Deck 18: Acid-Base Equilibria

Question 1

The chloride ion, Cl⁻, is a typical Lewis acid.

Answer 1

False

Question 2

The ammonium ion, NH₄⁺, is a weak acid.

Answer 2

True

Question 3

Hydrated metal ions in aqueous solution can act as Brønsted-Lowry acids.

Answer 3

True

Question 4

In applying molecular orbital theory, the bond order is calculated in the same way as with Lewis structures.

Question 5

It is not possible to have a pH lying outside the range 0 to 14.

Question 6

The substance HCl is considered

A)a weak Arrhenius acid.
B)a weak Arrhenius base.
C)a strong Arrhenius acid.
D)a strong Arrhenius base.
E)a neutral compound.

Question 7

All Brønsted-Lowry bases have at least one lone pair of electrons.

Question 8

In order to be a Brønsted-Lowry base, a species must contain a proton.

Question 9

A solution of sodium acetate (CH₃COONa) in water is weakly basic.

Question 10

All strong acids have weak conjugate bases.

Question 11

The substance H₂SO₃ is considered

A)a weak Arrhenius base.
B)a strong Arrhenius acid.
C)a strong Arrhenius base.
D)a neutral compound.
E)a weak Arrhenius acid.

Question 12

If a strong acid such as HCl is diluted sufficiently with water, the pH will be higher than 7.

Question 13

All weak acids have strong conjugate bases.

Question 14

If the compound HX is a strong acid (where H is the acidic proton in this acid), then the ion X⁻ is a weak base.

Question 15

All Brønsted-Lowry bases contain the hydroxide ion, OH⁻.

Question 16

The strongest base which can exist in water is the hydroxide ion.

Question 17

Arrhenius bases raise the hydroxide ion concentration when dissolved in water.

Question 18

Kw = 1.0 × 10⁻¹⁴, regardless of temperature.

Question 19

All Lewis acids contain at least one proton.

Question 20

The substance HOBr is considered

A)a weak Arrhenius acid.
B)a weak Arrhenius base.
C)a strong Arrhenius acid.
D)a strong Arrhenius base.
E)a neutral compound.

Question 21

Which of the following liquids contains the strongest acid?

A)0.1 M HA, pH = 6.85
B)0.1 M HD , pH = 7.22
C)0.1 M HE, pH = 8.34
D)0.1 M HJ , pH = 11.88
E)Pure water

Question 22

Given: H₂O(aq) + H₂O(l) ⇄ H₃O⁺(aq) + OH^-(aq) ΔH°_rxn > 0When the temperature of a sample of pure water is raised above 25°C,

A)the hydronium ion concentration will be greater than the hydroxide ion concentration.
B)the hydronium ion concentration will be less than the hydroxide ion concentration.
C)the value of K _w will increase.
D)the hydronium ion concentration could change to 1.0 × 10 ⁻¹⁰ M.
E)the hydroxide ion concentration could change to 1.0 × 10 ⁻¹⁰ M.

Question 23

The substance (CH₃CH₂)₂NH is considered

A)a weak acid.
B)a weak base.
C)a strong acid.
D)a strong base.
E)a neutral compound.

Question 24

Which of the following is the strongest base?

A)CH ₃NH ₂
B)NaNO ₃
C)B(OH)₃
D)Al(OH)₃
E)LiOH

Question 25

Which, if any, of the following acids is strong?

A)Phosphoric
B)Carbonic
C)Acetic
D)Water
E)None of these choices are correct.

Question 26

The substance NaNO₃ is considered

A)a weak Arrhenius acid.
B)a weak Arrhenius base.
C)a strong Arrhenius acid.
D)a strong Arrhenius base.
E)a neutral compound.

Question 27

The substance Ba(OH)₂ is considered

A)a weak Arrhenius acid.
B)a weak Arrhenius base.
C)a strong Arrhenius acid.
D)a strong Arrhenius base.
E)a neutral compound.

Question 28

Select the strongest acid from the following list.

A)HBrO ₄
B)HClO
C)HBrO ₂
D)HBrO
E)HIO

Question 29

Which of the following aqueous systems has the highest pH?

A)0.1 M HA , p K _a = 11.89
B)0.1 M HMO, p K _a = 8.23
C)0.1 M HA , p K _a = 4.55
D)0.1 M HBO, p K _a = 2.43
E)Pure water

Question 30

Which of the following is the strongest acid?

A)CH ₃COOH
B)HF
C)H ₃PO ₄
D)H ₂SO ₃
E)HI

Question 31

Select the strongest acid from the following list.

A)HBrO
B)HBrO ₂
C)HClO ₂
D)HClO ₃
E)HIO

Question 32

Which one of the following is a strong acid?

A)H ₂CO ₃
B)H ₂SO ₃
C)H ₂SO ₄
D)H ₃PO ₄
E)CH ₃COOH

Question 33

Which of the following is the strongest acid?

A)CH ₃COOH
B)HF
C)H ₃PO ₄
D)H ₂SO ₃
E)H ₂SO ₄

Question 34

Which of the following pairs has the stronger acid listed first?

A)HBr, HI
B)HClO ₂, HClO ₃
C)H ₂SeO ₄, H ₂SeO ₃
D)HNO ₂, HNO ₃
E)HF, HCl

Question 35

The substance HClO₄ is considered

A)a weak acid.
B)a weak base.
C)a strong acid.
D)a strong base.
E)a neutral compound.

Question 36

The substance Ca(OH)₂ is considered

A)a weak Arrhenius acid.
B)a weak Arrhenius base.
C)a strong Arrhenius acid.
D)a strong Arrhenius base.
E)a neutral compound.

Question 37

Which one of the following will give a solution with a pH > 7, but is not an Arrhenius base in the strict sense?

A)CH ₃NH ₂
B)NaOH
C)CO ₂
D)Ca(OH)₂
E)CH ₄

Question 38

The substance NH₃ is considered

A)a weak acid.
B)a weak base.
C)a strong acid.
D)a strong base.
E)a neutral compound.

Question 39

Which of the following pairs has the stronger acid listed first?

A)H ₂AsO ₃, H ₂AsO ₄
B)HI, HBr
C)HClO, HClO ₃
D)H ₂S, HCl
E)H ₂SO ₃, H ₂SO ₄

Question 40

Which of the following acids has the lowest pH?0.1 M HBO, pK_a = 2.430.1 M HA, pK_a = 4.550.1 M HMO, pK_a = 8.230.1 M HST, pK_a = 11.89pure water

A)HA
B)HST
C)HMO
D)HBO
E)Pure water

Question 41

What is the pH of a 0.75 M HNO₃ solution?

A)0.12
B)0.29
C)0.63
D)0.82
E)> 1.0

Question 42

What is the pOH of a 0.0085 M KOH solution?

A)2.07
B)4.77
C)9.23
D)11.93
E)None of these choices are correct.

Question 43

What is the [OH⁻] for a solution at 25°C that has [H₃O⁺] = 2.35 × 10⁻³ M?

A)4.26 × 10 ⁻⁵ M
B)2.35 × 10 ⁻¹¹ M
C)4.26 × 10 ⁻¹² M
D)2.35 × 10 ⁻¹⁷ M
E)None of these choices are correct.

Question 44

Select the pair of substances in that an acid is listed followed by its conjugate base.

A)H ⁺, HCl
B)NH ₃, NH ₄ ⁺
C)HPO ₄ ²⁻, H ₂PO ₄ ⁻
D)HCO ₃ ⁻, CO ₃ ²⁻
E)CH ₃COOH, CH ₃COOH ₂ ⁺

Question 45

What is the pH of a 0.0035 M KOH solution?

A)2.46
B)5.65
C)8.35
D)11.54
E)None of these choices are correct.

Question 46

What is the pH of a 0.050 M HBr solution?

A)0.89
B)1.12
C)1.30
D)3.00
E)None of these choices are correct.

Question 47

What is the pH of a 0.20 M HCl solution?

A)< 0
B)0.70
C)1.61
D)12.39
E)13.30

Question 48

Select the correct relationship among the concentrations of species present in a 1.0 M aqueous solution of the weak acid represented by HA.

A)[H ₂O] > [A ⁻] ~ [H ₃O ⁺] > [HA] > [OH ⁻]
B)[H ₂O] > [HA] > [A ⁻] > [H ₃O ⁺] > [OH ⁻]
C)[HA] > [H ₂O] > [A ⁻] > [H ₃O ⁺] > [OH ⁻]
D)[H ₂O] > [HA] > [A ⁻] ~ [H ₃O ⁺] > [OH ⁻]
E)[HA] > [H ₂O] > [A ⁻] ~ [H ₃O ⁺] > [OH ⁻]

Question 49

What is the [OH⁻] for a solution at 25°C that has [H₃O⁺] = 8.23 × 10⁻² M?

A)> 10 ⁻⁵ M
B)1.22 × 10 ⁻⁶ M
C)8.23 × 10 ⁻¹² M
D)1.22 × 10 ⁻¹³ M
E)8.23 × 10 ⁻¹⁶ M

Question 50

The hydrated Al³⁺ ion, Al(H₂O)₆³⁺, is a weak acid in water. What are the products of its reaction with H₂O?Al(H₂O)₆³⁺(aq) + H₂O(l) → ?

A)Al(H ₂O)₅OH ²⁺( aq)+ H ₃O ⁺( aq)
B)Al(H ₂O)₆H ⁴⁺( aq)+ OH ⁻( aq)
C)Al(H ₂O)₅ ³⁺( aq)+ 2H ₂O( l)
D)Al(H ₂O)₆OH ²⁺( aq)+ H ₃O ⁺( aq)
E)Al(H ₂O)₆ ²⁺( aq)+ H ₃O ⁺( aq)

Question 51

What is the pH of a 0.050 M LiOH solution?

A)< 1.0
B)1.30
C)3.00
D)11.00
E)12.70

Question 52

What is the [OH⁻] for a solution at 25°C that has pH = 4.29?

A)1.4 × 10 ⁻² M
B)5.l × 10 ⁻⁵ M
C)1.9 × 10 ⁻¹⁰ M
D)7.3 × 10 ⁻¹³ M
E)9.71 M

Question 53

What is the [H₃O⁺] for a solution at 25°C that has pOH = 5.640?

A)2.34 × 10 ⁻⁴ M
B)2.29 × 10 ⁻⁶ M
C)4.37 × 10 ⁻⁹ M
D)4.27 × 10 ⁻¹¹ M
E)8.360 M

Question 54

An aqueous solution is considered to be acidic if

A)the hydroxide ion concentration is 10 ⁻⁶ M.
B)the hydrogen ion concentration is 10 ⁻⁸ M.
C)the hydroxide and hydrogen ion concentrations are equal.
D)the hydroxide ion concentration is greater than the hydrogen ion concentration.
E)the hydroxide ion concentration is 10 ⁻¹⁰ M.

Question 55

Select the pair of substances that is not a conjugate acid-base pair.

A)H ₃O ⁺, H ₂O
B)HNO ₂, NO ₂ ⁻
C)H ₂SO ₄, HSO ₄ ⁻
D)H ₂S, S ²⁻
E)NH ₃, NH ₂ ⁻

Question 56

What is the pOH of a 0.0250 M HI solution?

A)0.944
B)1.602
C)12.398
D)13.056
E)None of these choices are correct.

Question 57

When 14.7 mL of aqueous HBr (a strong acid) was added to water, 0.482 L of a solution with a pH of 4.23 was produced. What was the molarity of the original HBr solution?

A)1.9 × 10 ⁻³ M
B)140 M
C)0.288 M
D)0.13 M
E)None of these choices are correct.

Question 58

What is the pH of a 0.0125 M NaOH solution?

A)0.972
B)1.903
C)12.097
D)13.028
E)None of these choices are correct.

Question 59

What is the pH of a 0.00200 M HClO₄ solution?

A)0.995
B)1.378
C)2.699
D)6.215
E)None of these choices are correct.

Question 60

Which one of the following pairs is not a conjugate acid-base pair?

A)H ₂O/OH ⁻
B)H ₂O ₂/HO ₂ ⁻
C)OH ⁻/O ²⁻
D)H ₂PO ₄ ⁻/HPO ₄ ²⁻
E)HCl/H ⁺

Question 61

The acid dissociation constant K_a equals 1.26 × 10⁻² for HSO₄⁻ and is 5.6 × 10⁻¹⁰ for NH₄. Which statement about the following equilibrium is correct?HSO₄⁻(aq) + NH₃(aq)⇄ SO₄²⁻(aq) + NH₄⁺(aq)

A)The reactants will be favored because ammonia is a stronger base than the sulfate anion.
B)The products will be favored because the hydrogen sulfate ion is a stronger acid than the ammonium ion.
C)Neither reactants nor products will be favored because all of the species are weak acids or bases.
D)The initial concentrations of the hydrogen sulfate ion and ammonia must be known before any prediction can be made.
E)This reaction is impossible to predict, since the strong acid and the weak base appear on the same side of the equation.

Question 62

What is the value of K_b for the cyanide anion, CN⁻? K_a(HCN) = 6.2 × 10⁻¹⁰

A)1.6 × 10 ⁻⁴
B)1.6 × 10 ⁻⁵
C)3.8 × 10 ⁻⁴
D)3.8 × 10 ⁻⁵
E)6.2 × 10 ⁴

Question 63

According to Brønsted and Lowry, which one of the following is not a conjugate acid-base pair?

A)H ₃O ⁺/OH ⁻
B)CH ₃OH ₂ ⁺/CH ₃OH
C)HI/I ⁻
D)HSO ₄ ⁻/SO ₄ ²⁻
E)H ₂/H ⁻

Question 64

What is the pH of a 0.0100 M sodium benzoate solution? K_b (C₇H₅O₂) = 1.5 × 10⁻¹⁰

A)0.38
B)5.91
C)8.09
D)9.82
E)13.62

Question 65

A 0.15 M solution of chloroacetic acid has a pH of 1.86. What is the value of K_a for this acid?

A)7.2 × 10 ¹
B)0.16
C)0.099
D)0.0014
E)0.00027

Question 66

Butyric acid is responsible for the odor in rancid butter. A solution of 0.25 M butyric acid has a pH of 2.71. What is the K_a for the acid?

A)0.36
B)2.4 × 10 ⁻²
C)7.8 × 10 ⁻³
D)1.5 × 10 ⁻⁵
E)None of these choices are correct.

Question 67

A 0.050 M solution of the weak acid HA has [H₃O⁺] = 3.77 × 10⁻⁴ M. What is the K_a for the acid?

A)7.5 × 10 ⁻³ M
B)2.8 × 10 ⁻⁶ M
C)7.0 × 10 ⁻⁷ M
D)7.0 × 10 ⁻⁸ M
E)2.6 × 10 ⁻¹¹ M

Question 68

Lactic acid has a pK_a of 3.08. What is the approximate degree of dissociation of a 0.35 M solution of lactic acid?

A)1.1%
B)2.2%
C)4.8%
D)14%
E)None of these choices are correct.

Question 69

Phosphoric acid, H₃PO₄, is a triprotic acid, for which K_a1 = 7.2 × 10⁻³, K_a2 = 6.3 × 10⁻⁸ and K_a3 = 4.2 × 10⁻¹³. What is the value of K_b for the hydrogen phosphate anion, HPO₄?

A)6.3 × 10 ⁻⁸
B)4.2 × 10 ⁻¹³
C)1.4 × 10 ⁻¹²
D)1.6 × 10 ⁻⁷
E)2.4 × 10 ⁻²

Question 70

What is the value of K_b for the formate anion, HCOO⁻? K_a(HCOOH) = 2.1 × 10⁻⁴

A)−2.1 × 10 ⁻⁴
B)2.1 × 10 ⁻⁴
C)6.9 × 10 ⁻⁶
D)4.8 × 10 ⁻¹¹
E)2.1 × 10 ⁻¹⁸

Question 71

Arsenic acid, H₃AsO₄, is used industrially to manufacture insecticides. Arsenic acid is a polyprotic acid with K₁ = 2.5 × 10⁻⁴, K₂ = 5.6 × 10⁻⁸, and K₃ = 3 × 10⁻¹³. What is the concentration of the HAsO₄²⁻ in a solution whose initial arsenic acid concentration was 0.35 M?

A)9.4 × 10 ⁻³ M
B)2.5 × 10 ⁻⁴ M
C)8.8 × 10 ⁻⁵ M
D)5.6 × 10 ⁻⁸ M
E)None of these choices are correct.

Question 72

Formic acid, which is a component of insect venom, has a K_a = 1.8 × 10⁻⁴. What is the [H₃O⁺] in a solution that is initially 0.10 M formic acid, HCOOH?

A)4.2 × 10 ⁻³ M
B)8.4 × 10 ⁻³ M
C)1.8 × 10 ⁻⁴ M
D)1.8 × 10 ⁻⁵ M
E)1.8 × 10 ⁻⁶ M

Question 73

Picric acid has been used in the leather industry and in etching copper. However, its laboratory use has been restricted because it dehydrates on standing and can become shock sensitive. It has an acid dissociation constant of 0.42. What is the [H₃O⁺] for a 0.20 M solution of picric acid?

A)0.022 M
B)0.052 M
C)0.15 M
D)0.29 M
E)None of these choices are correct.

Question 74

What is the pH of a 0.050 M triethylamine, (C₂H₅)₃N, solution?K_b for triethylamine is 5.3 × 10⁻⁴.

A)11.69
B)8.68
C)5.32
D)2.31
E)< 2.0

Question 75

A student adds 0.1 mol of oxalic acid and 0.1 mol of sodium dihydrogen phosphate to enough water to make 1.0 L of solution. The following equilibrium is established with the concentrations of the products greater than the concentrations of the reactants. Which of the statements about the equilibrium system is correct? H₂C₂O₄(aq) + H₂PO₄(aq)⇄ HC₂O₄(aq) + H₃PO₄(aq)

A)Oxalic acid is a weaker acid than phosphoric acid.
B)The hydrogen oxalate anion, HC ₂O ₄, is a stronger base than the dihydrogen phosphate anion, H ₂PO ₄.
C)Phosphoric acid is a weaker acid than oxalic acid.
D)The dihydrogen phosphate anion, H ₂PO ₄ ⁻, is a stronger acid than oxalic acid.
E)Water is a stronger acid than either oxalic or phosphoric acids.

Question 76

What is the value of K_a for the methylammonium ion, CH₃NH₃⁺? K_b(CH₃NH₂) = 4.4 × 10⁻⁴

A)4.4 × 10 ⁻⁴
B)4.8 × 10 ⁻⁶
C)4.4 × 10 ⁻¹⁰
D)2.3 × 10 ⁻¹¹
E)4.4 × 10 ⁻¹⁸

Question 77

Farmers who raise cotton once used arsenic acid, H₃AsO₄, as a defoliant at harvest time. Arsenic acid is a polyprotic acid with K₁ = 2.5 × 10⁻⁴, K₂ = 5.6 × 10⁻⁸, and K₃ = 3 × 10⁻¹³. What is the pH of a 0.500 M solution of arsenic acid?

A)0.85
B)1.96
C)3.90
D)4.51
E)None of these choices are correct.

Question 78

Aqueous solutions of phosphoric acid and sodium nitrite are combined, and the following equilibrium is established. H₃PO₄(aq) + NO₂(aq)⇄ H₂PO₄(aq) + HNO₂(aq)
The equilibrium constant K_c for this reaction is greater than one. Based on this information, which of the following statements is correct?

A)Phosphoric acid is a weaker acid than nitrous acid.
B)Nitrous acid is a weaker acid than water.
C)The nitrite anion is a weaker base than the dihydrogen phosphate anion.
D)The dihydrogen phosphate anion is a stronger acid than nitrous acid.
E)Phosphoric acid is a stronger acid than nitrous acid.

Question 79

A 1.25 M solution of the weak acid HA is 9.2% dissociated. What is the pH of the solution?

A)0.64
B)0.94
C)1.13
D)2.16
E)None of these choices are correct.

Question 80

Hydroxylamine, HONH₂, readily forms salts such as hydroxylamine hydrochloride which are used as antioxidants in soaps. Hydroxylamine has K_b of 9.1 × 10⁻⁹. What is the pH of a 0.025 M HONH₂ solution?

A)2.90
B)4.82
C)9.18
D)9.91
E)11.10