Deck 16: Acid-Base Equilibria

Question 1

According to the Arrhenius concept, an acid is a substance that ________.

A)is capable of donating one or more H⁺
B)causes an increase in the concentration of H⁺ in aqueous solutions
C)can accept a pair of electrons to form a coordinate covalent bond
D)reacts with the solvent to form the cation formed by autoionization of that solvent
E)tastes bitter

Answer 1

causes an increase in the concentration of H⁺ in aqueous solutions

Question 2

Which one of the following is a Br∅nsted-Lowry base?

A)(CH₃)₃N
B)CH₃COOH
C)HF
D)HNO₂
E)none of the above

Answer 2

(CH₃)₃N

Question 3

The K_a of hypochlorous acid (HClO)is 3.0 × 10^-8 at 25 °C. What is the percent ionization of hypochlorous acid in a 0.015 M aqueous solution of HClO at 25 °C?

A)4.5 × 10^-8
B)14
C)2.1 × 10^-5
D)0.14
E)1.4 × 10^-3

Answer 3

0.14

Question 4

Of the following, ________ is a weak acid.

A)HF
B)HCl
C)HBr
D)HNO₃
E)HClO₄

Question 5

A substance that is capable of acting as both an acid and as a base is ________.

A)autosomal
B)conjugated
C)ambiprotic
D)saturated
E)miscible

Question 6

Of the following acids, ________ is a strong acid.

A)HNO₂
B)H₂CO₃
C)HNO₃
D)HClO
E)HF

Question 7

The molar concentration of hydroxide ion in pure water at 25 °C is ________.

A)1.00
B)0.00
C)1.0 × 10^-14
D)1.0 × 10^-7
E)7.00

Question 8

Classify the following compounds as weak acids (W)or strong acids (S): nitrous acid hydrochloric acid hydrofluoric acid

A)W W W
B)S S S
C)S W W
D)W S S
E)W S W

Question 9

Which one of the following is a Br∅nsted-Lowry acid?

A)(CH₃)₃NH⁺
B)CH₃COOH
C)HF
D)HNO₂
E)all of the above

Question 10

A Br∅nsted-Lowry acid is defined as a substance that ________.

A)increases K_a when placed in H₂O
B)decreases [H⁺] when placed in H₂O
C)increases [OH^-] when placed in H₂O
D)acts as a proton acceptor
E)acts as a proton donor

Question 11

Classify the following compounds as weak acids (W)or strong acids (S): benzoic acid nitric acid acetic acid

A)W W W
B)S S S
C)S W W
D)W S S
E)W S W

Question 12

Which one of the following is the weakest acid?

A)HF (K_a = 6.8 × 10^-4)
B)HClO (K_a = 3.0 × 10^-8)
C)HNO₂ (K_a = 4.5 × 10^-4)
D)HCN (K_a = 4.9 × 10^-10)
E)Acetic acid (K_a = 1.8 × 10^-5)

Question 13

The magnitude of K_w indicates that ________.

A)water autoionizes very slowly
B)water autoionizes very quickly
C)water autoionizes only to a very small extent
D)the autoionization of water is exothermic

Question 14

Classify the following compounds as weak acids (W)or strong acids (S): hydrocyanic acid hydrofluoric acid phenol

A)W W W
B)S S S
C)S W W
D)W S S
E)W S W

Question 15

Which one of the following statements regarding K_w is false?

A)pK_w is 14.00 at 25 °C.
B)The value of K_w is always 1.0 × 10^-14.
C)K_w changes with temperature.
D)The value of K_w shows that water is a weak acid.
E)K_w is known as the ion product of water.

Question 16

The hydride ion, H^-, is a stronger base than the hydroxide ion, OH^-. The product(s)of the reaction of hydride ion with water is/are ________.

A)H₃O⁺ (aq)
B)OH^- (aq) + H₂ (g)
C)OH^- (aq) + 2H⁺ (aq)
D)no reaction occurs
E)H₂O₂ (aq)

Question 17

Of the acids in the table below, ________ is the strongest acid.

A)HOAc
B)HCHO₂
C)HClO
D)HF
E)HOAc and HCHO₂

Question 18

Of the following acids, ________ is not a strong acid.

A)HNO₂
B)H₂SO₄
C)HNO₃
D)HClO₄
E)HCl

Question 19

The molar concentration of hydronium ion in pure water at 25 °C is ________.

A)0.00
B)1.0 × 10^-7
C)1.0 × 10^-14
D)1.00
E)7.00

Question 20

A Br∅nsted-Lowry base is defined as a substance that ________.

A)increases [H⁺] when placed in H₂O
B)decreases [H⁺] when placed in H₂O
C)increases [OH^-] when placed in H₂O
D)acts as a proton acceptor
E)acts as a proton donor

Question 21

Using the data in the table, which of the conjugate acids below is the weakest acid?

A)NH₄⁺
B)C₅H₅NH⁺
C)H₃NOH⁺
D)NH₃CH₃⁺
E)NH₄⁺ and NH₃CH₃⁺

Question 22

Using the data in the table, which of the conjugate acids below is the strongest acid?

A)HClO
B)HCO₃^-
C)H₂S
D)NH₃CH₃⁺
E)H₂S and HClO

Question 23

Ammonia is a ________.

A)weak acid
B)strong base
C)weak base
D)strong acid
E)salt

Question 24

Which of the following ions will act as a weak base in water?

A)OH^-
B)Cl^-
C)NO₃^-
D)ClO^-
E)None of the above will act as a weak base in water.

Question 25

Which of the following aqueous solutions has the lowest [OH^-]?

A)a solution with a pH of 3.0
B)a 1 × 10^-4 M solution of HNO₃
C)a solution with a pOH of 12.0
D)pure water
E)a 1 × 10^-3 M solution of NH₄Cl

Question 26

A- is a weak base. Which equilibrium corresponds to the equilibrium constant K_a for HA?

A)HA (aq) + H₂O (l) H₂A⁺ (aq) + OH^- (aq)
B)A^- (aq) + H₃O⁺ (aq) HA (aq) + H₂O (l)
C)HA (aq) + H₂O (l) H₃O⁺ (aq) + A^- (aq)
D)A^- (aq) + H₂O (l) HA (aq) + OH^- (aq)
E)A^- (aq) + OH^- (aq) HOA^2- (aq)

Question 27

Using the data in the table, which of the conjugate acids below is the weakest acid?

A)HClO
B)HCO₃^-
C)H₂S
D)NH₃CH₃⁺
E)H₂S and HClO

Question 28

Using the data in the table, which of the conjugate bases below is the strongest base?

A)OAc^-
B)C₇H₅O₂^-
C)NO₂^-
D)F^-
E)OAc- and C₇H₅O₂^-

Question 29

A 0.0035 M aqueous solution of a particular compound has pH = 2.46. The compound is ________.

A)a weak base
B)a weak acid
C)a strong acid
D)a strong base
E)a salt

Question 30

Of the following substances, an aqueous solution of ________ will form basic solutions. NaHS Cu(NO₃)₂ KHCO₃ NaF

A)NaHS, Cu(NO₃)₂
B)KHCO₃, NaHS
C)NaF only
D)NaF, KHCO₃
E)NaHS, KHCO₃ and NaF

Question 31

Classify the following compounds as weak bases (W)or strong bases (S): methylamine carbonate ion potassium hydroxide

A)W W S
B)S S S
C)S W W
D)W S S
E)W S W

Question 32

HA is a weak acid. Which equilibrium corresponds to the equilibrium constant K_b for A^-?

A)HA (aq) + H₂O (l) H₂A⁺ (aq) + OH^-(aq)
B)A^- (aq) + H₃O⁺ (aq) HA (aq) + H₂O (l)
C)HA (aq) + OH^- (aq) H₂O (l) + H⁺ (aq)
D)A^- (aq) + H₂O (l) HA (aq) + OH^- (aq)
E)A^- (aq) + OH^- (aq) HOA^2- (aq)

Question 33

Classify the following compounds as weak bases (W)or strong bases (S): ammonia fluoride ion sodium hydroxide

A)W W S
B)S S S
C)S W W
D)W S S
E)W S W

Question 34

Using the data in the table, which of the conjugate acids below is the strongest acid?

A)NH₄⁺
B)C₅H₅NH⁺
C)H₃NOH⁺
D)NH₃CH₃⁺
E)NH₄⁺ and NH₃CH₃⁺

Question 35

Using the data in the table, which of the conjugate bases below is the weakest base?

A)OAc^-
B)C₇H₅O₂^-
C)NO₂^-
D)F^-
E)OAc^- and C₇H₅O₂^-

Question 36

Classify the following compounds as weak acids (W)or strong acids (S): hypochlorous acid perchloric acid chloric acid

A)W S S
B)S S S
C)S W W
D)W W W
E)W S W

Question 37

Which of the following ions will act as a weak base in water?

A)HS^-
B)F^-
C)NO₂^-
D)ClO^-
E)All of the above will act as a weak base in water.

Question 38

Using the data in the table, which of the conjugate bases below is the weakest base?

A)OAc^-
B)CHO₂^-
C)ClO^-
D)F^-
E)OAc^- and CHO₂^-

Question 39

Using the data in the table, which of the conjugate bases below is the strongest base?

A)OAc^-
B)CHO₂^-
C)ClO^-
D)F^-
E)OAc^- and CHO₂^-

Question 40

Which of the following aqueous solutions has the highest [OH^-]?

A)a solution with a pH of 3.0
B)a 1 × 10^-4 M solution of HNO₃
C)a solution with a pOH of 12.0
D)pure water
E)a 1 × 10^-3 M solution of NH₄Cl

Question 41

The conjugate acid of CH₃NH₂ is ________.

A)CH₃NH₂
B)CH₃NH₃⁺
C)CH₃NH₂⁺
D)CH₃NH⁺
E)none of the above

Question 42

Of the following, which is the strongest acid?

A)HClO
B)HClO₃
C)HClO₂
D)HClO₄
E)HIO

Question 43

What is the pH of an aqueous solution at 25.0 °C that contains 3.98 × 10^-9 M hydroxide ion?

A)8.40
B)5.60
C)9.00
D)3.98
E)7.00

Question 44

Which of the following acids will be the strongest?

A)H₂SO₄
B)HSO₄^-
C)H₂SO₃
D)H₂SeO₄
E)HSO₃^-

Question 45

Of the following substances, an aqueous solution of ________ will form basic solutions. NH₄Cl Cu(NO₃)₂ K₂CO₃ NaF

A)NH₄Cl, Cu(NO₃)₂
B)K₂CO₃, NH₄Cl
C)NaF only
D)NaF, K₂CO₃
E)NH₄Cl only

Question 46

The conjugate base of H₂PO₄^- is ________.

A)PO₄^3-
B)H₂PO₄
C)H₃PO₄
D)HPO₄^2-
E)none of the above

Question 47

The conjugate acid of HSO₄^- is ________.

A)SO₄^2-
B)H₂SO₄
C)HSO₄⁺
D)H⁺
E)HSO₃⁺

Question 48

What is the pOH of an aqueous solution at 25.0 °C that contains 3.98 × 10^-9 M hydroxide ion?

A)8.40
B)5.60
C)9.00
D)3.98
E)7.00

Question 49

Calculate the pOH of a solution at 25.0 °C that contains 1.94 × 10^-10 M hydronium ions.

A)1.94
B)4.29
C)7.00
D)14.0
E)9.71

Question 50

The conjugate base of HSO₄^- is ________.

A)OH^-
B)H₂SO₄
C)SO₄^2-
D)HSO₄⁺
E)H₃SO₄⁺

Question 51

In the gas phase reaction below, NH₃ is acting as a(n)________ base but not as a(n)________ base.

A)Arrhenius, Br∅nsted-Lowry
B)Br∅nsted-Lowry, Lewis
C)Lewis, Arrhenius
D)Lewis, Br∅nsted-Lowry
E)Arrhenius, Lewis

Question 52

Of the compounds below, a 0.1 M aqueous solution of ________ will have the highest pH.

A)KCN, K_a of HCN = 4.0 × 10^-10
B)NH₄NO₃, K_b of NH₃ = 1.8 × 10^-5
C)NaOAc, K_a of HOAc = 1.8 × 10^-5
D)NaClO, K_a of HClO = 3.2 × 10^-8
E)NaHS, K_b of HS^- = 1.8 × 10^-7

Question 53

Calculate the concentration (in M)of hydronium ions in a solution at 25.0 °C with a pOH of 4.223.

A)5.98 × 10^-5
B)1.67 × 10^-10
C)1.67 × 10⁴
D)5.99 × 10^-19
E)1.00 × 10^-7

Question 54

What is the pH of an aqueous solution at 25.0 °C that contains 3.98 × 10^-9 M hydronium ion?

A)8.400
B)5.600
C)9.000
D)3.980
E)7.000

Question 55

What is the pOH of an aqueous solution at 25.0 °C that contains 3.98 × 10^-9 M hydronium ion?

A)8.400
B)5.600
C)9.000
D)3.980
E)7.000

Question 56

A 0.1 M solution of ________ has a pH of 7.0.

A)Na₂S
B)KF
C)NaNO₃
D)NH₄Cl
E)NaF

Question 57

What is the conjugate base of OH^-?

A)O₂
B)O^-
C)H₂O
D)O^2-
E)H₃O⁺

Question 58

What is the conjugate acid of CO₃^2- ?

A)CO₂^2-
B)HCO₂^2-
C)H₂CO₃
D)HCO₃^-
E)none of the above

Question 59

Calculate the pH of a solution at 25.0 °C that contains 1.94 × 10^-10 M hydronium ions.

A)1.94
B)4.29
C)7.00
D)14.0
E)9.71

Question 60

What is the conjugate acid of NH₃?

A)NH₃
B)NH₂⁺
C)NH₃⁺
D)NH₄⁺
E)NH₄OH

Question 61

The K_a of acetic acid (HC₂H₃O₂)is 1.8 × 10^-5. What is the pH at 25.0 °C of an aqueous solution that is 0.100 M in acetic acid?

A)+2.87
B)-2.87
C)-11.13
D)+11.13
E)+6.61

Question 62

The pH of a 0.10 M solution of a weak base is 9.82. What is the K_b for this base?

A)2.1 × 10^-4
B)4.4 × 10^-8
C)8.8 × 10^-8
D)6.6 × 10^-4
E)2.0 × 10^-5

Question 63

The pH of a 0.30 M solution of a weak acid is 2.67. What is the K_a for this acid?

A)2.1 × 10^-4
B)4.4 × 10^-4
C)1.5 × 10^-4
D)6.6 × 10^-4
E)none of the above

Question 64

An aqueous solution contains 0.050 M of methylamine. The concentration of H⁺ in this solution is ________ M. K_b for methylamine is 4.4 × 10^-4.

A)0.050
B)2.2 × 10^-13
C)2.9 × 10^-13
D)4.5 × 10^-13
E)2.2 × 10^-12

Question 65

Z^- is a weak base. An aqueous solution of NaZ is prepared by dissolving 0.350 mol of NaZ in sufficient water to yield 1.0 L of solution. The pH of the solution was 8.93 at 25.0 °C. The K_b of Z^- is ________.

A)1.2 × 10^-5
B)6.9 × 10^-9
C)2.1 × 10^-10
D)9.9 × 10^-2
E)2.8 × 10^-12

Question 66

A 0.15 M aqueous solution of the weak acid HA at 25.0 °C has a pH of 5.35. The value of K_a for HA is ________.

A)3.0 × 10^-5
B)1.8 × 10^-5
C)7.1 × 10^-9
D)1.3 × 10^-10
E)3.3 × 10⁴

Question 67

HZ is a weak acid. An aqueous solution of HZ is prepared by dissolving 0.020 mol of HZ in sufficient water to yield 1.0 L of solution. The pH of the solution was 4.93 at 25.0 °C. The K_a of HZ is ________.

A)1.2 × 10^-5
B)6.9 × 10^-9
C)1.4 × 10^-10
D)9.9 × 10^-2
E)2.8 × 10^-12

Question 68

The pH of a 0.55 M aqueous solution ammonia, NH₃, at 25.0 °C is 11.50. What is the value of K_b for NH₃?

A)2.0 × 10^-9
B)1.1 × 10^-9
C)6.0 × 10^-5
D)1.8 × 10^-5
E)none of the above

Question 69

The pH of a 0.25 M aqueous solution of hydrofluoric acid, HF, at 25.0 °C is 2.03. What is the value of K_a for HF?

A)2.0 × 10^-9
B)1.1 × 10^-9
C)6.0 × 10^-5
D)3.5 × 10^-4
E)none of the above

Question 70

Determine the pH of a 0.35 M aqueous solution of CH₃NH₂ (methylamine). The K_b of methylamine is 4.4 × 10^-4.

A)10.00
B)3.86
C)12.09
D)1.96
E)13.24

Question 71

An aqueous solution contains 0.100 M NaOH at 25.0 °C. The pH of the solution is ________.

A)0.100
B)1.00
C)13.00
D)7.00
E)-1.00

Question 72

The acid-dissociation constants of phosphoric acid (H₃PO₄)are K_a1 = 7.5 × 10^-3, K_a2 = 6.2 × 10^-8, and K_a3 = 4.2 × 10^-13 at 25.0 °C. What is the pH of a 2.5 M aqueous solution of phosphoric acid?

A)1.82
B)0.40
C)2.51
D)0.86
E)0.13

Question 73

The acid-dissociation constants of sulfurous acid (H₂SO₃)are K_a1 = 1.7 × 10^-2 and K_a2 = 6.4 × 10^-8 at 25.0 °C. Calculate the pH of a 0.163 M aqueous solution of sulfurous acid.

A)4.53
B)1.28
C)1.86
D)6.21
E)1.93

Question 74

Calculate the concentration (in M)of hydroxide ions in a solution at 25.0 °C with a pOH of 4.223.

A)5.98 × 10^-5
B)1.67 × 10^-10
C)1.67 × 10⁴
D)5.99 × 10^-19
E)1.00 × 10^-7

Question 75

A 0.15 M aqueous solution of the weak base B at 25.0 °C has a pH of 8.88. The value of K_b for B is ________.

A)3.0 × 10^-5
B)1.8 × 10^-5
C)3.9 × 10^-10
D)1.3 × 10^-10
E)none of the above

Question 76

An aqueous solution contains 0.050 M of methylamine. The concentration of hydroxide ion in this solution is ________ M. K_b for methylamine is 4.4 × 10^-4.

A)0.050
B)2.2 × 10^-5
C)2.9 × 10^-3
D)4.5 × 10^-3
E)4.7 × 10^-3

Question 77

The pH of a 0.60 M aqueous solution of formic acid, HCHO₂, at 25.0 °C is 1.98. What is the value of K_a for formic acid?

A)2.0 × 10^-5
B)1.8 × 10^-4
C)6.0 × 10^-5
D)3.5 × 10^-4
E)none of the above

Question 78

An aqueous solution contains 0.150 M HCl at 25.0 °C. The pH of the solution is ________.

A)0.150
B)1.00
C)13.00
D)7.00
E)0.82

Question 79

The pH of a 0.55 M aqueous solution of hypobromous acid, HBrO, at 25.0 °C is 4.48. What is the value of K_a for HBrO?

A)2.0 × 10^-9
B)1.1 × 10^-9
C)6.0 × 10^-5
D)3.3 × 10^-5
E)3.0 × 10⁴

Question 80

The K_a of hypochlorous acid (HClO)is 3.00 × 10^-8. What is the pH at 25.0 °C of an aqueous solution that is 0.0200 M in HClO?

A)+2.45
B)-2.45
C)-9.22
D)+9.22
E)+4.61