SCH4U Lesson 18 Assignment

In this assignment you are going to continue your study of Acid-Base Equilibrium

Total Marks: 122 marks

Instructions:
After completing the lesson action section, you are ready to complete your lesson assignment. Follow these steps:
a) In the textbox given, explain the strategy that you used to determine your answer.
b) Fill in your answer. The mark for each question is given at the introduction to the questions.
c) When finished answering all your questions, save your file and upload the file into the appropriate dropbox.

Part A (Terminology): Matching: (44) using your readings, match each term and the definition provided. The name of
the term is given in the table and the definitions are listed below. Match the name of the term and its corresponding
definition. As part of your answer, identify source of your information. Each question is worth 2 marks. One for the
matching and one mark for your proof.

Match each item to the correct statement below.

a. strong acid f. weak acid
b. polyprotic acid g. proton acceptor
c. strong base h. weak base
d. monoprotic acid i. anion
e. percent dissociation j. cation

____ 1. an acid that yields one proton when it ionizes

D

____ 2. a positively charged ion

J

____ 3. a ratio of the molecules that dissociate into ions at equilibrium to the initial concentration of the acid
E

____ 4. a substance that accepts a hydrogen ion

G

____ 5. an acid that yield two or more protons when it ionizes

SCH4U Lesson Assignment Page 1

 B

____ 6. an acid that dissociates completely into ions in water

A

____ 7. an acid that dissociates slightly into ions in water

F

____ 8. a base that ionizes completely in water

C

____ 9. a base that ionizes slightly in water

H

____ 10. a negatively charged ion

I

Part B (Acid-Base Reactions): Multiple Choice: ( 38 marks) each question is worth 2 marks. One mark for the
strategy and one mark for the final answer.
Identify the choice that best completes the statement or answers the question. Your choices are given below the
text box. Make sure you include your strategy.

____ 1. Which of the following substances is a Brønsted-Lowry acid?

A Bronsted-Lowry acid is a substance that donates a proton (H⁺ ion) in a chemical reaction. H2S (hydrogen
sulfide) can donate a proton to form its conjugate base, HS⁻ (hydrogen sulfide ion), making it a Bronsted-
Lowry acid.

a. CO32–(aq)
b. CH3COO–(aq)
c. H2S (aq)
d. C6H5NH2 (aq)
e. none of the above

SCH4U Lesson Assignment Page 2

____ 2. Which of the following substances can act as a Brønsted-Lowry base?
A Bronsted-Lowry base is a substance that accepts a proton (H⁺ ion) in a chemical reaction. Water (H2O)
can accept a proton to form its conjugate acid, H3O⁺ (hydronium ion), making it a Bronsted-Lowry base.

a. HClO4(aq)
b. HOCl(aq)
c. H2O(l)
d. H3O+(aq)
e. none of the above

____ 3. Which is not characteristic of a base?

Option c. Bases are substances that can accept protons (H+ ions) from other substances. But they contain
the hydroxide ion (OH-) in their chemical formula.

a. has a slippery feel

b. has a bitter taste
c. contains H in the formula
d. is a proton acceptor
e. has a high pH

____ 4. Which of the following substances is not a Brønsted acid?

The correct answer is c. NO3^- (aq). A Bronsted acid is a substance that donates a proton (H⁺ ion) in a
chemical reaction. NO3^- (aq) is the nitrate ion, and it doesn’t contain any hydrogen ions to donate, so it
can’t act as a Bronsted acid.

a. HF(aq)
b. H2SO3(aq)
c. NO3–(aq)
d. NH4+(aq)
e. All of the above are Bronsted acids.

____ 5. Which is a true statement?

SCH4U Lesson Assignment Page 3

 The correct answer is option a. Some substances can act as both an acid and a base. These substances are
called amphoteric substances. They have the ability to donate or accept protons depending on the
conditions they are in. Water is an example of an amphoteric substance. It can act as an acid by donating a
proton or as a base by accepting a proton. So, substances can have the ability to act as both acids and bases.

a. Some substances can act as both an acid and a base.

b. A substance that acts as an acid cannot also act as a base.
c. Water is neutral, and cannot act as an acid or a base.
d. All substances can act as acids or bases.
e. A substance that donates a proton is a base.

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____ 6. Which of these occurs during the formation of H3O+ (aq)?
When H3O+ (hydronium ion) is formed in an aqueous solution, it occurs through the process of ionization,
where a water molecule (H2O) dissociates into H+ ion and OH- ion, and the proton is transferred to another
water molecule, forming a hydronium ion (H3O+)

a. ionization
b. dissociation
c. association
d. a and b
e. a, b, and c

____ 7. In the autoionization of water, the concentration of hydronium ions _______ if the concentration of hydroxide
ions increases.
When the concentration of hydroxide ions (OH^-) increases (according to Le Chatelier’s Principle), the
equilibrium shifts to the left to counteract the increase in OH^- ions. As a result, the concentration of
hydronium ions (H3O^+) decreases to maintain equilibrium. So, if the concentration of hydroxide ions
increases, the concentration of hydronium ions decreases.

a. increases
b. decreases
c. stays the same
d. a or b
e. a, b, or c

____ 8. The notation H3O+ (aq) is sometimes simplified to which of the following?
The notation H3O+ (aq) represents the hydronium ion, which is formed when a water molecule accepts a
proton (H⁺ ion). But in many cases chemists simplify chemical equations, and the hydronium ion is often
represented simply as H+ (aq), indicating the presence of a proton in the aqueous solution. This notation
emphasizes the acidic nature of the solution.

a. H2O (l)
b. H+ (aq)
c. H- (aq)
d. OH+ (aq)
e. OH- (aq)

____ 9. Which of these is present in all acid-base systems?

The correct answer is option d. a and b. In all acid-base systems, both hydronium ions (H3O+) and
hydroxide ions (OH-) are present. Hydronium ions are present in acidic solutions, while hydroxide ions are
present in basic solutions. So, both of these ions are essential components of acid-base systems.

a. hydronium ions
b. hydroxide ions
c. oxygen ions
d. a and b
e. a, b, and c

SCH4U Lesson Assignment Page 5

____ 10. Which is a hydronium ion?
A hydronium ion, H3O+, is a proton bonded to a water molecule by a covalent bond.

a. H3O+
b. H2O+
c. HCl
d. Cl+
e. OH-

____ 11. In which of the following reactions does NH3 act as Bronsted acid?
Option c. NH3 releases a proton (H+ ion). And Na and NH2 combine. Bronsted acid: An H+ ion is lost.

a.
NH3(aq) + HCl (aq) → NH4Cl (aq)
b.
NH3 (aq) + H+ (aq)→ NH4+ (aq)
c.
NH3 (aq) + Na (s) → NaNH2 (aq) + H2 (g)
d.
NH3 (aq) + H2O (l)→ NH4+ (aq) + OH- (aq
e. NH3(g) can never act as acid.

____ 12. Use the following information to answer the next question.
The carbonate ion is a polyatomic ion having empirical formula CO32–. Salts containing the
carbonate ion are of great use both industrially and mineralogically. The reaction that takes
place with water is shown below:
H2O( ) + CO32–(aq) → HCO3–(aq) + OH–(aq)

Which of the following statements about the above reaction is correct?

CO3^2- serves as the proton acceptor, resulting in the formation of the ion, HCO3–, which is the conjugate
acid of the base, CO3^2-

a. HCO3– (aq) is the conjugate acid of CO32–(aq)

b. HCO3– (aq) is the conjugate base of CO32–(aq)
c. CO32– (aq) is the conjugate acid of HCO32–(aq)
d. CO32–(aq) is the conjugate base of H2CO3 (aq)
e.
HCO3–(aq) is the conjugate acid of H2O( )

____ 13. Which is not included in the Arrhenius theory of acids and bases?
a base ionizes in water to form OH- ions, not H+ ions.

a. an acid contains H in the chemical formula

SCH4U Lesson Assignment Page 6

 b. a base contains OH in the chemical formula
c. an acid dissociates in water to form H3O+
d. a base ionizes in water to form OH-
e. a base dissociates in water to form H+

____ 14. Which of the following statements is correct?

Since HCl is a strong acid, it fully dissociates into H+ and Cl– ions. But the Cl– ion doesn’t readily accept a
proton in water, so it’s considered a weak conjugate base.

a. Cl–(aq) ion is a weak conjugate base of weak acid HCl(aq)

b. Cl–(aq) ion is a weak conjugate base of strong acid HCl(aq)
c. Cl–(aq) ion as a strong conjugate base of weak acid HCl(aq)
d. Cl–(aq) ion is a strong conjugate base of strong acid HCl(aq)
e. Cl–(aq) ion is a weak conjugate acid of strong base HCl(aq)

____ 15. Use the following information to answer the next question.
Hydrogen cyanide, HCN(l), is a pale blue, highly volatile liquid. It exists as gas above 26oC. It
reacts with water to form H3O+(aq) and CN–(aq).

Which of the following pairs are conjugate acid base pairs of the reaction of hydrogen cyanide, HCN(l) with
water?
HCN(l), is a pale blue, highly volatile liquid. It exists as gas above 26 C. It
o
reacts with water to form H3O (aq) and CN (aq).

a. HCN(aq) and /H3O+(aq)

b.
HCN(aq) and H2O( )
c. HCN(aq) and CN–(aq)
d. CN–(aq) and H3O+(aq)
e.
CN–(aq) and H2O( )

____ 16. Use the following information to answer the next question.
Carbonic acid, H2CO3(aq), is a chemical substance which plays an important
role in controlling the pH of body fluids. In aqueous solution it produces
HCO3–(aq) and CO32–(aq) as shown below:
H2CO3(aq) + H2O( ) → H3O+(aq) + HCO3–(aq)

HCO3–(aq) + H2O( ) → H3O+(aq) + CO32–(aq)

In the above equilibrium reactions, H2CO3(aq) is a(n)

In the given reactions, H2CO3 donates one proton to form HCO3- and then donates another proton to form
CO32-

a. strong acid
b. amphiprotic substance

SCH4U Lesson Assignment Page 7

 c. polyprotic acid
d. polyprotic base
e. strong base

____ 17. Use the following information to answer the next question.
Consider the dissociation of an acid in water as
HA(aq) + H2O( ) →H3O+(aq) + A–(aq)

Which of the following statements about the above ionization reaction is correct?
A higher value of Ka indicates a stronger acid because it corresponds to a higher concentration of
H3O+(aq) ions formed upon dissociation

a. The greater the value of the ionization constant, the higher the concentration of H3O+(aq)
and the stronger the acid.
b. The lower the value of the ionization constant, the higher the concentration of H3O+(aq)
and the stronger the acid.
c. The greater the value of the ionization constant, the lower the concentration of H3O+(aq)
and the weaker the acid.
d. The lower the value of the ionization constant, the lower the concentration of H3O+(aq)
and the stronger the acid.
e. There is no relationship between the ionization constant and the concentration of
H3O+(aq).

____ 18. Use the following information to answer the next question.
Consider the following reaction:
H2O(l) + NH3 (aq) → NH4+(aq) + OH– (aq)

Which of the following statements is correct at equilibrium?

the water molecule (H2O) behaves as an acid by donating a proton to ammonia (NH3), forming ammonium
ion (NH4+) and hydroxide ion (OH–). Since the hydrogen molecule is acting as an acid, the reverse
reaction is favored at equilibrium.

a. The products are favoured.

b. The reactants are favoured.
c. One of the reactants and one of the products are favoured.
d. The concentration of reactants and products are equal.
e. H2O(l) is a stronger acid than NH4+(aq).

____ 19. Use the following information to answer the next question.
The following reaction illustrates how the hydrogen carbonate ion,
HCO3–(aq), can behave as an acid:
HCO3–(aq) + NH3(aq) → NH4+(aq) + CO32–(aq)

In the reaction where the hydrogen carbonate ion is an acid, which of the following statements is correct at
equilibrium?

SCH4U Lesson Assignment Page 8

 In the given reaction, the hydrogen carbonate ion (HCO3–) behaves as an acid by donating a proton to
ammonia (NH3), forming ammonium ion (NH4+) and carbonate ion (CO32–). Since the hydrogen
carbonate ion is acting as an acid, the reverse reaction is favored at equilibrium.

a. Products are favoured.

b. Reactants are favoured.
c. One of the reactants and one of the products are favoured.
d. The concentration of reactants and products are equal.
e. HCO3–(aq) is a stronger acid than NH4+(aq).

SCH4U Lesson Assignment Page 9

____ 20. Use the following information to answer the next question.
Bicarbonate is an ion with the chemical formula HCO3–. In the presence
of water, it results in the following reactions:
(i) HCO3–(aq) + H2O(l) 🡪 H2CO3(aq) + OH–(aq)

(ii) HCO3–(aq) + H2O(l) 🡪 CO32–(aq) + H3O+(aq)

In the above reactions, the bicarbonate ion acts as _____.

In reaction (i), the bicarbonate ion (HCO3–) donates a proton (H+) to water to form carbonic acid (H2CO3)
and hydroxide ions (OH–). Therefore, in reaction (i), the bicarbonate ion acts as an acid.
In reaction (ii), the bicarbonate ion (HCO3–) accepts a proton (H+) from water to form carbonate ions
(CO32–) and hydronium ions (H3O+). Therefore, in reaction (ii), the bicarbonate ion acts as a base.

a. a strong acid
b. a strong base
c. an acid in reaction (i) and as a base in reaction (ii)
d. a base in reaction (i) and as an acid in reaction (ii)
e. a weak base

____ 21. A strong acid __________.

A strong acid ionizes almost completely in water. It breaks apart into ions very easily. This results in a high
concentration of hydrogen ions (H+) in the solution, making it highly acidic. So, strong acids have a strong
ability to release protons (H+) in water, which is why they ionize almost completely.

a. ionizes almost completely in water

b. has a low Ka value
c. has a strong conjugate base
d. a and b
e. a, b, and c

____ 22. Use the following information to answer the next question.
Consider the following reaction:
NH4+(aq) + H2O(l) → H3O+(aq) + NH3 (aq)

Which is true of NH4+(aq)?

NH4+(aq) acts as a proton donor, making it a Bronsted-Lowry acid.

a. It accepts a proton and is a Bronsted-Lowry base.

b. It donates a proton and is a Bronsted-Lowry base.
c. It accepts a proton and is a Bronsted-Lowry acid.
d. It donates a proton and is a Bronsted-Lowry acid.
e. It both accepts and donates a proton, and is therefore amphiprotic.

SCH4U Lesson Assignment Page 10

Part C ( Putting the Concepts to Work): Completion (40 marks): Using your reading, answer the following
questions. Give your answer as well as your strategy for determining your answer. As part of your answer, give
the page number (or website) that you used to find the answer the question.

1. (six marks) Hydrogen carbonate ion, HCO3–(aq), can react as follows:

→ H2CO3(aq) + Cl–(aq)

→ NH4+(aq) + CO32–(aq)

Classify hydrogen carbonate ion, HCO3–(aq), according to Bronsted-Lowry theory of acids and bases
.

An amphiprotic substance can react with both acids and bases. When reacting with an acid, it
acts as a base by accepting a proton. And when reacting with a base, it acts as an acid by
donating a proton.
The hydrogen carbonate ion (HCO3–(aq)) is an amphiprotic substance that can act as both an
acid and a base according to the Bronsted-Lowry theory.

2. (six marks) Use the following information to answer the next question.
The carbonate ion is a polyatomic ion having empirical formula CO32–. Salts containing the
carbonate ion are of great use both industrially and mineralogically. The reaction that takes
place with water is shown below:
H2O( ) + CO32–(aq) → HCO3–(aq) + OH–(aq)

Explain how you know the conjugated acid base pairs for this reaction.
H2O(l) + CO3^2-–(aq) → HCO3–(aq) + OH–(aq)
According to the Bronsted-Lowry theory of acids and bases, water (H2O) acts as an acid by donating a proton (H+) to the carbonate ion
(CO3^2–), which acts as a base by accepting the proton
. This proton transfer leads to the formation of bicarbonate ion (HCO3–) and hydroxide ion (OH–).
In this context, the acid, H2O, serves as the proton donor, resulting in the formation of the hydroxide ion (OH–), which is the conjugate base
of the acid, H2O. the base, CO3^2- acts as the proton acceptor, leading to the formation of the bicarbonate ion (HCO3–), which is the
conjugate acid of the base, CO3^2
the conjugate acid-base pairs in this reaction are:
[H2O (l), OH- (aq)] and [CO3^2- (aq), HCO3-(aq)]

SCH4U Lesson Assignment Page 11

3. (eight marks) The ionization of acetic acid is shown below:

CH3COOH(aq) + H2O( ) → H3O+(aq) + CH3COO–(aq)

Classify and describe the strength of CH3COOH(aq) and CH3COO–(aq) as a strong or weak acid, and as a
strong or weak base. Justify your reasoning.
CH3COOH as an acid:
(CH3COOH) is a weak acid. It only partially dissociates in water to form hydronium ions
(H3O+) and acetate ions (CH3COO–). This is because the equilibrium lies more towards the
reactants side, indicating incomplete dissociation. So, CH3COOH is classified as a weak acid.
CH3COO– as a base:
(CH3COO–) is the conjugate base of acetic acid. While it is a weak base, it has a slightly
greater tendency to accept a proton compared to other weak bases. However, it still does not
accept protons as effectively as strong bases. This is due to the equilibrium position favoring
the formation of undissociated CH3COOH. Therefore, CH3COO– is classified as a stronger,
but still weak base.

4. (eight marks) Consider the following equilibrium reaction in which the initial concentrations of all chemical
species are equal:
NH4+(aq) + CH3COO–(aq) →CH3COOH(aq) + NH3(aq)

Explain the direction of equilibrium, and state which substances will be in the highest concentration at
equilibrium.
Acetic acid (CH3COOH) is a stronger acid than ammonium ion (NH4+)
Acetate ion (CH3COO-) is a stronger base than ammonia (NH3)
Since acetic acid is a stronger acid than ammonium ion, it will have a greater tendency
to donate a proton. As a result, the equilibrium will lie to the left, favoring the
formation of the weaker acid and base pair (NH4+ and CH3COO-). Therefore, at
equilibrium, the concentrations of NH4+ and CH3COO- will be higher compared to the
concentrations of CH3COOH and NH3.

5. (three marks) If the pH of a solution is 2.00, what is the concentration of hydronium ions if the pH is
doubled?(show your work)

SCH4U Lesson Assignment Page 12

SCH4U Lesson Assignment Page 13
6. (three marks) Use the following information to answer the next question.
A solution is prepared by dissolving 4 g of sodium hydroxide,
NaOH(s), in enough water to make 1.0 L of solution.

What is the pH value of the solution? (Show your work)

3. (six marks) Use the following information to answer the next question.
A solution is prepared by dissolving 4 g of sodium hydroxide,
NaOH(s), in enough water to make 1.0 L of solution.

The pH value of the solution is ______.

(Show your work.)

SCH4U Lesson Assignment Page 14

SCH4U Lesson Assignment Page 15
SCH4U Lesson Assignment Page 16
SCH4U Lesson 18 Quiz
Answer Section

MATCHING

1. ANS: D PTS: 1 LOC: E2.1 TOP: 8.2

MSC: C
2. ANS: J PTS: 1 LOC: E2.1 TOP: 8.4
MSC: C
3. ANS: E PTS: 1 LOC: E2.1 TOP: 8.2
MSC: C
4. ANS: G PTS: 1 LOC: E2.1 TOP: 8.1
MSC: C
5. ANS: B PTS: 1 LOC: E2.1 TOP: 8.2
MSC: C
6. ANS: A PTS: 1 LOC: E2.1 TOP: 8.2
MSC: C
7. ANS: F PTS: 1 LOC: E2.1 TOP: 8.2
MSC: C
8. ANS: C PTS: 1 LOC: E2.1 TOP: 8.2
MSC: C
9. ANS: H PTS: 1 LOC: E2.1 TOP: 8.2
MSC: C
10. ANS: I PTS: 1 LOC: E2.1 TOP: 8.4
MSC: C

MULTIPLE CHOICE

1. ANS: C PTS: 1 LOC: E3.6 TOP: 8.1

MSC: K/U
2. ANS: C PTS: 1 LOC: E3.6 TOP: 8.1
MSC: K/U
3. ANS: C PTS: 1 LOC: E2.1 TOP: 8.1
MSC: K/U
4. ANS: C PTS: 1 LOC: E3.6 TOP: 8.1
MSC: K/U
5. ANS: A PTS: 1 LOC: E3.6 TOP: 8.1
MSC: K/U
6. ANS: D PTS: 1 LOC: E3.6 TOP: 8.1
MSC: K/U
7. ANS: B PTS: 1 LOC: E3.6 TOP: 8.1
MSC: K/U
8. ANS: B PTS: 1 LOC: E3.6 TOP: 8.1
MSC: K/U
9. ANS: D PTS: 1 LOC: E3.6 TOP: 8.1

SCH4U Lesson Assignment Page 17

 MSC: K/U
10. ANS: A PTS: 1 LOC: E3.6 TOP: 8.1
MSC: K/U
11. ANS: C PTS: 1 LOC: E3.6 TOP: 8.1
MSC: K/U
12. ANS: A PTS: 1 LOC: E3.6 TOP: 8.1
MSC: K/U
13. ANS: E PTS: 1 LOC: E3.6 TOP: 8.1
MSC: K/U
14. ANS: B PTS: 1 LOC: E3.7 TOP: 8.2
MSC: K/U
15. ANS: C PTS: 1 LOC: E3.6 TOP: 8.1
MSC: K/U
16. ANS: C PTS: 1 LOC: E3.6 TOP: 8.2
MSC: K/U
17. ANS: A PTS: 1 LOC: E3.7 TOP: 8.2
MSC: K/U
18. ANS: B PTS: 1 LOC: E3.6 TOP: 8.2
MSC: K/U
19. ANS: B PTS: 1 LOC: E3.6 TOP: 8.2
MSC: K/U
20. ANS: D PTS: 1 LOC: E3.6 TOP: 8.4
MSC: K/U
21. ANS: A PTS: 1 LOC: E3.7 TOP: 8.2
MSC: K/U
22. ANS: D PTS: 1 LOC: E3.6 TOP: 8.1
MSC: K/U

SHORT ANSWER

1. ANS:
According to the Bronsted-Lowry theory of acids and bases, substances capable of both donating a proton and
accepting a proton are amphiprotic substances. Hydrogen carbonate ion, HCO3–(aq) is an amphiprotic
substance.

PTS: 1 LOC: E3.6 TOP: 8.1 MSC: K/U

2. ANS:
The reaction of carbonate ion with water is given as

→ HCO3–(aq) + OH– (aq)

SCH4U Lesson Assignment Page 18

 On the left side of the equation, H2O( ) is a proton donor, therefore according to the Bronsted-Lowry theory,
it acts as an acid. CO32– (aq) ion is the proton acceptor, so it acts as a base. The acid, H2O( ), loses proton to
form OH–(aq), which is the conjugate base of acid H2O( ). The base, CO32–(aq), accepts a proton to form
HCO3–(aq), which is the conjugate acid of the base, CO32– (aq). So in the reaction, conjugated acid base pairs
are
H2O( )/OH–(aq) and CO32–(aq)/HCO3–(aq)

PTS: 1 LOC: E3.6 TOP: 8.1 MSC: K/U

3. ANS:
Acetic acid, CH3COOH(aq), only partially ionizes, and is therefore a weak acid. CH3COO–(aq) ion has a
slightly greater tendency to accept a proton. Therefore, CH3COO– (aq) ion is a stronger, but still weak base.

PTS: 1 LOC: E3.6 TOP: 8.2 MSC: K/U

4. ANS:
The reaction is given as:

→ +
In the above reaction, on the left side of the equation NH4+(aq) donates a proton and acts as an acid and
CH3COO–(aq) accepts a proton and acts as a base. While on the right hand side of the equation,
CH3COOH(aq) acts as an acid and NH3(aq) acts as a base. Comparing the reactive strengths of acids,
CH3COOH(aq) is a stronger acid than NH4+(aq) so the equilibrium will lie to the left and the concentration of
NH4+(aq) and CH3COO–(aq) will be higher at equilibrium.

PTS: 1 LOC: E3.6 | E3.7 TOP: 8.2 MSC: A

PROBLEM

1. ANS:
1.0 × 10–4.

Initial pH value of the solution = 2.00

Final pH value of the solution = 4.00
Let initial hydronium ion concentration be [H3O+].
Let final hydronium ion concentration be [H3O+]1
According to the question,
00 = –log [H3O+]
–log (1 × 10–2) = –log [H3O+]
[H3O+] = 10–2 mol/L ………(1)
4.00 = –log [H3O+]1
–log (1 × 10–4) = –log [H3O+]1
[H3O+]1 = 10–4 mol/L …………(2)
From (1) and (2) it is clear that the concentration of hydronium ion decreases from 1.0 × 10–2 to 1.0 × 10–4.

SCH4U Lesson Assignment Page 19

 PTS: 1 LOC: E2.4 TOP: 8.1 MSC: T/I
2. ANS:
13.0
Molar mass of NaOH = 40 g

Number of moles of NaOH(s) =

= = 0.1 mol NaOH(s)

Concentration of NaOH(aq) = =
= 0.1 mol/L

Since NaOH dissociates completely

Concentration of OH- ions = concentration of NaOH
= 0.1 mol/L
Or
[OH–] = 0.1 mol/L
pOH = – log [OH-]
= – log [0.1]
= 1.0
pH + pOH = 14.0
pH + 1 = 14.0
pH = 14.0 – 1.0 = 13.0
So pH of solution is 13.0

PTS: 1 LOC: E2.4 TOP: 8.3 MSC: T/I

3. ANS:
13.0
Molar mass of NaOH = 40 g

Number of moles of NaOH(s) =

= = 0.1 mol NaOH(s)

Concentration of NaOH(aq) = =
= 0.1 mol/L

Since NaOH dissociates completely

Concentration of OH- ions = concentration of NaOH
= 0.1 mol/L
Or
[OH–] = 0.1 mol/L
pOH = – log [OH-]

SCH4U Lesson Assignment Page 20

= – log [0.1]
= 1.0
pH + pOH = 14.0
pH + 1 = 14.0
pH = 14.0 – 1.0 = 13.0
So pH of solution is 13.0

PTS: 1 LOC: E2.4 TOP: 8.3 MSC: T/I

SCH4U Lesson Assignment Page 21