Deck 18: Acid-Base Equilibria

Question 1

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

A) H₂AsO₃, H₂AsO₄
B) HI, HBr
C) HClO, HClO₃
D) H₂S, HCl
E) H₂SO₃, H₂SO₄

Answer 1

HI, HBr

Question 2

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.

Answer 2

a weak Arrhenius acid.

Question 3

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.

Answer 3

a strong Arrhenius base.

Question 4

Which one of the following is a strong acid?

A) H₂CO₃
B) H₂SO₃
C) H₂SO₄
D) H₃PO₄
E) CH₃COOH

Question 5

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 6

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 7

Which of the following is the strongest acid?

A) CH₃COOH
B) HF
C) H₃PO₄
D) H₂SO₃
E) HI

Question 8

Which of the following is the strongest base?

A) CH₃NH₂
B) NaNO₃
C) B(OH)₃
D) Al(OH)₃
E) LiOH

Question 9

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

A) HBr, HI
B) HClO₂, HClO₃
C) H₂SeO₄, H₂SeO₃
D) HNO₂, HNO₃
E) HF, HCl

Question 10

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 11

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

A) CH₃NH₂
B) NaOH
C) CO₂
D) Ca(OH)₂
E) CH₄

Question 12

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 13

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 14

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 15

Select the strongest acid from the following list.

A) HBrO₄
B) HClO
C) HBrO₂
D) HBrO
E) HIO

Question 16

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 17

Given: H₂O(aq) + H₂O(l) H₃O⁺(aq) + OH^-(aq) ΔH°_rxn > 0 When 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 18

Which of the following is the strongest acid?

A) CH₃COOH
B) HF
C) H₃PO₄
D) H₂SO₃
E) H₂SO₄

Question 19

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 20

Select the strongest acid from the following list.

A) HBrO
B) HBrO₂
C) HClO₂
D) HClO₃
E) HIO

Question 21

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 22

Which of the following acids has the lowest pH? 0.1 M HBO, pK_a = 2.43
0)1 M HA, pK_a = 4.55
0)1 M HMO, pK_a = 8.23
0)1 M HST, pK_a = 11.89
Pure water

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

Question 23

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) [H₂O] > [A^-] ~ [H₃O⁺] > [HA] > [OH^-]
B) [H₂O] > [HA] > [A^-] > [H₃O⁺] > [OH^-]
C) [HA] > [H₂O] > [A^-] > [H₃O⁺] > [OH^-]
D) [H₂O] > [HA] > [A^-] ~ [H₃O⁺] > [OH^-]
E) [HA] > [H₂O] > [A^-] ~ [H₃O⁺] > [OH^-]

Question 24

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 25

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 26

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 27

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(H₂O)₅OH²⁺(aq) + H₃O⁺(aq)
B) Al(H₂O)₆H⁴⁺(aq) + OH^-(aq)
C) Al(H₂O)₅³⁺(aq) + 2H₂O(l)
D) Al(H₂O)₆OH²⁺(aq) + H₃O⁺(aq)
E) Al(H₂O)₆²⁺(aq) + H₃O⁺(aq)

Question 28

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 29

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 30

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 31

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 32

Which of the following aqueous systems has the highest pH?

A) 0.1 M HA, pK_a = 11.89
B) 0.1 M HMO, pK_a = 8.23
C) 0.1 M HA, pK_a = 4.55
D) 0.1 M HBO, pK_a = 2.43
E) pure water

Question 33

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 34

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 35

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 36

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 37

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 38

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 39

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 40

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 41

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 42

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 43

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 44

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

Question 45

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 46

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? HSO_4-(aq) + NH₃(aq) SO₄^2-(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 47

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, HC₂O₄, is a stronger base than the dihydrogen phosphate anion, H₂PO₄.
C) Phosphoric acid is a weaker acid than oxalic acid.
D) The dihydrogen phosphate anion, H₂PO₄^-, is a stronger acid than oxalic acid.
E) Water is a stronger acid than either oxalic or phosphoric acids.

Question 48

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 49

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

A) H₃O⁺/OH^-
B) CH₃OH₂⁺/CH₃OH
C) HI/I^-
D) HSO₄^-/SO₄^2-
E) H₂/H^-

Question 50

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

A) H₃O⁺, H₂O
B) HNO₂, NO₂^-
C) H₂SO₄, HSO₄^-
D) H₂S, S^2-
E) NH₃, NH₂^-

Question 51

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

A) H⁺, HCl
B) NH₃, NH₄+
C) HPO₄^2-, H₂PO^4-
D) HCO₃^-, CO₃^2-
E) CH₃COOH, CH₃COOH₂⁺

Question 52

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 53

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 54

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 55

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 56

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

A) H₂O/OH^-
B) H₂O₂/HO₂^-
C) OH^-/O^2-
D) H₂PO₄^-/HPO₄^2-
E) HCl/H⁺

Question 57

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 58

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 × 10¹
B) 0.16
C) 0.099
D) 0.0014
E) 0.00027

Question 59

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 60

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 HAsO₄^2- 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 61

A solution is prepared by adding 0.10 mol of sodium fluoride, NaF, to 1.00 L of water. Which statement about the solution is correct?

A) The solution is basic.
B) The solution is neutral.
C) The solution is acidic.
D) The concentrations of fluoride ions and sodium ions will be identical.
E) The concentration of fluoride ions will be greater than the concentration of sodium ions.

Question 62

What is the value of K_b for the cyanide anion, CN-? _Ka(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 × 10⁴

Question 63

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 64

Which one of the following substances will give an aqueous solution of pH closest to 7?

A) KNO₃
B) CO₂
C) NH₄I
D) NH₃
E) CH₃NH₂

Question 65

A solution is prepared by adding 0.10 mol of sodium sulfide, Na₂S, to 1.00 L of water. Which statement about the solution is correct?

A) The solution is basic.
B) The solution is neutral.
C) The solution is acidic.
D) The concentration of sodium ions and sulfide ions will be identical.
E) The concentration of sulfide ions will be greater than the concentration of sodium ions.

Question 66

Calcium oxide, CaO, also known as quick lime, will react with carbon dioxide to form calcium carbonate, CaCO₃. Which species, if any, acts as a Lewis acid in the reaction?

A) Ca²⁺
B) O^2-
C) CO₂
D) CaCO₃
E) None of these choices are correct.

Question 67

Ammonium chloride is used as an electrolyte in dry cells. Which of the following statements about a 0.10 M solution of NH₄Cl, is correct?

A) The solution is weakly basic.
B) The solution is strongly basic.
C) The solution is neutral.
D) The solution is acidic.
E)The values for K_a and K_b for the species in solution must be known before a prediction can be made.

Question 68

Which of the following is a Lewis base?

A) BCl₃
B) Cu²⁺
C) Cl^-
D) Mn²⁺
E) NH₄⁺

Question 69

A solution is prepared by adding 0.10 mol of iron(III) nitrate, Fe(NO₃)₃, to 1.00 L of water. Which statement about the solution is correct?

A) The solution is basic.
B) The solution is neutral.
C) The solution is acidic.
D) The value of K_a for the species in solution must be known before a prediction can be made.
E) The value of K_b for the species in solution must be known before a prediction can be made.

Question 70

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 71

Which of the following aqueous liquids is the most acidic?

A) 0.1 M Al(NO₃)₃, K_a = 1 × 10^-5
B) 0.1 M Be(NO₃)₂, K_a = 4 × 10^-6
C) 0.1 M Pb(NO₃)₂, K_a = 3 × 10^-8
D) 0.1 M Ni(NO₃)₂, K_a = 1 × 10^-10
E) pure water

Question 72

Which one of the following substances will give an aqueous solution of pH < 7?

A) KI
B) NH₄Br
C) Na₂CO₃
D) CH₃COONa
E) CH₃OH

Question 73

Which of the following aqueous liquids will have the highest pH?

A) 0.1 M CH₃COOH, pK_a = 4.7
B) 0.1 M CuCl₂, pK_a = 7.5
C) 0.1 M H₃C₆H₅O₇, pK_a = 3.1
D) 0.1 M ZnCl₂, pK_a = 9.0
E) pure water

Question 74

A solution is prepared by adding 0.10 mol of potassium chloride, KCl, to 1.00 L of water. Which statement about the solution is correct?

A) The solution is basic.
B) The solution is neutral.
C) The solution is acidic.
D) One needs to know the temperature before any of these predictions can be made.
E) The values for K_a and K_b for the species in solution must be known before a prediction can be made.

Question 75

An aqueous solution is prepared by dissolving the salt formed by the neutralization of a weak acid by a weak base. Which statement about the solution is correct?

A) The solution is strongly basic.
B) The solution is weakly basic.
C) The solution is neutral.
D) The solution is acidic.
E) The values for K_a and K_b for the species in solution must be known before a prediction can be made.

Question 76

Iodine trichloride, ICl₃, will react with a chloride ion to form ICl₄^-. Which species, if any, acts as a Lewis acid this reaction?

A) ICl₄^-
B) ICl₃
C) Cl^-
D) the solvent
E) None of these choices are correct.

Question 77

Which of the following is considered a Lewis acid?

A) CH₃NH₂
B) BCl₃
C) F^-
D) BF₄^-
E) CH₄

Question 78

A solution is prepared by adding 0.10 mol of potassium acetate, KCH₃COO, to 1.00 L of water. Which statement about the solution is correct?

A) The solution is basic.
B) The solution is neutral.
C) The solution is acidic.
D) The concentrations of potassium ions and acetate ions will be identical.
E) The concentration of acetate ions will be greater than the concentration of potassium ions.

Question 79

What is the pH of a 0.010 M triethanolammonium chloride, (HOC₂H₂)₃NHCl, solution? K_b, ((HOC₂H₂)₃N) = 5.9 × 10^-7

A) 2.75
B) 4.89
C) 9.11
D) 11.25
E) None of these choices are correct.

Question 80

A solution is prepared by adding 0.10 mol of lithium nitrate, LiNO₃, to 1.00 L of water. Which statement about the solution is correct?

A) The solution is basic.
B) The solution is neutral.
C) The solution is weakly acidic.
D) The solution is strongly acidic.
E) The values for K_a and K_b for the species in solution must be known before a prediction can be made.