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Ch. 16 Kimball Spring 2019
Discussion Worksheet - Chapter 16
Acid-Base Equilibria
Dr Cabirac Lecture
1. Identify the acid-base conjugate pairs in each of the following reactions:
A. CH3COO- + HCN ⇋ CH3OOH + CN-
B A CA CB
B. H2PO4- + NH3 ⇋ HPO42- + NH4+
A B CB CA
C. CO32- + H2O ⇋ HCO3- + OH-
B A CA CB
2. Complete the following table:
[H3O+]
[OH-]
pH
pOH
Acidic, Basic, or Neutral
2.3 x 10-5
4.3 x 10-10
4.6
9.4
acidic
1.3 x 10-9
7.7 x 10-6
8.9
5.1
basic
1.3 x 10-11
7.9 x 10-4
10.9
3.1
basic
3. Consider the following diagrams. (The hydrated proton is shown as a hydronium ion and water molecules are
omitted for clarity.)
A. Which diagram best represents a strong acid, such as HCl? b
B. Which represents a weak acid? c and d
C. Which represents a very weak acid? d
4. Calculate the pH for each of the following:
A. 0.054M HNO3 → H+ + NO3-
[H+] = 0.054M pH = -log[H+] = -log[0.054] = 1.27
B. 0.162M KOH →K+ + OH-
[OH-] = 0.162 M pOH = -log[OH-] = -log[0.162] = 0.79 pH = 14 – pOH = 14 – 0.79 = 13.21
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Ch. 16 Kimball Spring 2019
5. The pOH of a strong base solution is 1.88 at 25ºC. Calculate the concentration of the base if the base is:
A. KOH → K+ + OH-
pOH = 1.88
[OH-] = 10-pOH = 10-1.88 = 0.0132 M
[KOH] = [OH-] = 0.0132 M
B. Ba(OH)2 → Ba2+ + 2OH-
[OH-] = 10-pOH = 10-1.88 = 0.0132 M
[𝐵𝑎(𝑂𝐻)2]= [𝑂𝐻−](1 𝐵𝑎(𝑂𝐻)2
2 𝑂𝐻−) = 0.0132 𝑀 (1
2) = 𝟎.𝟎𝟎𝟔𝟔 𝑴
6. Which of the following statements is/are true for a 0.1 M solution of a weak acid HA?
A. the pH is 1.00
B. [H+] >> [A-]
C. [H+] = [A-]
D. the pH is less than 1
E. [H+] is less than 0.1 M
7. Which of the following has the highest pH?
A. 0.40 M HCOOH
B. 0.40 M HClO4
C 0.40 M CH3COOH
8. A. Calculate the percent ionization and pH of a 0.20 M of the monoprotic acetylsalicylic acid
(aspirin) for which Ka = 3.0 x 10-4.
% 𝒊𝒐𝒏𝒊𝒛𝒂𝒕𝒊𝒐𝒏 = 𝟑.𝟗%
pH = -log(0.0077) = 2.1
B. The pH of the gastric juice in the stomach is 1.00. Swallowing a certain amount
of aspirin results in a concentration of acetylsalicylic acid of 0.20 M. Calculate
the percent ionization and pH under these conditions.
% 𝒊𝒐𝒏𝒊𝒛𝒂𝒕𝒊𝒐𝒏 = 𝟎.𝟑𝟎%
pH = -log(𝟎.𝟏𝟎𝟎𝟔) = 0.9997 ≈ 1.0
9. Predict whether Na2HC6H5O7 forms an acidic solution or a basic solution when dissolved
in water. Ka > Kb so HC6H5O72- will behave as an acid Acidic
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Ch. 16 Kimball Spring 2019
10. Predict whether the following solutions are acidic, basic, or neutral:
A. KBr neutral
B. Cr(NO3)3acidic
C. NH4NO2acidic
D. K2SO3basic
11. In a certain experiment it is found that the pHs of 0.10 M solutions of three potassium
salts KX, KY, and KZ are 7.0, 9.0, and 11.0, respectively. Arrange the acids HX, HY,
and HZ in order of increasing acid strength.
HZ < HY < HX
12. Which would be considered a stronger Lewis acid?
A. BF3 or BCl3BF3
B. Fe2+ or Fe3+ F3+
13. The pH of an acid solution is 6.20, and the initial acid concentration is 0.010 M.
Calculate the Ka for this acid.
𝐾𝑎= 𝟑.𝟗𝟕 𝒙 𝟏𝟎−𝟏𝟏
14. A 0.0560 g quantity of acetic acid is dissolved in enough water to make 50.0 mL of
solution. Calculate the concentrations of H+, CH3COO-, and CH3COOH at equilibrium.
0.0560 𝑔 CH3COOH(1 𝑚𝑜𝑙
60.5 𝑔) = 9.33 𝑥 10−4 𝑚𝑜𝑙CH3COOH
0.0500L = 0.0187 𝑀 CH3COOH
x = 5.8 x 10-4 M = [H+] = [CH3COO-]
[CH3COOH] = 0.0187 - 5.8 x 10-4 = 0.0181 M
15. How many milliliters of a strong monoprotic acid solution at pH = 4.12 must be added to
528 mL of the same acid solution at pH = 5.76 to change its pH to 5.34? Assume the
volumes are additive. x = 0.021 L = 21 mL
Name
Formula
Kor
Ka Ko
‘Aceticacid
‘HCOOH
(or
HCHO)
18108
Arsenic
acid
HyAs0,
56x?
LOx107
3.0.x
10°
Arsenous
acid
HAs
5.1.x
10%
Ascotbicacid
HiCHAO6
BOX
TOS
1.6
x
107
Benzoic
acid
CH\COOH
(or
HC7H,0,)
63
x10
Boric acid
HBO,
ss
x10
Butanoicacid
C)H;COOH
(or
HCHO.)
1.5
x10°
‘Carbonic
acid
HCO,
43107
56x10"
Chloroacetic
acid
CH:CICOOH
(or
HE3H0;C)
14 x107
Chlorousacid
HCIOs
1x
10?
Citric
acid
HOOCC(OH)
(CH,COOH)2
(or
HyCaHs0;)
7AxW4
17
x105
4.0%
107
Cyanic
acid
HNO
35 x
104
Formicacid
HCOOH
(or
HCHO)
1.8
x
104
Hydroazoic
acid
HNs
1.910%
Hydrocyanic
acid
HEN
49
«10°
Hydrofluoricacid
HE
68
104
Hydrogen
chromate
ion
HCroy
3.0
x107
Hydrogen
peroxide
1.0,
24
x
108
Hydrogen
selenate
ion
HscOp
22
107
Hydrogen
sulfide
Hs
osx
1x10?
Hypobromous
acid
HBO
25
x10"
Hypochlorous
acid
HCI
3.0
x10°
Hypoiodousacid
HI
23x10
lodic
acid
Ho,
17
x10"
Lactic acid
(CH,CH(OH)COOH
(or
HCHO),
14x
104
‘Malonic
acid
CH:(COOH):
(oF
HCsH200)
1x1
20x
10%
Nitrous
acid
HNO,
45
x104
Onalicacid
(COOH);
(or
H:CE30)
59x?
64x10
Paraperiodic
acid
Hal0,
28x10% 53x10?
Phenol
CH&OH
(or
HCHO)
1.3.x
10
Phosphoricacia
HPO,
75x
62x10%
42x
10-9
Propionic
acid
CAHsCOOH (or
HCHO)
1.3108
Pyrophosphoric
acid
HPO;
30x10?
44x
10%
2.1107
Selenousacid
H,Se0,
Daw
84%
10%
Sulfuric
acid
FSO,
Steongacid
1.2
102
Sulfurousacid
H,S0s
17x?
64x
10%
‘Tartaric
acid
HOOC(CHOH),COOH
(or
HCHO.)
1.0
x107
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Ch. 16 Kimball Spring 2019
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