acids and bases · 2020. 10. 7. · acids and bases brønsted acids and bases (16.1) the acid-base...

ACIDS AND BASES

Acids and Bases■ Brønsted Acids and Bases (16.1)

■ The Acid-Base Properties of Water (16.2)

■ pH – A Measure of Acidity (16.3)

■ Strength of Acids and Bases (16.4)

■ Weak Acids and Acid Ionization Constants (16.5)

■ Weak Bases and Base Ionization Constants (16.6)

■ The Relationship Between Conjugate Acid-Base Ionization Constants (16.7)

■ Molecular Structure and the Strength of Acids (16.8)

■ Acid-Base Properties of Salts (16.9)

■ Acidic, Basic, and Amphoteric Oxides (16.10)

■ Lewis Acids and Bases (16.11)

General Chemistry I – Concepts■ Representations of matter (1.3-1.4)

■ Formula calculations and stoichiometry (3.6-3.9)

■ Strong and weak acids and bases, molar concentrations of solutions and solution stoichiometry (4.4-4.6)

■ Periodicity of the elements and descriptive chemistry (8.6)

■ Lewis dot structures and electronegativities (9.4 and 9.5)

■ Molecular shape and polarity (10.1 and 10.2)

16.1 Brønsted Acids and Bases■ What is an acid?

– Review: Arrhenius acids– Review: Brønsted acids

■ Review: Which definition is more encompassing?

■ Review: What does this mean on the particle level?

■ Review: What are weak versus strong acids?

p. 102-103 of LA book

16.1 Brønsted Acids and Bases■ What is a base?

– Review: Arrhenius bases– Review: Brønsted bases

■ Review: Which definition is more encompassing?

■ Review: What does this mean on the particle level?

■ Review: What are weak versus strong bases?


16.1 Brønsted Acids and Bases■ What is a conjugate acid/base pair?

■ Review:

■ What is a better way to describe the hydrogen ion in water? H+ or H3O+


16.1 Brønsted Acids and Bases■ What is a conjugate acid/base pair?

■ Practice:

■ What is the conjugate acid of ammonia?

■ What is the conjugate base of acetic acid?

p. 105 of LA book

16.2 The Acid-Base Properties of Water■ What is the conjugate acid of water?

■ What is the conjugate base of water?

■ What the definition of amphoteric?

■ How is this equilibrium represented symbolically?


+2 2 3H O l H O l H O aq OH aq +2H O l H aq OH aq

Figure 16.1 p. 549

16.2 The Acid-Base Properties of Water■ How is this equilibrium represented in an equilibrium expression?

■ What is the value of the equilibrium constant (at 25oC)?

■ What does this tell us about the concentration of the:– Hydrogen ion– Hydroxide ion

p. 106 of LA book

16.2 The Acid-Base Properties of Water■ Ion-product constant (of water), Kw:

– The product of the molar concentrations of H+ and OH- ions at a particular temperature

■ What is the equilibrium expression and what is true when the solution is neutral?

■ What does this tell us about the concentration of the:– Hydrogen ion

■ In acidic solution

■ In basic solution

– Hydroxide ion■ In acidic solution

■ In basic solution


16.2 The Acid-Base Properties of Water■ Ion-product constant (of water), Kw

Solution [H+] [OH-] Acidic, basic or neutral

1 10-7 M

2 10-5 M

3 10-9 M

o 1425 H OH 1.0 10wK C

p. 107 of LA book

+2H O l H aq OH aq



1 10-7 M 10-7 M neutral

2 10-5 M

3 10-9 M

o 1425 H OH 1.0 10wK C

p. 107 of LA book

+2H O l H aq OH aq



1 10-7 M 10-7 M neutral

2 10-5 M 10-9 M acidic

3 10-9 M

o 1425 H OH 1.0 10wK C

p. 107 of LA book

+2H O l H aq OH aq



1 10-7 M 10-7 M neutral

2 10-5 M 10-9 M acidic

3 10-9 M 10-5 M basic

o 1425 H OH 1.0 10wK C

p. 107 of LA book

+2H O l H aq OH aq

16.2 The Acid-Base Properties of Water

■ What is present in an acidic solution?

■ What is present in a basic solution?


1 10-7 M 10-7 M neutral

2 10-5 M 10-9 M acidic

3 10-9 M 10-5 M basic

p. 107 of LA book

16.2 The Acid-Base Properties of Water■ Acidic solution

Solution [HCl] [H+] [OH-] Strength?

1 0.01 M

2 0.001 M

3 0.0001 M

+2 3HCl aq H O l H O aq Cl aq +HCl aq H aq Cl aq

o+ 142 ,25H O l H aq OH aq 1.0 10w CK

p. 108 of LA book



1 0.01 M 0.01 M

2 0.001 M 0.001 M

3 0.0001 M 0.0001 M


o+ 142 ,25H O l H aq OH aq 1.0 10w CK

p. 108 of LA book



1 0.01 M 0.01 M 10-12 M

2 0.001 M 0.001 M 10-11 M

3 0.0001 M 0.0001 M 10-10 M


o+ 142 ,25H O l H aq OH aq 1.0 10w CK

p. 108 of LA book



1 0.01 M 0.01 M 10-12 M strongest

2 0.001 M 0.001 M 10-11 M

3 0.0001 M 0.0001 M 10-10 M weakest


o+ 142 ,25H O l H aq OH aq 1.0 10w CK

p. 108 of LA book

16.2 The Acid-Base Properties of Water■ Basic solution

Solution [NaOH]0 [OH-] [H+] Strength?

1 0.01 M

2 0.001 M

3 0.0001 M

+NaOH aq Na aq OH aq o+ 142 ,25H O l H aq OH aq 1.0 10w CK




1 0.01 M 0.01 M

2 0.001 M 0.001 M

3 0.0001 M 0.0001 M





1 0.01 M 0.01 M 10-12 M

2 0.001 M 0.001 M 10-11 M

3 0.0001 M 0.0001 M 10-10 M





1 0.01 M 0.01 M 10-12 M strongest

2 0.001 M 0.001 M 10-11 M

3 0.0001 M 0.0001 M 10-10 M weakest



16.2 The Acid-Base Properties of Water■ What is the trend of

– acid strength (acidity) and the concentration of the hydrogen ion?– basic strength (basicity) and the concentration of the hydroxide ion?– acid strength (acidity) and the concentration of the hydroxide ion?

p. 109 of LA book

0

0.002

0.004

0.006

0.008

0.01

Conc

entr

atio

n /

M

Acidity

16.3 pH – A Measure of AcidityAcid strength and [H+]

Acid strength increasing

p. 110 of LA book

16.3 pH – A Measure of AcidityAcid strength and [OH-]

0

0.002

0.004

0.006

0.008

0.01

Conc

entr

atio

n /

M

Acidity

Acid strength increasing

p. 110 of LA book

16.2 The Acid-Base Properties of Water■ What if we wanted to consider the acidity of two very weak acids:

– [H+] = 10-4 M– [H+] = 10-6 M

p. 110 of LA book

0

0.002

0.004

0.006

0.008

0.01

Conc

entr

atio

n /

M

Acidity

16.3 pH – A Measure of AcidityWhat is we plotted this on a log scale instead?

First consider the data for an acidic solution

[H+] [OH-] log[H+] -log [H+] Acidity

0.01 M

0.001 M

0.0001 M

10-5 M

10-6 M

10-7 M

p. 111 of LA book




0.01 M Strong

0.001 M

0.0001 M

10-5 M

10-6 M Weak

10-7 M neutral

p. 111 of LA book




0.01 M 10-12 M Strong

0.001 M 10-11 M

0.0001 M 10-10 M

10-5 M 10-9 M

10-6 M 10-8 M Weak

10-7 M 10-7 M neutral

p. 111 of LA book




0.01 M 10-12 M -2 Strong

0.001 M 10-11 M -3

0.0001 M 10-10 M -4

10-5 M 10-9 M -5

10-6 M 10-8 M -6 Weak

10-7 M 10-7 M -7 neutral

p. 111 of LA book




0.01 M 10-12 M -2 2 Strong

0.001 M 10-11 M -3 3

0.0001 M 10-10 M -4 4

10-5 M 10-9 M -5 5

10-6 M 10-8 M -6 6 Weak

10-7 M 10-7 M -7 7 neutral

p. 111 of LA book


0.0

2.0

4.0

6.0

8.0

10.0

12.0

14.0

-log

[H+

]

Acidity

Acid strength decreasing

p. 111 of LA book


First consider the data for a basic solution

[OH-] [H+] log[H+] -log[H+] Basicity

0.01 M

0.001 M

0.0001 M

10-5 M

10-6 M

10-7 M

p. 111 of LA book




0.01 M Strong

0.001 M

0.0001 M

10-5 M

10-6 M Weak

10-7 M neutral

p. 111 of LA book




0.01 M 10-12 M Strong

0.001 M 10-11 M

0.0001 M 10-10 M

10-5 M 10-9 M

10-6 M 10-8 M Weak

10-7 M 10-7 M neutral

p. 111 of LA book




0.01 M 10-12 M -12 Strong

0.001 M 10-11 M -11

0.0001 M 10-10 M -10

10-5 M 10-9 M -9

10-6 M 10-8 M -8 Weak

10-7 M 10-7 M -7 neutral

p. 111 of LA book




0.01 M 10-12 M -12 12 Strong

0.001 M 10-11 M -11 11

0.0001 M 10-10 M -10 10

10-5 M 10-9 M -9 9

10-6 M 10-8 M -8 8 Weak

10-7 M 10-7 M -7 7 neutral

p. 111 of LA book


0.0

2.0

4.0

6.0

8.0

10.0

12.0

14.0

log

[H+

]

Basicity

Base strength increasing

p. 112 of LA book

16.3 pH – A Measure of Acidity■ What is pH

– algorithmically?– as a measure of acid strength?

Type of solution [H+] vs. [OH-] [H+] [OH-] pH

Acidic [H+] > [OH-] >10-7 M

16.3 pH – A Measure of Acidity■ What is pOH

– algorithmically?– as a measure of acid strength?

■ How are pH and pOH related?

p. 112 of LA book

Type of solution [H+] vs. [OH-] [OH-] pH pOH

Acidic [H+] > [OH-] 10-7 M

16.3 pH – A Measure of Acidity■ Let’s consider two acidic solutions:

– pH = 1.0– pH = 3.0

■ What is the ratio of water molecules to H+ in each solution (using 1 L)?

■ What do these look like?

■ Which solution is more acidic and by how much?

p. 113 of LA book

16.3 pH – A Measure of Acidity■ Practice:

■ What is the [H+] and pH of– 0.0015 M HNO3– 0.0015 M Ba(OH)2

p. 113 of LA book

16.4 Strength of Acids and Bases■ Review: What is a strong acid?

■ Review: What species are present for HCl?

■ What is the conjugate base of the strong acid, HCl?

Figure 16.3 p. 555

p. 113 of LA book

HCl aq H aq Cl aq

Concentration of HCl and H+ in solution

Conc

entr

atio

n /

M

0.01 M HCl (aq)In solution: 0.01 M H+

and 0.01 M Cl-

H+ / Cl-

HCl

16.4 Strength of Acids and Bases■ Review: What is a weak acid?

■ Review: What species are present for HF?

■ What is the conjugate base of the weak acid, HF?

Figure 16.3 p. 555

p. 114 of LA book

Concentration of HF and H+ in solution

Conc

entr

atio

n /

M

0.01 M HF (aq)In solution: 0.00734 M HF

and 0.00266 M H+

HF

H+

+HF aq H aq F aq

16.4 Strength of Acids and Bases■ Review: What is a strong acid?

■ Review: What is a weak acid?

■ What is the relative strength of the conjugate base of HCl?– What is the general trend of strong acids and their conjugate bases

■ What is the relative strength of the conjugate base of HF?– What is the general trend of weak acids and their conjugate bases

p. 114 of LA book

16.4 Strength of Acids and Bases

Table 16.2 p. 556

p. 115 of LA book

16.4 Strength of Acids and Bases■ What is the strongest acid that can exist in aqueous solution?

p. 115 of LA book

■ What does this mean for Table 16.2?

16.4 Strength of Acids and Bases■ For a 0.1 M solution of HCl vs. HF, which would you predict would have a

higher [H+] or pH?

■ For a 0.1 M solution of NaOH vs. NH3, which would you predict would have a higher [H+] or pH?

p. 115 of LA book

16.5 Weak Acids and Acid Ionization Constants■ Review: What is the equilibrium expression for the ionization of HF?

■ Review: What is the equilibrium expression for the ionization of any weak acid?

■ How does this equilibrium constant, Ka, tell us about acid strength?


Table 16.3 p. 559

16.5 Weak Acids and Acid Ionization Constants■ How does this equilibrium constant, Ka, tell us about acid strength?

■ Which solution will have a higher [H+]?– HF Ka = 7.1x10-4

– HNO2 Ka = 4.5x10-4

p. 119 of LA book


■ Which acid is a stronger weak acid?– HF Ka = 7.1x10-4

– HNO2 Ka = 4.5x10-4

■ How is the difference between these exemplified on the particle level?

p. 119 of LA book


■ What is the pH of 0.015 M:– HF Ka = 7.1x10-4

– HNO2 Ka = 4.5x10-4

■ When can you approximate and what is the 5% rule?



■ Percent ionization:– The ratio of ionized acid concentration at equilibrium over the initial

concentration of the acid

■ How does this tell us about acid strength?

■ Which solution would have a greater percent ionization?– 0.015 M HF Ka = 7.1x10-4

– 0.015 M HNO2 Ka = 4.5x10-4

p. 122 of LA book

16.5 Weak Acids and Acid Ionization Constants

How do [H+], pH and percent ionization vary for the same acid but decreasing concentrations?

HF [H+] pH Percent ionization

0.01 M

0.0015 M

0.001 M

0.00015 M

0.0001 M

0.000015 M

p. 122 of LA book




0.01 M 0.0081 M0.0015 M 0.0029 M0.001 M 0.0023 M

0.00015 M 0.00074 M0.0001 M 0.00056 M

0.000015 M 0.00013 M

p. 122 of LA book




0.01 M 0.0081 M 2.090.0015 M 0.0029 M 2.530.001 M 0.0023 M 2.63

0.00015 M 0.00074 M 3.130.0001 M 0.00056 M 3.25

0.000015 M 0.00013 M 3.90

p. 122 of LA book




0.01 M 0.0081 M 2.09 8.1%0.0015 M 0.0029 M 2.53 19.5%0.001 M 0.0023 M 2.63 23.3%

0.00015 M 0.00074 M 3.13 49.1%0.0001 M 0.00056 M 3.25 55.9%

0.000015 M 0.00013 M 3.90 84.8%

p. 122 of LA book

16.5 Weak Acids and Acid Ionization Constants■ What happens to percent ionization

as concentration decreases?

■ Why is this only true for weak acids/bases?

Figure 16.4 p. 565

p. 122 of LA book

16.5 Weak Acids and Acid Ionization Constants■ What about acids with more than one acidic hydrogen?

– What do these acids look like?– How do we represent the equilibrium?– How do we write the equilibrium expressions?– What would you predict about the relative size of Ka1 versus Ka2 versus

Ka3?

p. 123 of LA book

Table 16.4 p. 563

16.5 Weak Acids and Acid Ionization Constants■ Practice:

■ What is the concentration of all species at equilibrium of a 1.0 M phosphoric acid solution?

■ What is the order of the highest concentration to lowest concentration of all species in 1.0 L of solution?

p. 124 of LA book

16.6 Weak Bases and Base Ionization Constants■ Review: What is a strong base?

■ Review: What is a weak base?– How do we represent this symbolically?

■ Review: What does this look like on a particle level for NH3?

p. 125 of LA book

16.6 Weak Bases and Base Ionization Constants■ Review: What is the equilibrium expression for the ionization of NH3?

■ Review: What is the equilibrium expression for the ionization of any weak base?

■ How does this equilibrium constant, Kb, tell us about base strength?

p. 125 of LA book

Table 16.5 p. 570

16.6 Weak Bases and Base Ionization Constants■ How does this equilibrium constant, Kb, tell us about base strength?

■ Which solution will have a higher [OH-]?– NH3 Kb = 1.8x10-5

– CH3NH2 Kb = 4.4x10-4

p. 125 of LA book


■ Which is a stronger weak base?– NH3 Kb = 1.8x10-5

– CH3NH2 Kb = 4.4x10-4

■ How is the difference between these exemplified on the particle level?



■ What is the pH of 0.015 M:– NH3 Kb = 1.8x10-5

– CH3NH2 Kb = 4.4x10-4



■ Percent ionization:– The ratio of ionized base concentration at equilibrium over the initial

concentration of the base

■ Which solution would have a greater percent ionization?– 0.015 M NH3 Kb = 1.8x10-5

– 0.015 M CH3NH2 Kb = 4.4x10-4

■ How does this tell us about base strength?


■ Review: What is the conjugate base of HF?

■ What is the equilibrium expression for the reaction of HF in water?

■ What is the equilibrium expression for the reaction of F- in water?

p. 129 of LA book

16.7 The Relationship Between Conjugate Acid-Base Ionization Constants

■ Review: What are the rules for multiple reactions and the equilibrium constants?

■ How is Ka related to Kb?

■ What is the value of Kb of the fluoride ion?

■ What does Ka > Kb mean?

■ What does Ka < Kb mean?



Practice:

■ What is Kb for the acids listed below?– HNO2– HCN

■ Which acid is the strongest?

■ Which conjugate base is the strongest?

p. 130 of LA book


Table 16.3 p. 559

16.8 Molecular Structure and the Strength of Acids■ Review: What do we learn from a Lewis dot structure?

– How does bond enthalpy and electronegativity contribute to the strength of acid?

■ What about HCl versus HBr?

Table 16.6 p. 573


16.8 Molecular Structure and the Strength of Acids■ How can we verify this trend with experimental data?

■ (Can the solvent for the system be water?)

■ What does the equilibrium constant and equilibrium concentrations of HClversus HBr in acetic acid tell us about acid strength?


16.8 Molecular Structure and the Strength of Acids■ What are the Lewis dot structures of:

– HNO2 versus HNO3■ What are the rules for oxoacid strength?

– Which structure has a higher oxidation state of N?

■ HClO versus HClO2■ How the Lewis dot structures of the acids above relate oxoacid strengths?


16.9 Acid-Base Properties of Salts■ To work through these salts:

– Consider first what happens when the salt dissociates in water– Then consider the reaction of each ion with water (are either a conjugate

acid/base of a weak acid/base)– Then consider the production of the hydroxide ion or hydrogen ion

■ What happens when NaCl is put in water?

■ What is the pH of this solution?

p. 135 of LA book




■ What happens when NaF is put in water?


p. 136 of LA book




■ What happens when NH4Cl is put in water?


p. 136 of LA book




■ What happens when AlCl3 is put in water?


p. 136 of LA book

Figure 16.7 p. 579

p. 137 of LA book

16.9 Acid-Base Properties of Salts




■ What happens when NH4F is put in water?


p. 137 of LA book

Table 16.7 p. 580

p. 138 of LA book

16.9 Acid-Base Properties of Salts

16.10 Acidic, Basic and Amphoteric Oxides■ What are oxides?

■ What is the oxide of sodium?

■ What is the reaction of sodium oxide in water?– What is the pH of this solution?

■ What is the general rule of metal oxides?

p. 139 of LA book

16.10 Acidic, Basic and Amphoteric Oxides■ What is the reaction of dinitrogen pentoxide in water?

– What is the pH of this solution?

■ What is the general rule of nonmetal oxides?

■ What are amphoteric oxides?

■ What group of elements would you expect to be amphoteric oxides?

p. 139 of LA book

16.10 Acidic, Basic and Amphoteric Oxides

Figure 16.8 p. 582

p. 140 of LA book

• What type of element forms basic oxides?• What type of element forms acidic oxides?• What type of element forms amphoteric oxides?

16.11 Lewis Acids and Bases■ What is an acid?

– Review: Arrhenius acids– Review: Brønsted acids– Lewis acids

■ A substance that can accept a pair of electrons

■ What is a base?– Review: Arrhenius bases– Review: Brønsted bases– Lewis bases

■ A substance that can donate a pair of electrons

■ Which definition is the most encompassing?


16.11 Lewis Acids and Bases■ How do Lewis dot structure assist in assigning the Lewis acid or Lewis base

in a reaction?

■ Practice:

■ Carbon dioxide reacts with water. What is the Lewis acid and Lewis base in this reaction?

■ Can the ammonium ion be a Lewis base?

p. 141 of LA book

acids and bases · 2020. 10. 7. · acids and bases brønsted acids and bases (16.1) the acid-base...

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