6^th Edition Kotz

Chapter 17

Principles of Reactivity:

Chemistry of Acids and Bases

Dr. Andrea Wallace

CGCC

Edited by

John Taylor

FCCJ-North Campus


Module Eleven: Acid/Base Equilibria Chapter 17	Possible	Actual
A. Idenification of Bronsted-Lowry acids&bases	10	Answer
B. Writing Equilibrium Constant Expressions	10	Answer
C Determination of Kw from Kc and Kh from Ka & Kw	10	Answer
D. Determination of pH & pOH from concentrations Problems	10	Answer
D. pH Sample 2		Answer
E. Determination of pH of weak acids/bases Problems	10	Answer
F. Hydrolysis Calculations	10	Answer
G. Common Ion Effect Problem	10	Answer
H. Discussion Questions Chapter 17	10	Answer
I. Determination of pH of polyprotic acids and/or Buffer Calculation Problem	10	Answer
J. Acid-Base Properties of Salts	10	Answer
K. Key Terms Chapter 17	10	Answer
M. Multiple choice Chapter 17 Kotz 5th	30	Answer
Old HCC Multiple Choice Applications -Chapter 17 from 1997
Module Eleven Total:	140

Chapter 17 Principles of Reactivity:
Chemistry of Acids and Bases

17.1 Acids, Bases, and the Equilibrium Concept, p. 798

Properties of Acids Properties of Bases

	Acid	Base
Arrhenius or Classical definition
Bronsted - Lowry definition
Lewis

Acids and bases can be weak or strong electrolytes depending on how much they ionize.

Strong electrolytes ionize ___________________.

Weak Electrolytes ionize ___________________.

(CD-Rom, Screen 17.5)

Consider the strong acid, HCl, hydrochloric acid.

Provide its ionization reaction: (Reaction with water.)

Consider the weak acid, CH₃CO₂H, acetic acid.

Provide its ionization reaction:

Provide its equilibrium expression: (K is sometimes referred to as the ionization constant, not just the equilibrium constant.)

Acids and bases that ionize extensively, with K>1, are referred to as strong acids or bases.

Acids and bases that do not ionize extensively, with K<1, are referred to as weak acids or bases.

17.2 Bronsted-Lowry Concept of Acids and Bases, p. 799

(CD-Rom, Screen 17.2)

ACIDS

Name	Formula	Mono, di, or triprotic	Weak/Strong
Hydrochloric acid	HCl
Hydrobromic acid	HBr
Hydroiodic acid	HI
Sulfuric acid	H₂SO₄
Nitric acid	HNO₃
Perchloric acid	HClO₄
Carbonic acid	H₂CO₃
Hydrofluoric acid	HF
Phosphoric acid	H₃PO₄
Phosphorus acid	H₃PO₃
Sulfurous acid	H₂SO₃
Hydrosulfuric acid	H₂S
Hydrocyanic acid	HCN
Acetic acid	CH₃CO₂H

Monoprotic Acid - ______________________________________________________

Diprotic Acid- _________________________________________________________

Triprotic Acid - ________________________________________________________

Polyprotic Acid - ______________________________________________________

Ionization Reactions for H₃PO₄

______________________________________________________________________

BASES

Name	Formula	Mono, di, or triprotic	Weak/Strong
Hydroxide ion	OH^-1
Ethoxide ion	CH₃CH₂O^-1
Amide ion	NH₂^-1
Hydride ion	H^-1
Sulfide ion	S^-2
Carbonate ion	CO₃^-2
Bicarbonate ion	HCO₃^-1
Sulfate ion	SO₄^-2
Phosphate ion	PO₄^-3
Hydrogen Sulfide ion	HS^-1
Cyanide ion	CN^-1
Acetate ion	CH₃CO₂^-1
Ammonia	NH₃

Monoprotic Base - ______________________________________________________

Diprotic Base- _________________________________________________________

Triprotic Base - ________________________________________________________

Polyprotic Base - ______________________________________________________

Ionization Reaction for NH₃

_____________________________________________________________________

Ionization Reactions for CO₃^-2

______________________________________________________________________

Amphiprotic - __________________________________________________________

Amphoteric - __________________________________________________________

Examples:

(Prove by showing ionization reactions.)

Conjugate Acid - _________________________

Conjugate Base - _________________________

Identify the acid, base, conjugate acid, and conjugate base in the following reactions.

HBr + NH₃ ó NH₄⁺¹ + Br^-1

HSO₃^-1 + H₂PO₄^-1 ó HPO₄^-2 + H₂SO₃

17.3 Water and the pH Scale, p. 802

(CD-Rom, Screen 17.3)

Water Autoionization and the Water Ionization Constant, K_w

2 H₂O_(l) ó H₃O⁺_(aq)+ OH^-_(aq)

K_w = =

where K_w is the __________ ____ for water.

Under neutral conditions, at 25 ^oC.

[H₃O⁺] =________________

[OH^-] = _________________

Under acidic conditions, at 25 ^oC.

[H₃O⁺] =________________

[OH^-] = _________________

Under basic conditions, at 25 ^oC.

[H₃O⁺] =________________

[OH^-] = _________________

Are the following solutions, acidic or basic?

1. [H₃O⁺] = 3.2 x 10^-11

2. [OH^-] = 2.1 x 10^-9

3. [OH^-] = 8.1 x 10^-3

Exercise 17.3, p. 805

A solution of the strong acid HCl has [HCl] = 4.0 x 10^-3 M. What are the concentrations of H₃O⁺ and OH^- in this solution?

pH Scale

(CD-Rom, Screen 17.4)

pH scale is another way to express _____________. It avoids using small numbers and exponential notation.

pH Scale

	Acidic	Neutral	Basic
pH
[H₃O⁺]

pOH Scale

	Basic	Neutral	Acidic
pOH
[OH^-]

Equations:

pH = -log [H₃O⁺]

pOH = -log [OH^-]

pH + pOH = 14

K_w = [H₃O⁺] [OH^-] = 1 x 10^-14

Two ways to determine pH

1) _______________________

2) _______________________

Exercise 17.4, p. 806

a) What is the pH of a 0.0012 M NaOH solution?

b) The pH of a diet soda is 4.32 at 25 ^oC. What are the hydronium and hydroxide ion concentrations in the soda?

c) If the pH of a solution of the strong base Sr(OH)₂ is 10.46, what is the concentration of Sr(OH)₂ in mol/L?

17.4 Equilibrium Constants for Acids and Bases, p. 806

(CD-Rom, Screen 17.6)

Strong Acids and Bases

For a strong acid, [H₃O⁺] in solution is equal to the original acid concentration. Similarly, for a strong base, [OH^-] equals the original base concentration.

Weak Acids and Bases

The strength of weak acids and bases is based on their ability to ___________________.

______________________are used to access their ability to _____________________.

HA_(aq) + H₂O_(l) ó H₃O⁺_(aq)+ A^-_(aq)

K_a = ___________________

where K_a is the _____________ constant or _____________ constant for an _________.

B_(aq) + H₂O_(l) ó BH⁺_(aq)+ OH^-_(aq)

K_b = ___________________

where K_b is the _____________ constant or _____________ constant for a _________.

The larger the K_a or K_b value the more the acid or base_____________ and the ________________ the acid or base.

See page 808, Table 17.3

List of acids and bases and their corresponding K_a and K_bvalues.

Note from the chart,

The stronger the acid, the _______________ the conjugate base.

The weaker the acid, the _______________ the conjugate base.

(Trend is also true for bases and their conjugate acids.)

Exercise 17.5, p. 810

Use Table 17.3 to answer the following questions.

a) Which is the stronger acid, H₂SO₄ and H₂SO₃?

b) Is benzoic acid, C₆H₅CO₂H, stronger or weaker than acetic acid?

c) Which has the stronger conjugate base, acetic acid or boric acid?

d) Which is the stronger base, ammonia or the acetate ion?

e) Which has the stronger conjugate acid, ammonia or the acetate ion?

Acid-Base Properties of Salts

(CD-Rom, Screen 17.11)

Salt - ionic compound formed from the reaction of an ________________________.

Examples:

________________occurs when a salt dissolves in water and causes changes in H₃O⁺ and OH^- concentrations.

(Many of the bases we already mentioned are found in the form of salts.)

Table 17.4 Acid-Base Properties of Ions in Aqueous Solution, p. 811

Neutral

Basic

Acidic

Anions

Cl^-1, Br^-1, I^-1, NO₃^-1, ClO₄^-1

CH₃CO₂^-1, HCO₃^-1,

CO₃^-2, S^-2, F^-1, CN^-1, PO₄^-3, HS^-1, NO₂^-1, SO₄^-2, HPO₄^-2, SO₃^-2, Cl0^-1

HSO₄^-1, H₂PO₄^-1, HSO₃^-1

Cations

Li⁺¹, Na⁺¹, K⁺¹, Mg⁺², Ca⁺², Ba⁺²

Al(H₂O)₅(OH)²⁺ and analogous ions

Al⁺³ or Al(H₂O)₆³⁺ NH₄⁺¹, Transition Metal Ions hydrated or not.

The acid-base strength of the salt depends on the combination of acidic and basic ions.

Exercise 17.16, page 812

For each salt below, predict whether the pH will be greater than, less than, or equal to 7.

a) KBr

b) NH₄NO₃

c) AlCl₃

d) Na₂HPO₄

A logarithmic Scale of Relative Acid Strength, pK_a

pKa is used in many cases to compare acid strength (used almost exclusively in organic).

pK_a = - log K_a

See examples on p. 813.

The pKa becomes smaller as the acid strength ________________.

Exercise 17.7, p. 813

a) What is the pKa value for benzoic acid, C₆H₅CO₂H?

b) Is chloroacetic acid (ClCH₂CO₂H), pK_a = 2.87, a stronger or weaker acid than benzoic acid?

c) What is the pK_a for the conjugate acid of ammonia? Is this acid stronger or weaker than acetic acid? (From text, pK_a of acetic acid is 4.74.)

Relating the Ionization Constants for an Acid and Its Conjugate Base

The connection:

K_a x K_b = K_w

Exercise 17.8, page 814

K_a for lactic acid, CH₃CHOHCO₂H, is 1.4 x 10^-4. What is the K_b for the conjugate base of this acid, CH₃CHOHCO₂^-1? (Write a shortened version of the ionization reactions for both.)

17.5 Equilibrium Constants and Acid-Base Reactions, p. 814

Predicting the Direction of Acid-Base Reactions using Equilibrium Constants

Equilibrium always lies to the side of the weaker acid.

Consider the ionizations of HCl and CH₃CO₂H. Add the double arrows. Where does the equilibrium lie?

HCl + H₂O

CH₃CO₂H + H₂O

(Use Table 17.3 on page 808, to make decisions.)

Exercise 17.9, page 816

a) Which is the stronger Bronsted acid, HCO₃^-1 or NH₄⁺¹? Which has the stronger conjugate base?

b) Is a reaction between HCO₃^- ions and NH₃, product- or reactant-favored?

HCO₃^-1 + NH₃ ó NH₄⁺¹ + CO₃^-2

Exercise 17.10, page 816

Write the equation for the possible reaction between acetic acid and sodium hydrogen sulfate, NaHSO₄. Does the equilibrium lie to the left or right?

17.6 Types of Acid-Base Reactions, p. 816

(CD-Rom, Screen 17.7)

Acid - Base Reactions

Combination	Type of Solution formed Assuming Equal Molar Concentrations are Mixed
Strong Acid + Strong Base
Strong Acid + Weak Base
Strong Base + Weak Acid
Weak Acid + Weak Base

See Table 17.5, p. 817

Examples:

Strong Acid/Strong Base

Strong Acid/Weak Base

Weak Acid/Strong Base

Weak Acid/Weak Base

Exercise 17.11, p. 818

(Assess products when making a decision.)

a) Equal molar quantities of HCl_(aq) and NaCN_(aq) are mixed. Is the resulting solution acidic, basic, or neutral?

b) Equal molar quantities of acetic acid and sodium sulfite, Na₂SO₃ are mixed is the resulting solution acidic, basic, or neutral?

17.7 Calculations with Equilibrium Constants, p. 818

Calculating K_afrom pH

Exercise 17.12, page 820

A solution prepared from 0.055 mol of butanoic acid dissolved in sufficient water to give 1.0 L of solution has a pH of 2.72. Determine K_a for butanoic acid. The acid ionizes at according to the balanced equation.

CH₃CH₂ CH₂CO₂H_(aq) + H₂O ó H₃O⁺¹ + CH₃CH₂ CH₂CO₂^-1_(aq)

CH₃CH₂ CH₂CO₂H	H₃O⁺¹	CH₃CH₂ CH₂CO₂^-1

To sometimes avoid a quadratic equation:

the approximation method may be applied when

[HA] > 100 K_a or [B] > 100 K_b

In these cases ionization of the acid or base will be less than 10%.

In the approximation method, X is assumed to be very small. Any X's that are being added or subtracted in the equilibrium constant expression are dropped from the equation.

Exercise 17.13, page 822

What are the equilibrium concentrations of acetic acid, the acetate ion, and hydronium ion for a 0.10 M solution of acetic acid (K_a = 1.8 x 10^-5)? What is the pH of the solution?

Ionization Reaction:

Equation for % Ionization

% ionization = (quantity of acid ionized / initial acid concentration) x 100

Calculate the % ionization for the previous problem.

Exercise 17.14, page 823

[HF] = 0.015 M, K_a of HF = 7.2 x 10^-4

Could the approximation short cut be used in this problem to find equilibrium concentrations?

What is the pH of a 0.025 M solution of ammonia, NH₃? (K_b of NH₃ is 1.8 x 10^-5)

Ionization Reaction:

What is the pH of the Solution after an Acid-Base Reaction?

Example 17.8, p. 825

What is the pH of the solution that results from mixing 25 mL of 0.016 M NH₃ and 25 mL of 0.016 M HCl?

Exercise 17.16, p. 826

Calculate the pH after mixing 15 mL of 0.12 M acetic acid with 15 mL of 0.12 M NaOH. What are the major species in solution at equilibrium (besides water) and what are their concentrations?

17.8 Polyprotic Acids and Bases, p. 826

In ionizations of polyprotic acids and bases, assume that the majority of the hydronium or hydroxide concentration is released in the _________________ionization and that this concentration is used throughout all calculations.

Exercise 17.17, page 828

What is the pH of a 0.10 M solution of oxalic acid, H₂C₂O₄? What are the concentration of H₃O⁺, HC₂O₄^-, and the oxalate ion, C₂O₄^-2?

Provide the two ionization reactions.

____________________________________________________ K_a1 = 5.9 x 10^-2

____________________________________________________ K_a2 = 6.4 x 10^-5

17.9 The Lewis Concept of Acids and Bases, p. 828

(CD-Rom, Screen 17.12, 13, & 14)

Lewis Acid - __________________________

Lewis Base - __________________________

Lewis Acid –Base Reaction

Example of Transition Metal Complexes

(See Figure 17.7, page 830)

[Cu(NH₃)₄]⁺²

Exercise 17.18, p. 832

Describe each of the following as a Lewis Acid or a Lewis Base

a) PH₃

b) BCl₃

c) H₂S

d) HS^-1

17.10 Molecular Structure, Bonding, and Acid-Base Behavior, p. 832

Increasing acid strength ---à

HF HCl HBr HI

pKa +3.14 -7 -9 -10

Bond Strength 565 432 366 299

in kJ/mol Decreasing Bond Strength ---à

HNO₂ HNO₃

----------Increasing Acid Strength-----à

HClO HClO₂ HClO₃ HClO₄

Why?

Inductive Effect - the more _____________ there are in the molecule, the more these _______________ atoms pull the electron density back into the molecule, allowing _______ to be released more easily.

Why is a H⁺ removed from acetic acid at -OH and not the -CH?

Exercise 17.19, p. 837

a) Which is the stronger acid, H₂SeO₄ or H₂SeO₃?

c) Which is the stronger acid, HOCl or HOBr?

d) The molecule whose structure is illustrated here is amphetamine, a stimulant. Is the compound a Bronsted Acid, a Lewis base, a Bronsted Base, or some combination of these?