Deck 18: Acid-Base Equilibria

Question 1

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

A) phosphoric
B) carbonic
C) acetic
D) water
E) None of these choices is correct.

Answer 1

None of these choices is correct.

Question 2

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.

Answer 2

a neutral compound.

Question 3

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

Answer 3

CH₃NH₂

Question 4

Given: When the temperature of a sample of pure water is raised above 25 $\degree$ 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 5

Which of the following is the strongest base?

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

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

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 8

Select the strongest acid from the following list.

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

Question 9

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 10

Which of the following is the strongest acid?

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

Question 11

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 12

Which of the following is the strongest acid?

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

Question 13

Select the strongest acid from the following list.

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

Question 14

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 15

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 16

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 17

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 18

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 19

Which one of the following is a strong acid?

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

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 [OH¯] for a solution at 25 $\degree$ 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 22

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 23

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 is correct.

Question 24

Which of the following acids has the lowest pH?

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

Question 25

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 26

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 27

What is the [OH¯] for a solution at 25 $\degree$ 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 28

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 29

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 30

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 31

What is the [H₃O⁺] for a solution at 25 $\degree$ 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 32

What is the [OH¯] for a solution at 25 $\degree$ 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 is correct.

Question 33

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 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 is correct.

Question 35

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 is correct.

Question 36

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 is correct.

Question 37

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 is correct.

Question 38

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) $\rightarrow$ ?

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 39

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 is correct.

Question 40

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 is correct.

Question 41

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 is correct.

Question 42

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

A) H₂O, OH¯
B) H₂O₂, HO₂¯
C) OH¯, O²¯
D) H₂PO₄¯, HPO₄²¯
E) HCl, H⁺

Question 43

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 44

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¯, SO₄²¯
E) H₂, H¯

Question 45

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 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

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 48

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

A) H⁺, HCl
B) NH₃, NH₄⁺
C) HPO₄²¯, H₂PO₄¯
D) HCO₃¯, CO₃²¯
E) CH₃COOH, CH₃COOH₂⁺

Question 49

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, HPO₄²¯?

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 50

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 is correct.

Question 51

Aqueous solutions of phosphoric acid and sodium nitrite are combined, and the following equilibrium is established. 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 52

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 is correct.

Question 53

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 is correct.

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

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?

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 56

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 is correct.

Question 57

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

A) H₃O⁺, H₂O
B) HNO₂, NO₂¯
C) H₂SO₄, HSO₄¯
D) H₂S, S²¯
E) NH₃, NH₂¯

Question 58

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?

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 59

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 60

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 is correct.

Question 61

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 62

Which of the following is considered a Lewis acid?

A) CH₃NH₂
B) BCl₃
C) F¯
D) BF₄¯
E) CH₄

Question 63

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 64

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 65

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 66

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 67

Which of the following is a Lewis base?

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

Question 68

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 69

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 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 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 72

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 73

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 74

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 75

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

A) ICl₄¯
B) ICl₃
C) Cl¯
D) the solvent
E) None of the species acts as a Lewis acid in this reaction.

Question 76

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) O²¯
C) CO₂
D) CaCO₃
E) None of the species acts as a Lewis acid in this reaction.

Question 77

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 is correct.

Question 78

(p. 812 and other sections) 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 79

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 80

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

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