Chemistry - A Molecular Science

Chapter 12 Acid-Base Chemistry

12.11

EXERCISES 1.

Distinguish between an Arrhenius,

a Brønsted, and a Lewis acid.

2. Define a Lewis acid and a Lewis base. 3. What is a salt? 4. What is a conjugate acid-base pair? 5.^

Use curved arrows to show the mechanisms of the following Lewis acid-base reactions. Identify the Lewis acid and the Lewis base. What is the hybridization of the boron before an

d after reaction (a)? What is the

hybridization of the carbons before and

after reaction b? Note that reaction

(b) is a two-step reaction like that shown in Figure 12.4. a)

BF

+ NH 3

→ 3

F^3

B-NH

3

b)

CO

+ H 2

O 2

→

H

CO 2

(^3)

6.^

Use curved arrows to show the mechanisms of the following Lewis acid-base reactions. Identify the Lewis acid and the Lewis base. What is the hybridization of the boron before an

d after reaction (a)? What is the

hybridization of the sulfurs before and

after reaction b? Note that reaction

(b) is a two-step reaction like that shown in Figure 12.4. a)

B(OH)

+ OH 3

1-^ →

B(OH)

1- 4

b)

SO

+ H 2

O 2

→

H

SO 2

(^3)
7.
The potential energy diagram below is
for following the acid-base reaction:
HA(aq) + B(aq)
→
A
1-(aq) + HB
1+
(aq)
a) Which is the stronger acid? b) Which is the stronger base? c) What is the magnitude of the
equilibrium constant for the reaction (K > 1 or K < 1)?
d) Draw a probable transition state
(Section 9.7).

8. What is the conjugate aci

d of each of the following?

a)

1-F

b)

OH

1-^

c)^

HSO

1- 3

d)

2- S

9.^

What is the conjugate base

of each of the following?

a)

HClO

b)

NH

1+ 4

c)

H^3

PO

(^4)
d)
HSO
1- 3
10.
CH
and CH 3
groups are said to be 2
electron donating
groups because they
place electron density on the atoms to wh
ich they are attached. Which is a
stronger base CH
NH 3
or NH 2
? Explain. 3
11.
Which is the stronger acid, formic acid or acetic acid? Which acid has the greater pK
? Explain your answers. Refer toa
Exercise 10 for information
about CH
groups. 3
H
O C
O
H
HC^3
O C
O
H
formicacid
aceticacid
12.
Which is the stronger base, NH
or NF 3
? Explain. 3
13.
List the following compounds in order of increasing acidity. (Recall that from Exercise 10 that CH
groups are electron donating.) 3
H-O-H
H-O-Cl
H-O-CH
(^3)
H-O-I
14.
Indicate the stronger acid in each of
the following pairs and explain your
choice:
a)^
H
AsO 3
or H 4
AsO 3
(^3)
b)
H
SeO 2
or H 4
SO 2
(^4)
c) CH
or NH 4
(see Table 9.1 on page 176) 3
15.
Indicate the stronger acid in each of
the following pairs and explain your
choice:
a)^
H
SeO 2
or HSeO 3
1- 3
HA + B
1-A

• HB
  1+
  Reaction Coordinate
  b)
  HIO
  or HIO 4
  2
  c) CH
  COOH or CF 3
  COOH 3
  ygrenE

16. Use curved arrows and Lewis structur
    es to indicate the mechanisms of the
    following acid-base reactions:
    a)
    HClO

• H 2
  O 2
  b) PO
  3- + HCN 4
  c) HC
  H 2
  O 3


• OH 2
  1-^

17. Use curved arrows and Lewis structur
    es to indicate the mechanisms of the
    following acid-base reactions.
    a)
    HF + S
    2-^
    b)
    NH

• HNO 3
  (^2)
  c)
  H^2
  SO


• C 3
  H 2
  O 3
  1-^2

18. Equal amounts of benzoic acid and sodium acetate are mixed. At equilibrium, the concentration of the benzoate ion is just slightly greater than that of the acetate ion. What can
    be concluded about the relative acid
    strengths of acetic acid and benzoic acid?


19. 
    

    Consider the reaction,
    HBrO

    
    

• CN
  1-^ U
  BrO
  1- + HCN K = 5
  a) Which is the weaker of the tw
  o acids in the above reaction?
  b)^
  Which is the weaker of the two bases in the above reaction?
  c)^
  Given that K = 0.08 for HBrO + ClO
  1-U^
  BrO
  1- + HClO predict where
  on the acid-base table should HB
  rO be placed, above HClO, between
  HClO and HCN, or below HCN?
  © by
  North
  Carolina
  State
  University