnesium hydroxide, Mg(OH)2 is 10.52.
Calculate the molarity of Mg(OH)2 in the solution and its solubility product ( Ksp )
[5 marks]

2. a) Calculate the pH of a solution prepared by dissolving 0.5 g of sodium
hydroxide, NaOH, in water using a 250 mL volumetric flask.
[6 marks]

b) Write the equation for the base ionisation of 0.5 M aqueous solution of CH3NH2 and
calculate its pH value. [Kb = 3.7x10−4 M]
[8 marks]

Prepared by : Mdm Afrah & Mdm Nik Khadijah

186