Deck 16: Acid-Base Equilibria

Question 1

A BrØnsted- Lowry base is defined as a substance that .

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

Answer 1

acts as a proton acceptor

Question 2

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

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

Answer 2

W S S

Question 3

An aqueous solution contains 0.10 M NaOH. The solution is _.

A) highly colored
B) basic
C) acidic
D) very dilute
E) neutral

Answer 3

basic

Question 4

The base- dissociation constant of ethylamine (C₂H₅NH₂) is 6.4 × 10^{- 4} at 25.0 °C. The of [H⁺] in a 1.6 × 10^{- 2} M solution of ethylamine is M.

A) 3.2 × 10^{- 3}
B) 2.9 × 10^{- 3}
C) 11.46
D) 3.1 × 10^{- 12}
E) 3.5 × 10^{- 12}

Question 5

In which of the following aqueous solutions does the weak acid exhibit the highest percentage ionization?

A) 0.01 M HC₂H₃O₂ (K_a = 1.8 × 10^{- 5})
B) 0.01 M HClO (K_a = 3.0 × 10^{- 8})
C) 0.01 M HNO₂ (K_a = 4.5 × 10^{- 4})
D) 0.01 M HF (K_a = 6.8 × 10^{- 4})
E) These will all exhibit the same percentage ionization.

Question 6

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

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

Question 7

The acid- dissociation constant at 25.0 °C for hypochlorous acid (HClO) is 3.0 × 10^{- 8}. At equilibrium, the molarity of H₃O⁺ in a 0.010 M solution of HClO is .

A) 2.00
B) 0.010
C) 1.7 × 10^{- 5}
D) 5.8 × 10^{- 10}
E) 4.76

Question 8

A 0.1 M aqueous solution of will have a pH of 7.0 at 25.0 °C.

A) NaOCl
B) KCl
C) NH₄Cl
D) Ca(OAc)₂
E) KCl and NH₄Cl

Question 9

The concentration of water in pure water is approximately M.

A) 0.100
B) 83
C) 18
D) 55
E) 100

Question 10

Of the following acids, is not a strong acid.

A) H₂SO₄
B) HNO₂
C) HCl
D) HClO₄
E) HNO₃

Question 11

Which of the following acids will be the strongest?

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

Question 12

The K_a of hypochlorous acid (HClO) is 3.0 × 10^{- 8} at 25.0 °C. What is the % ionization of hypochlorous acid in a 0.015- M aqueous solution of HClO at 25.0 °C?

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

Question 13

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

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

Question 14

Which one of the following is a BrØnsted- Lowry acid?

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

Question 15

A 0.1 M solution of has a pH of 7.0.

A) NaF
B) NaNO₃
C) NH₄Cl
D) Na₂S
E) KF

Question 16

The magnitude of K_w indicates that .

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

Question 17

Calculate the molarity of hydroxide ion in an aqueous solution that has a pOH of 5.33.

A) 5.3 × 10^{- 14}
B) 2.1 × 10^{- 9}
C) 8.67
D) 4.7 × 10^{- 6}
E) 8.7 × 10^{- 14}

Question 18

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

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

Question 19

A BrØnsted- Lowry acid is defined as a substance that .

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

Question 20

Classify the following compounds as weak acids (W) or strong acids (S):

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

Question 21

Which one of the following is the weakest acid?

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

Question 22

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

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

Question 23

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

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

Question 24

An aqueous solution at 25.0 °C contains [H⁺] = 0.0990 M. What is the pH of the solution?

A) 1.00
B) 1.00× 10^{- 13}
C) - 1.00
D) 13.0
E) 0.0990

Question 25

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

Question 26

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

A) Lewis, BrØnsted- Lowry
B) Arrhenius, BrØnsted- Lowry
C) Arrhenius, Lewis
D) BrØnsted- Lowry, Lewis
E) Lewis, Arrhenius

Question 27

Which one of the following statements regarding K_w is false?

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

Question 28

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

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

Question 29

Ammonia is a .

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

Question 30

The pH of an aqueous solution at 25.0 °C is 10.66. What is the molarity of H⁺ in this solution?

A) 4.6 × 10^{- 4}
B) 3.3
C) 2.2 × 10^{- 11}
D) 1.1 × 10^{- 13}
E) 4.6 × 10¹⁰

Question 31

Of the following, which is the strongest acid?

A) HClO
B) HClO₂
C) HClO₃
D) HIO
E) HClO₄

Question 32

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

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

Question 33

Nitric acid is a strong acid. This means that .

A) HNO₃ cannot be neutralized by a weak base
B) HNO₃ produces a gaseous product when it is neutralized
C) HNO₃ does not dissociate at all when it is dissolved in water
D) aqueous solutions of HNO₃ contain equal concentrations of H⁺(aq) and OH^- (aq)
E) HNO₃ dissociates completely to H⁺(aq) and NO₃^- (aq) when it dissolves in water

Question 34

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

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

Question 35

Which solution below has the highest concentration of hydroxide ions?

A) pH = 7.93
B) pH = 3.21
C) pH = 7.00
D) pH = 12.6
E) pH = 9.82

Question 36

Of the following, is a weak acid.

A) HF
B) HClO₄
C) HCl
D) HBr
E) HNO₃

Question 37

An aqueous solution of _ will produce a basic solution.

A) NaHSO₄
B) KBr
C) Na₂SO₃
D) NaCl
E) NH₄ClO₄

Question 38

The acid- dissociation constant of hydrocyanic acid (HCN) at 25.0 °C is 4.9 × 10^{- 10}. What is the pH of an aqueous solution of 0.080 M sodium cyanide (NaCN)?

A) 11.11
B) 3.9 × 10^{- 11}
C) 1.3 × 10^{- 3}
D) 7.8 × 10^{- 12}
E) 2.89

Question 39

In basic solution, .

A) [H₃O⁺] > [OH^- ]
B) [H₃O⁺] < [OH^- ]
C) [H₃O⁺] = 0 M
D) [OH^- ] > 7.00
E) [H₃O⁺] = [OH^- ]

Question 40

Of the following, which is the strongest acid?

A) HIO₂
B) HIO
C) HIO₄
D) HIO₃
E) The acid strength of all of the above is the same.

Question 41

A solution of acetic acid is 2.0% dissociated at 25.0 ^oC. What was the original concentration ( in M) of the acetic acid solution? The K_a at 25.0 ^oC for acetic acid is 1.8 × 10^{- 5}.

Question 42

What is the concentration (in M) of hydroxide ions in a solution at 25.0 °C with pH = 4.282?

A) 5.22 × 10^{- 5}
B) 1.91 × 10^{- 10}
C) 9.72
D) 4.28
E) 1.66 × 10⁴

Question 43

What is the pH of a sodium formate solution prepared by adding 0.680 grams of sodium formate to 100.0 ml of water at 25.0 ^oC? The K_a at 25.0 ^oC for formic acid is 1.8 × 10^{- 4}.

Question 44

Determine the pH of a 0.15 M aqueous solution of KF. For hydrofluoric acid, K_a = 7.0 × 10^{- 4}.

A) 5.8
B) 6.6
C) 12
D) 8.2
E) 2.3

Question 45

K_a for HCN is 4.9 × 10^{- 10}. What is the pH of a 0.068 M aqueous solution of sodium cyanide?

A) 0.74
B) 2.9
C) 7.0
D) 13
E) 11

Question 46

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

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

Question 47

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

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

Question 48

A solution of formic acid is 3.0% dissociated at 25.0 ^oC. What is the original concentration (in M) of the formic acid solution? The K_a at 25.0 ^oC for formic acid is 1.8 × 10^{- 4}.

Question 49

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

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

Question 50

A 7.0 × 10^{- 3} M aqueous solution of Ca(OH)₂ at 25.0 °C has a pH of .

A) 1.4 × 10^{- 2}
B) 12.15
C) 7.1 × 10^{- 13}
D) 11.85
E) 1.85

Question 51

What is the conjugate acid of NH₃?

A) NH₃⁺
B) NH₄OH
C) NH₃
D) NH₄⁺
E) NH₂⁺

Question 52

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

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

Question 53

The K_a for HCN is 4.9 × 10^{- 10}. What is the value of K_b for CN^- ?

A) 4.9 × 10⁴
B) 2.0 × 10^{- 5}
C) 2.0 × 10⁹
D) 4.0 × 10^{- 6}
E) 4.9 × 10^{- 24}

Question 54

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

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

Question 55

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

A) 13
B) 12
C) 3.8
D) 10
E) 1.9

Question 56

The K_a of hydrofluoric acid (HF) at 25.0 °C is 6.8 × 10^{- 4}. What is the pH of a 0.35 M aqueous solution of HF?

A) 3.6
B) 3.2
C) 12
D) 0.46
E) 1.8

Question 57

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

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

Question 58

What is the pH of a sodium acetate solution prepared by adding 0.820 grams of sodium acetate to 100.0 ml of water at 25.0 ^oC? The K_a at 25.0 ^oC for acetic acid is 1.8 × 10^{- 5}.

Question 59

A solution of ammonia is 2.0% dissociated at 25.0 ^oC. What was the original concentration ( in M) of the ammonia solution? The K_b at 25.0 ^oC for ammonia is 1.8 × 10^{- 5}.

Question 60

Calculate the pOH of a 0.0827 M aqueous sodium cyanide solution at 25.0 °C. K_b for CN^- is 4.9 × 10^{- 10}.

A) 8.8
B) 9.3
C) 5.2
D) 1.1
E) 10

Question 61

What is the pH of an aqueous solution at 25.0 °C in which [H⁺] is 0.00250 M?

A) 3.40
B) 2.60
C) - 2.60
D) 2.25
E) - 3.40

Question 62

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

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

Question 63

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

A) 7.00
B) - 1.00
C) 1.00
D) 0.100
E) 13.0

Question 64

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) 0.13
B) 2.5
C) 0.40
D) 1.8
E) 0.87

Question 65

The acid- dissociation constant for chlorous acid, HClO₂, at 25.0 °C is 1.0 × 10^{- 2}. Calculate the concentration of H⁺ if the initial concentration of acid is 0.10 M.

A) 2.7 × 10^{- 2}
B) 3.2 × 10^{- 2}
C) 3.7 × 10^{- 2}
D) 1.0 × 10^{- 2}
E) 1.0 × 10^{- 3}

Question 66

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) 4.7 × 10^{- 3}
C) 2.2 × 10^{- 5}
D) - 4.9 × 10^{- 3}
E) 4.5 × 10^{- 3}

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

Question 68

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) 5.99 × 10^{- 19}
C) 1.00 × 10^{- 7}
D) 1.67 × 10⁴
E) 1.67 × 10^{- 10}

Question 69

The K_a of hydrazoic acid (HN₃) is 1.9 × 10^{- 5} at 25.0 °C. What is the pH of a 0.35 M aqueous solution of HN₃?

A) 5.2
B) 2.4
C) 11
D) - 2.4
E) 2.6

Question 70

What is the concentration (in M) of hydronium ions in a solution at 25.0 °C with pH = 4.282?

A) 1.66 × 10⁴
B) 9.71
C) 1.92 × 10^{- 10}
D) 5.22 × 10^{- 5}
E) 4.28

Question 71

The acid- dissociation constant, K_a, for gallic acid is 4.57 × 10^{- 3}. What is the base- dissociation constant, K_b, for the gallate ion?

A) 7.81 × 10^{- 6}
B) 5.43 × 10^{- 5}
C) 2.19 × 10^{- 12}
D) 2.19 × 10²
E) 4.57 × 10^{- 3}

Question 72

What is the pOH of a 0.0150 M solution of barium hydroxide?

A) 12.5
B) 1.52
C) 10.4
D) 1.82
E) 12.2

Question 73

What is the pH of a 0.0150 M aqueous solution of barium hydroxide?

A) 12.5
B) 1.52
C) 12.2
D) 1.82
E) 10.4

Question 74

K_a for HF is 7.0 × 10^{- 4}. K_b for the fluoride ion is _ _.

A) 7.0 × 10^{- 4}
B) 2.0 × 10^{- 8}
C) 1.4 × 10^{- 11}
D) 1.4 × 10³
E) 7.0 × 10^{- 18}

Question 75

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) 1.4
B) 7.2
C) 1.8
D) 1.3
E) 4.5

Question 76

The conjugate base of HSO₄^- is

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

Question 77

The K_a of hypochlorous acid (HClO) is 3.00 × 10^{- 8} at 25.0 °C. Calculate the pH of a 0.0385 M hypochlorous acid solution.

A) - 1.41
B) 7.52
C) 1.41
D) 8.94
E) 4.47

Question 78

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

A) 6.6 × 10^{- 4}
B) 2.0 × 10^{- 5}
C) 2.1 × 10^{- 4}
D) 4.3 × 10^{- 8}
E) 8.8 × 10^{- 8}

Question 79

K_b for NH₃ is 1.8 × 10^{- 5}. What is the pH of a 0.35 M aqueous solution of NH₄Cl at 25.0 °C?

A) 9.1
B) 4.3
C) 11
D) 9.7
E) 4.9

Question 80

What is the conjugate base of OH^- ?

A) H₂O
B) O^2-
C) O₂
D) O^-
E) H₃O⁺