Deck 18: Acid-Base Equilibria

Question 1

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 1

a weak Arrhenius acid.

Question 2

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.

Answer 2

a strong acid.

Question 3

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

Answer 3

H₂SeO₄,H₂SeO₃

Question 4

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 5

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

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

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

Which of the following is the strongest acid?

A)CH₃COOH
B)HF
C)H₃PO₄
D)H₂SO₃
E)HI

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 (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 10

Which one of the following is a strong acid?

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

Question 11

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 12

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 13

Which of the following liquids contains the strongest acid?
0.1 M HA,pH = 6.85
0.1 M HD,pH = 7.22
0.1 M HE,pH = 8.34
0.1 M HJ,pH = 11.88
Pure water

A)HE
B)HA
C)HJ
D)HD
E)pure water

Question 14

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 15

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 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

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 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

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 20

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 21

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 22

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 23

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 24

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 $\times$ 10¹
B)0.16
C)0.099
D)0.0014
E)0.00027

Question 25

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

A)1.4 $\times$ 10^-2 M
B)5.l $\times$ 10^-5 M
C)1.9 $\times$ 10^-10 M
D)7.3 $\times$ 10^-13 M
E)9.71 M

Question 26

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 27

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 28

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 29

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 30

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

A)2.34 $\times$ 10^-4 M
B)2.29 $\times$ 10^-6 M
C)4.37 $\times$ 10^-9 M
D)4.27 $\times$ 10^-11 M
E)8.360 M

Question 31

What is the [OH^-] for a solution at 25°C that has [H₃O⁺] = 2.35 $\times$ 10^-3 M?

A)4.26 $\times$ 10^-5 M
B)2.35 $\times$ 10^-11 M
C)4.26 $\times$ 10^-12 M
D)2.35 $\times$ 10^-17 M
E)None of these choices is correct.

Question 32

The acid dissociation constant K_a equals 1.26 $\times$ 10^-2 for HSO₄^- and is 5.6 $\times$ 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 or 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 33

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 34

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 35

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 $\times$ 10^-2
C)7.8 $\times$ 10^-3
D)1.5 $\times$ 10^-5
E)None of these choices is correct.

Question 36

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 37

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 38

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 39

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 40

What is the [OH^-] for a solution at 25°C that has [H₃O⁺] = 8.23 $\times$ 10^-2 M?

A) > 10^-5 M
B)1.22 $\times$ 10^-6 M
C)8.23 $\times$ 10^-12 M
D)1.22 $\times$ 10^-13 M
E)8.23 $\times$ 10^-16 M

Question 41

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 42

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

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

Question 43

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 44

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 45

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 46

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 $\times$ 10^-4,K₂ = 5.6 $\times$ 10^-8,and K₃ = 3 $\times$ 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 47

A 0.050 M solution of the weak acid HA has [H₃O⁺] = 3.77 $\times$ 10^-4 M.What is the K_a for the acid?

A)7.5 $\times$ 10^-3 M
B)2.8 $\times$ 10^-6 M
C)7.0 $\times$ 10^-7 M
D)7.0 $\times$ 10^-8 M
E)2.6 $\times$ 10^-11 M

Question 48

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 49

Arsenic acid,H₃AsO₄,is used industrially to manufacture insecticides.Arsenic acid is a polyprotic acid with K₁ = 2.5 $\times$ 10^-4,K₂ = 5.6 $\times$ 10^-8,and K₃ = 3 $\times$ 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 $\times$ 10^-3 M
B)2.5 $\times$ 10^-4 M
C)8.8 $\times$ 10^-5 M
D)5.6 $\times$ 10^-8 M
E)None of these choices is correct.

Question 50

What is the value of K_b for the cyanide anion,CN^-?
K_a(HCN)= 6.2 $\times$ 10^-10

A)1.6 $\times$ 10^-4
B)1.6 $\times$ 10^-5
C)3.8 $\times$ 10^-4
D)3.8 $\times$ 10^-5
E)6.2 $\times$ 10⁴

Question 51

Which of the following aqueous liquids is the most acidic?

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

Question 52

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 53

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 54

What is the pH of a 0.0100 M sodium benzoate solution?
K_b (C₇H₅O₂^-)= 1.5 $\times$ 10^-10

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

Question 55

What is the pH of a 0.050 M triethylamine, (C₂H₅)₃N,solution?
K_b for triethylamine is 5.3 $\times$ 10^-4.

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

Question 56

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 57

What is the value of K_a for the methylammonium ion,CH₃NH₃⁺?
K_b(CH₃NH₂)= 4.4 $\times$ 10^-4

A)4.4 $\times$ 10^-4
B)4.8 $\times$ 10^-6
C)4.4 $\times$ 10^-10
D)2.3 $\times$ 10^-11
E)4.4 $\times$ 10^-18

Question 58

Hydroxylamine,HONH₂,readily forms salts such as hydroxylamine hydrochloride which are used as antioxidants in soaps.Hydroxylamine has K_b of 9.1 $\times$ 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 59

What is the value of K_b for the formate anion,HCOO^-?
K_a(HCOOH)= 2.1 $\times$ 10^-4

A)-2.1 $\times$ 10^-4
B)2.1 $\times$ 10^-4
C)6.9 $\times$ 10^-6
D)4.8 $\times$ 10^-11
E)2.1 $\times$ 10^-18

Question 60

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

A)4.2 $\times$ 10^-3 M
B)8.4 $\times$ 10^-3 M
C)1.8 $\times$ 10^-4 M
D)1.8 $\times$ 10^-5 M
E)1.8 $\times$ 10^-6 M

Question 61

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 62

Define a base according to the Brønsted-Lowry theory.Write a balanced equation in support of this definition,in which the base is acting as a Brønsted-Lowry base but not as an Arrhenius base.

Question 63

The pH of a 0.200 M solution of the weak base pyridine,C₅H₅N,is 8.59.Draw up a reaction table for the reaction of 0.200 M pyridine with water,and calculate K_b.

Question 64

Define an acid according to the Arrhenius theory,and write a balanced equation to support this definition.

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 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 67

Consider the reaction:
BF₃ + F^- $\to$ BF₄^-
Can this ever be considered to be an acid-base reaction? Support your answer with appropriate arguments.

Question 68

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 69

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 70

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 71

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 72

Define an acid according to the Lewis theory.Write a balanced equation in support of this definition,in which the acid is neither an Arrhenius acid nor a Brønsted-Lowry acid.

Question 73

The English are fond of soggy French fries ("chips")wrapped in old newspaper and generously drenched in vinegar,which is a 0.83 M solution of acetic acid.If the acetic acid in vinegar is 0.47% dissociated,calculate K_a for this acid.

Question 74

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 75

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

Question 76

Formic acid,HCOOH,is a weak acid with a pK_a of 3.74.Draw up a reaction table for the reaction of 0.300 M formic acid with water,and calculate the pH of this solution.

Question 77

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 78

Which of the following is considered a Lewis acid?

A)CH₃NH₂
B)BCl₃
C)F^-
D)BF₄^-
E)CH₄

Question 79

(a)Write a balanced equation representing the reaction of the acid,H ₂PO₄^- with the base,water.
(b)Write the expression for K_a of H₂PO₄^- in terms of concentrations of relevant species.

Question 80

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.