Deck 17: Acid-Base Equilibria in Aqueous Solutions

Question 1

If the OH^- ion concentration in an aqueous solution at 25.0 °C is measured as 3.4 × 10^-3 M, what is the pH?

A)2.47
B)7.22
C)8.24
D)11.53
E)16.47

Answer 1

11.53

Question 2

The pH of a solution is measured to be 6.30. What are the values of [H₃O⁺] and [OH^-] for this solution?

A)[H₃O⁺] = 5.0 × 10^-7, [OH^-] = 2.0 × 10^-8
B)[H₃O⁺] = 6.3 × 10^-7, [OH^-] = 7.7 × 10^?8
C)[H₃O⁺] = 2.0 × 10⁶, [OH^-] = 5.0 × 10⁷
D)[H₃O⁺] = 2.0 × 10^-8, [OH^-] = 5.0 × 10^-7
E)[H₃O⁺] = 1.6 × 10^-1, [OH^?] = 1.3 × 10^-1

Answer 2

[H₃O⁺] = 5.0 × 10^-7, [OH^-] = 2.0 × 10^-8

Question 3

The pH of a solution is measured to be 10.40. What are the values of [H₃O⁺] and [OH^-] for this solution?

A)[H₃O⁺] = 4.0 × 10^-11, [OH^-] = 4.0 × 10³
B)[H₃O⁺] = 2.5 × 10^-4, [OH^-] = 4.0 × 10^-11
C)[H₃O⁺] = 1.0 × 10^-10, [OH^-] = 3.6 × 10^-4
D)[H₃O⁺] = 4.0 × 10^-11, [OH^-] = 2.5 × 10^-4
E)[H₃O⁺] = 9.6 × 10^-2, [OH^-] = 2.8 × 10^-1

Answer 3

[H₃O⁺] = 4.0 × 10^-11, [OH^-] = 2.5 × 10^-4

Question 4

If the OH^? ion concentration in an aqueous solution at 25.0 °C is 6.6 × 10^-4 M, what is the molarity of the H⁺ ion?

A)1.5 × 10^-1 M
B)1.5 × 10^-4 M
C)6.6 × 10^-10 M
D)1.5 × 10^-11 M
E)6.6 × 10^-11 M

Question 5

An aqueous solution at 25.0 °C has an H⁺ concentration of 4.0 × 10^-2 molar. What is the molarity of the OH^- ion ?

A)4.0 × 10^-2 M
B)4.0 × 10^-9 M
C)4.0 × 10^-12 M
D)2.5 × 10^-13 M
E)25.0 M

Question 6

What is the molarity of OH^- ions if the H⁺ ion concentration in an aqueous solution at 25.0 °C is 0.100 M?

A)0.100 M
B)1.00 × 10^-7 M
C)10 × 10^-12 M
D)1.00 × 10^-13 M
E)0 M

Question 7

If the H⁺ ion concentration in an aqueous solution at 25.0 °C has a value of 0.10 M, what is the pOH of the solution?

A)1.00
B)7.00
C)12.00
D)13.00
E)11.40

Question 8

If the OH^- ion concentration in an aqueous solution at 25.0 °C has a value of 0.100 M, what is the pH of the solution?

A)1.00
B)7.00
C)12.00
D)13.00
E)11.40

Question 9

If the H⁺ ion concentration in an aqueous solution at 25.0 °C has a value of 0.10 M, then what is the pH of the solution?

A)?1.00
B)0.100
C)1.00
D)6.90
E)13.00

Question 10

If the OH^- ion concentration in an aqueous solution at 25.0 °C has a value of 0.10 M, then what is the pOH of the solution?

A)-1.00
B)0.10
C)1.00
D)6.90
E)13.00

Question 11

If the OH^- ion concentration in an aqueous solution at 25.0 °C is 3.4 × 10^-3 M, then what is the molarity of the H⁺ ion?

A)2.9 × 10^-3 M
B)2.9 × 10^-12 M
C)3.4 × 10^-17 M
D)5.8 × 10^-9 M
E)6.6 × 10^-10 M

Question 12

If the H⁺ ion concentration in an aqueous solution at 25.0 °C is measured as 6.6 × 10^-4 M, what is the pH?

A)3.00
B)3.18
C)6.60
D)9.55
E)10.82

Question 13

Calculate the pH of a beer in which the hydrogen ion concentration is 3.9 × 10^-5 M.

A)4.41
B)3.90
C)10.11
D)5.03
E)9.61

Question 14

A scientist is testing a new cleaning chemical and measures the pH of the cleaner to be 10.70. What is the [H₃O⁺] for this cleaner?

A)2.0 × 10^-11 M
B)10.7 M
C)9.3 × 10^-10 M
D)1.03 M
E)5.0 × 10^-10 M

Question 15

The pH of urine is approximately 3.0. How many times greater is the [H₃O⁺] in urine than in orange juice, which has an approximate pH of 6.0?

A)100
B)3.0
C)1000
D)1.8
E)2

Question 16

The pH of a specific household cleaner is approximately 11.0. How many times greater is the [OH^-] in this cleaner than in an ammonia solution, which has an approximate pH of 8.0?

A)100
B)3.0
C)1000
D)1.8
E)8

Question 17

Calculate the pH of a mixture made by adding 50.0 mL of 0.20 M HCl(aq)to 150.0 mL of water at 25.0 °C.

A)0.70
B)1.00
C)1.18
D)1.30
E)13.00

Question 18

Calculate the pH of a mixture made by adding 50.0 mL of 0.016 M HNO₃(aq)to 150.0 mL of water at 25.0 °C.

A)1.80
B)2.40
C)1.40
D)2.10
E)11.6

Question 19

A mixture is made by adding 50.0 mL of 0.20 M NaOH(aq)to 50.0 mL of water. At 25.0 °C, what is its pH?

A)1.00
B)4.55
C)7.00
D)13.00
E)13.30

Question 20

A mixture is made by adding 25.0 mL of 0.10 M KOH(aq)to 25.0 mL of water. At 25.0 °C, what is its pH?

A)1.30
B)12.70
C)13.00
D)1.00
E)13.30

Question 21

Calculate the pH of a 0.020 M solution of Ca(OH)₂ whose temperature is 25.0 °C.

A)1.40
B)0.040
C)1.69
D)12.60
E)12.30

Question 22

Calculate the pH of a 0.0018 M solution of Mg(OH)₂ whose temperature is 25.0 °C.

A)2.44
B)2.74
C)11.00
D)11.25
E)11.55

Question 23

Calculate the pH of a 0.25 M solution of KOH whose temperature is 25.0 °C.

A)12.61
B)?0.60
C)0.60
D)0.25
E)13.40

Question 24

Calculate the pH of a 0.025 M solution of NaOH whose temperature is 25.0 °C.

A)0.60
B)1.60
C)1.30
D)12.39
E)13.39

Question 25

Given 0.01 M solutions of each of the following acids, which solution would have the lowest pH?

A)Hypoiodous acid (HOI), K_a = 2.3 × 10^-11
B)Hypobromous acid (HOBr), K_a = 2.5 × 10^-9
C)Lactic acid (HC₃H₅O₃), K_a = 1.3 × 10^-4
D)Chlorous acid (HClO₂), K_a = 1.1 × 10^-2
E)Boric acid (H₃BO₃), K_a = 5.9 × 10^-10

Question 26

Given 0.01 M solutions of each of the following bases, which solution would have the highest pH?

A)Aniline (C₆H₅NH₂), K_b = 3.9 × 10^-10
B)Dimethylamine ((CH₃)₂NH), K_b = 5.1 × 10^-4
C)Hydrazine (N₂H₄), K_b = 1.3 × 10^-6
D)Methylamine (CH₃NH₂), K_b = 4.4 × 10^-4
E)Pyridine (C₅H₅N), K_b = 1.7 × 10^-9

Question 27

Given 0.01 M solutions of each of the following acids, which solution would have the lowest pH?

A)Nitrous acid (HNO₂), pK_a = 3.34
B)Phenol (HC₆H₅O), pK_a = 9.89
C)Acetic acid (HC₂H₃O₂), pK_a = 4.74
D)Hydrofluoric acid (HF), pK_a = 3.46
E)Formic acid (HCHO₂), pK_a = 3.74

Question 28

Given 0.01 M solutions of each of the following bases, which solution would have the highest pH?

A)Aniline (C₆H₅NH₂), pK_b = 9.39
B)Hydrazine (N₂H₄), pK_b = 5.89
C)Hydroxylamine (HONH₂), pK_b = 7.96
D)Methylamine (CH₃NH₂), pK_b = 3.36
E)Butylamine (C₄H₉NH₂), pK_b = 3.23

Question 29

The ionization constant, K_a, for macnic acid is 5.0 × 10^-5. What is the pK_a of this acid?

A)2.00 × 10⁴
B)4.30
C)5.70
D)1.75 × 10^-1
E)10.70

Question 30

The ionization constant, K_a, for lactic acid is 1.38 × 10^-4. What is the pK_a of this acid?

A)7.25 × 10³
B)2.59
C)3.86
D)5.38
E)3.59

Question 31

A certain base has a pK_b value of 4.74. What is the K_b value for this base?

A)1.8 × 10^-5
B)5.5 × 10⁴
C)5.5 × 10^-10
D)6.7 × 10^-1
E)9.7 × 10^-1

Question 32

The ionization constant, K_a, for benzoic acid is 6.28 × 10^-5. What is the pK_a of this acid?

A)1.59 × 10⁴
B)4.20
C)4.45
D)5.64
E)9.80

Question 33

The ionization constant, K_b, for ammonia has a value of 1.76 × 10^-5. What is the pK_b of this base?

A)+3.24
B)-4.75
C)+4.75
D)-9.25
E)+9.25

Question 34

Hydrazine is a base, and the value of its constant, K_b, is 1.70 × 10^-6. What is the value of pK_b for this base?

A)+4.30
B)+5.77
C)-5.77
D)+8.23
E)-8.23

Question 35

Butanoic acid, HC₄H₇O₂, has a pK_a value = 4.82. What is the value of the ionization constant for butanoic acid?

A)8.08 × 10^-3
B)1.51 × 10^-5
C)4.82 × 10^-7
D)6.61 × 10^-10
E)1.24 × 10^-12

Question 36

Hypochlorous acid, HClO, has a pK_a value = 7.82. What is the value of the ionization constant for hypochlorous acid?

A)5.42 × 10^-4
B)3.31 × 10^-7
C)7.52 × 10^-7
D)1.51 × 10^-8
E)1.84 × 10^-11

Question 37

A 0.100 M solution of an acid, HA, has a pH = 2.00. What is the value of the ionization constant, K_a for this acid?

A)1.1 × 10^-2
B)1.1 × 10^-3
C)1.1 × 10^-4
D)1.0 × 10^-3
E)1.0 × 10^-4

Question 38

A 0.200 M solution of an acid, HA, has a pH = 3.50. What is the value of the ionization constant Ka for this acid?

A)3.2 × 10^-4
B)1.6 × 10^-3
C)6.1 × 10¹
D)5.0 × 10^-7
E)7.9 × 10^-4

Question 39

Formic acid, HCO₂H, has an ionization constant with the value: K_a = 1.76 × 10^?4. Calculate the value of pK_b for the formate ion, CO₂H^-, the conjugate base of formic acid.

A)3.75
B)5.35
C)8.65
D)10.25
E)12.24

Question 40

Benzoic acid, HC₇H₅O₂, has an ionization constant with the value: K_a = 6.4 × 10^-5. Calculate the value of pK_b for the benzoate ion, C₇H₅O₂^-, the conjugate base of benzoic acid.

A)4.19
B)4.35
C)9.65
D)9.81
E)13.46

Question 41

Toluic acid, HC₈H₇O₂, has an ionization constant with the value: K_a = 1.23 × 10^-5. Calculate the value of pK_b for the conjugate base of toluic acid.

A)3.91
B)5.00
C)7.00
D)8.23
E)9.09

Question 42

The K_a of hydrocyanic acid (HCN)is 4.9 × 10^-10. What is the K_b of CN^-?

A)4.9 × 10⁴
B)4.9 × 10^-10
C)9.1 × 10^-10
D)9.3
E)2.0 × 10^-5

Question 43

A 0.400 M solution of an acid, HQ, has a pH = 1.301. What is the value of the ionization constant, K_a, for this acid?

A)5.00 × 10^-2
B)1.25 × 10^-3
C)5.56 × 10^-3
D)6.25 × 10^-3
E)7.14 × 10^-3

Question 44

A 0.200 M solution of an acid has a pH = 1.000. What is the value of the ionization constant, K_a, for this acid?

A)0.200
B)0.0400
C)1.00 × 10^-3
D)1.00
E)1.00 × 10^-1

Question 45

A 0.300 M solution of an acid, HZ, has a pH = 1.301. What is the value of the ionization constant, K_a, for this acid?

A)1.67 × 10^-1
B)2.00 × 10^-1
C)1.00 × 10^-2
D)7.14 × 10^-3
E)8.33 × 10^-3

Question 46

A 0.200 M solution of a weak base in water has a pH = 10.40 at 25°C. Calculate the value of K_b for this base.

A)1.0 × 10^-5
B)3.2 × 10^-7
C)2.2 × 10^-5
D)4.0 × 10^-11
E)5.0 × 10^-5

Question 47

A 0.075 M solution of a weak base in water has a pH = 11.21 at 25°C. Calculate the value of K_b for this base.

A)1.6 × 10^-3
B)5.1 × 10^-22
C)2.2 × 10^-2
D)3.6 × 10^-5
E)6.2 × 10^-12

Question 48

Calculate the pH of a 0.14 M HNO₂ solution that is 5.7% ionized.

A)11.90
B)0.85
C)1.70
D)13.10
E)2.10

Question 49

Calculate the pH of a 0.80 M HOCN solution that is 5.00% ionized.

A)1.40
B)1.30
C)0.0969
D)0.523
E)12.7

Question 50

Calculate the pH of a 0.095 M weak acid solution that is 1.9% ionized.

A)3.74
B)0.744
C)2.74
D)1.72
E)1.02

Question 51

The pH of a 0.035 M weak acid solution is 3.30. What is the percent ionization for this acid?

A)1.4
B)3.3
C)1.1
D)0.05
E)3.5

Question 52

A 0.100 M solution of an acid, HA, has a pH = 2.00. What is the value of the ionization constant, K_a, for this acid?

A)1.1 × 10^-2
B)1.1 × 10^-3
C)1.1 × 10^-4
D)1.0 × 10^-3
E)1.0 × 10^-4

Question 53

The ionization constant, K_a, for benzoic acid, HC₇H₅O₂, is 6.28 × 10^-5. What is the pH of a 0.15 molar solution of this acid?

A)0.82
B)2.52
C)4.20
D)5.03
E)5.79

Question 54

The ionization constant, K_a, for acetic acid, HC₂H₃O₂, is 1.76 × 10^-5. What is the pH of a 0.0800 molar solution of this acid?

A)1.097
B)2.013
C)2.926
D)4.754
E)5.852

Question 55

What is the pH of a 1.00 molar solution of nitrous acid? The K_a for nitrous acid is 7.1 × 10^-4.

A)1.57
B)1.93
C)2.04
D)2.67
E)3.15

Question 56

The ionization constant, K_b, for the weak base trimethylamine, (CH₃)₃N, is 7.4 × 10^-5. What is the pH of a 0.040 molar solution of this base?

A)8.37
B)9.87
C)10.70
D)11.23
E)12.60

Question 57

The ionization constant, K_a, for dichloroacetic acid, HC₂HO₂Cl₂ , is 5.0 × 10^-2. What is the pH of a 0.15 molar solution of this acid?

A)1.06
B)1.19
C)1.30
D)1.56
E)1.82

Question 58

Trihydroxybenzoic acid (THB)is a not-so-weak acid with an ionization constant: K_a = 2.1 × 10^-2. Calculate the [H⁺] and the pH of a 0.050 molar solution of THB.Hint: Simplified assumptions do not work in this case.

A)1.9 × 10^-2, 1.72
B)2.4 × 10^-2, 1.63
C)2.5 × 10^-2, 1.59
D)3.2 × 10^-2, 1.49
E)1.1 × 10^-3, 2.98

Question 59

Dichloroacetic acid HC₂HCl₂O₂, is a not-so-weak acid with an ionization constant:K_a = 5.5 × 10^-2. Calculate the [H⁺] and the pH of a 0.100 molar solution of this acid.Hint: Simplified assumptions do not work in this case.

A)1.9 × 10^-2, 1.72
B)5.2 × 10^-2, 1.29
C)2.5 × 10^-2, 1.59
D)3.2 × 10^-2, 1.49
E)1.1 × 10^-3, 2.98

Question 60

The ionization constant, K_a, for HCN(aq)is 6.2 × 10^-10. What is the pH of a 0.10 molar solution of sodium cyanide, which contains the cyanide ion?

A)5.10
B)8.90
C)9.21
D)11.10
E)11.30

Question 61

The ionization constant, K_a, for HOI(aq), hypoiodous acid, is 2.3 × 10^-11. What is the pH of a 0.050 molar solution of sodium hypoiodite, which contains the hypoiodite ion, OI^-?

A)5.97
B)8.03
C)10.64
D)11.65
E)12.70

Question 62

What is the pH of a 1.00 molar solution of KCl?

A)0.00
B)6.90
C)7.00
D)7.10
E)13.00

Question 63

What is the pH of a 1.00 molar solution of NH₄Cl(aq)? The K_b for NH₃ is 1.8 × 10^-5.

A)2.37
B)4.63
C)9.26
D)9.37
E)11.63

Question 64

What is the pH of a 1.00 × 10^-9 molar solution of NaCl?

A)5.00
B)6.00
C)6.80
D)7.00
E)9.00

Question 65

What is the pH of a 1.00 molar solution of NaCN(aq)? The K_a for HCN = 6.2 × 10^-10.

A)2.40
B)4.61
C)9.40
D)11.60
E)13.00

Question 66

What is the pH of a 1.00 molar solution of NaNO₂(aq)? The K_a for HNO₂ is 7.0 × 10^-4.

A)1.57
B)3.15
C)5.42
D)8.58
E)10.85

Question 67

What is the pH of a 1.00 molar solution of NaNO₃(aq)?

A)6.00
B)6.90
C)7.00
D)7.10
E)13.00

Question 68

What is the pH of a 1.00 molar solution of NaC₂H₃O₂(aq)?The K_a for acetic acid (HC₂H₃O₂)is 1.8 × 10^-5.

A)2.37
B)4.63
C)4.75
D)9.37
E)11.63

Question 69

What is the pH of a 1.00 molar solution of NaBr(aq)?

A)0.00
B)6.90
C)7.00
D)7.10
E)13.00

Question 70

A buffer solution is prepared by taking 0.400 moles of acetic acid (pK_a = 4.76)and 0.250 moles of sodium acetate in sufficient water to make 1.400 liters of solution. Calculate the pH of this solution.

A)4.46
B)4.56
C)4.66
D)4.86
E)4.96

Question 71

For H₃PO₃, K_a1 = 1.0 × 10^-2 and K_a2 = 2.6 × 10^-7. Calculate a value for the [H₂PO₃^?] in a 0.500 molar solution of H₃PO₃.

A)1.0 × 10^-2 mol L^-1
B)6.6 × 10^-2 mol L^-1
C)7.1 × 10^-2 mol L^-1
D)8.5 × 10^-3 mol L^-1
E)3.3 × 10^-3 mol L^-1

Question 72

A buffer solution is prepared by taking 0.250 moles of acetic acid (pK_a = 4.76)and 0.400 moles of sodium acetate in sufficient water to make 1.800 liters of solution. Calculate the pH of this solution.

A)4.56
B)4.66
C)4.86
D)4.96
E)5.06

Question 73

A buffer solution is prepared by taking 0.400 moles of acetic acid (pK_a = 4.76)and 0.250 moles of calcium acetate in sufficient water to make 1.400 liters of solution. Calculate the pH of this solution.

A)4.46
B)4.56
C)4.66
D)4.86
E)4.96

Question 74

A buffer solution is prepared by taking 0.250 moles of acetic acid (pK_a = 4.76)and 0.400 moles of barium acetate in sufficient water to make 1.400 liters of solution. Calculate the pH of this solution.

A)4.25
B)4.45
C)5.00
D)5.27
E)5.35

Question 75

The pK_a of acetic acid, HC₂H₃O₂, is 4.76. A buffer solution was made using an unspecified amount of acetic acid and 0.30 moles of NaC₂H₃O₂ in enough water to make 2.00 liters of solution. Its pH was measured as 4.40. How many moles of HC₂H₃O₂ were used?Hint: The opposite operation of log(x)is 10^x.

A)0.13 mol
B)0.18 mol
C)0.60 mol
D)0.69 mol
E)1.37 mol

Question 76

The pK_a of acetic acid, HC₂H₃O₂, is 4.76. A buffer solution was made using an unspecified amount of acetic acid and 0.30 moles of NaC₂H₃O₂ in enough water to make 1.50 liters of solution. Its pH was measured as 4.50 on a meter. How many moles of HC₂H₃O₂ were used?Hint: The opposite operation of log(x)is 10^x.

A)0.31 mol
B)0.55 mol
C)0.61 mol
D)1.09 mol
E)1.21 mol

Question 77

The pK_a of acetic acid, HC₂H₃O₂, is 4.76. A buffer solution was made using an unspecified amount of NaC₂H₃O₂ and 0.30 moles of acetic acid in enough water to make 2.00 liters of solution. Its pH was measured as 4.60. How many moles of NaC₂H₃O₂ were used?Hint: The opposite operation of log(x)is 10^x.

A)0.10 mol
B)0.21 mol
C)0.30 mol
D)0.42 mol
E)0.44 mol

Question 78

The pK_a of acetic acid, HC₂H₃O₂, is 4.76. A buffer solution was made using an unspecified amount of NaC₂H₃O₂ and 0.30 moles of acetic acid in enough water to make 1.50 liters of solution. Its pH was measured as 4.55. How many moles of NaC₂H₃O₂ were used?Hint: The opposite operation of log(x)is 10^x.

A)0.10 mol
B)0.18 mol
C)0.30 mol
D)0.37 mol
E)0.49 mol

Question 79

You have 500.0 mL of a buffer solution containing 0.30 M acetic acid (CH₃COOH)and 0.20 M sodium acetate (CH₃COONa). What will the pH of this solution be after the addition of 20.0 mL of 1.00 M HCl solution? [K_a = 1.8 × 10^-5]Hint: Adding HCl will change the amounts of both the acid and the base. Calculate the pH based on the new amounts.

A)4.74
B)5.07
C)4.71
D)4.56
E)4.42

Question 80

You have 500.0 mL of a buffer solution containing 0.30 M ammonia (NH₃)and 0.20 M ammonium chloride (NH₄Cl). What will the pH of this solution be after the addition of 20.0 mL of 1.00 M HCl solution? [K_b = 1.8 × 10^-5]Hint: Adding HCl will change the amounts of both the acid and the base. Calculate the pH based on the new amounts.

A)4.74
B)9.26
C)9.58
D)9.20
E)9.29