Deck 18: Acid-Base Equilibria

Question 1

Select the strongest acid from the following list.

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

Answer 1

HBrO₄

Question 2

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.

Answer 2

a strong Arrhenius base.

Question 3

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.

Answer 3

a weak base.

Question 4

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 5

Which of the following is the strongest acid?

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

Question 6

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 7

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

A) phosphoric
B) carbonic
C) acetic
D) water
E) none of the above

Question 8

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 9

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 10

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 11

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 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

Select the strongest acid from the following list.

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

Question 14

Given: H₂O(aq) + H₂O(l) H₃O⁺(aq) + OH^-(aq) $\Delta$ H°_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 15

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 16

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 17

Which one of the following is a strong acid?

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

Question 18

Which of the following is the strongest base?

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

Question 19

Which of the following is the strongest acid?

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

Question 20

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

Question 21

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 the above

Question 22

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 23

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 24

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 the above

Question 25

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 the above

Question 26

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 the above

Question 27

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 the above

Question 28

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) $\to$ ?

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 29

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 30

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 31

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 32

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 the above

Question 33

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 the above

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 the above

Question 35

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 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

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 38

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 39

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

A) H⁺, HCl
B) NH₃, NH₄⁺
C) HPO₄^2-, H₂PO₄^-
D) HCO₃^-, CO₃^2-
E) CH₃COOH, CH₃COOH₂⁺

Question 40

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 41

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 the above

Question 42

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 43

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 the above

Question 44

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 45

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 the above

Question 46

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 47

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 48

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 49

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 the above

Question 50

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, HPO₄^2-?

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 51

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 52

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 53

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 × 10⁴

Question 54

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 55

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 the above

Question 56

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 57

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) 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 58

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 the above

Question 59

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 60

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

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

Question 61

Which of the following is considered a Lewis acid?

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

Question 62

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 63

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.

Question 64

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 65

Which of the following is a Lewis base?

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

Question 66

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 67

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 the species acts as a Lewis acid in this reaction.

Question 68

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 69

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 70

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 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 is a Lewis acid but not a Brønsted-Lowry acid?

A) Fe³⁺
B) H₃O⁺
C) HSO₄^-
D) NH₃
E) H₂O

Question 73

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) ICl ₃
C) Cl^-
D) the solvent
E) None of the species acts as a Lewis acid in this reaction.

Question 74

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 the above

Question 75

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 76

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 the above 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 77

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 78

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 79

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 80

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