Deck 15: Acid-Base Equilibria Proton Transfer in Biological Systems

Question 1

Which of the following is a strong acid?

A)nitrous acid, HNO₂
B)sulfurous acid, H₂SO₃
C)carbonic acid, H₂CO₃
D)hydrofluoric acid, HF
E)perchloric acid, HClO₄

Answer 1

perchloric acid, HClO₄

Question 2

Which of the following is NOT a strong base?

A)lithium hydroxide, LiOH
B)sodium hydroxide, NaOH
C)potassium hydroxide, KOH
D)strontium hydroxide, SrOH)₂
E)ammonium hydroxide, NH₄OH

Answer 2

ammonium hydroxide, NH₄OH

Question 3

Three acids found in foods are lactic acid (in milk products), oxalic acid (in rhubarb), and malic acid (in apples).The pK_a values are LA = 3.88, OA =1.23, and MA = 3.40.Which list has these acids in order of decreasing acid strength?

A)LA $\gt$ OA $\gt$ MA
B)LA $\gt$ MA $\gt$ OA
C)OA $\gt$ MA $\gt$ LA
D)OA $\gt$ LA $\gt$ MA
E)MA $\gt$ LA $\gt$ OA

Answer 3

OA $\gt$ MA $\gt$ LA

Question 4

Which of the following is a strong base?

A)CH₃NH₂
B)BaOH)₂
C)H₂O₂
D)CrOH)₃
E)CH₃COOH

Question 5

In the Brønsted-Lowry definition of acids and bases, an acid

A)is a proton donor.
B)is a proton acceptor.
C)forms stable hydrogen bonds.
D)breaks stable hydrogen bonds.
E)corrodes metals.

Question 6

In the Brønsted-Lowry definition of acids and bases, a base

A)is a proton donor.
B)is a proton acceptor.
C)forms stable hydrogen bonds.
D)breaks stable hydrogen bonds.
E)corrodes metals.

Question 7

Three acids found in foods are lactic acid (in milk products), oxalic acid (in rhubarb), and malic acid (in apples).The pK_a values are LA = 3.88, OA = 1.23, and MA = 3.40.Which list has the conjugate bases of these acids in order of decreasing strength?

A)lactate $\gt$ oxalate $\gt$ malate
B)oxalate $\gt$ malate $\gt$ lactate
C)lactate $\gt$ malate $\gt$ oxalate
D)oxalate $\gt$ lactate $\gt$ malate
E)malate $\gt$ lactate $\gt$ oxalate

Question 8

Which of the following statements regarding acid and base ionization in water is NOT correct?

A)A hydrogen atom directly bonded to an oxygen atom in a molecule is always significantly more acidic than water.
B)In strong acids, the acidic protons are generally bonded to highly electronegative elements such as O, Cl, Br, or I.
C)When a hydrogen atom is released as an H⁺ ion from an electronegative atom in an acid, the bonding pair of electrons remains on the electronegative atom.
D)Ionization of a strong acid in water is assisted by the strong dipole-dipole interactions between its ionizable H atoms and the O atoms in water molecules.
E)Ionization of water to form hydroxide in the presence of a base is often assisted by strong dipole-dipole interactions between H atoms in water and a lone pair of electrons in the base.

Question 9

Which of the following is a strong acid?

A)HNO₃
B)H₂S
C)HNO₂
D)HCO₃^-
E)HOCl

Question 10

Given the following K_a values, which of the following acids has the strongest conjugate base in water? benzoic, C₆H₅COOH K_a  6.5  105 chlorous, HClO₂ K_a  1.1  102
Iodic, HIO₃ K_a  1.7  101 acrylic, CH₂  CHCOOH K_a  5.5  105 cyanic, HCNO Ka  3.5  104

A)benzoic
B)chlorous
C)iodic
D)acrylic
E)cyanic

Question 11

Which of these is a strong acid that ionizes to make a weak acid?

A)H₂SO₃
B)H₂SO₄
C)H₃PO₄
D)HNO₃
E)HCl

Question 12

Which of the following is a strong acid?

A)HClO
B)HClO₂
C)HClO₃
D)HClO₄
E)None of these is a strong acid.

Question 13

Given the following K_a values, which of the following acids is the strongest in water? benzoic, C₆H₅COOH K_a  6.5  105 chlorous, HClO₂ K_a  1.1  102
Iodic, HIO₃ K_a  1.7  101 acrylic, CH₂  CHCOOH K_a  5.5  105 cyanic, HCNO Ka  3.5  104

A)benzoic
B)chlorous
C)iodic
D)acrylic
E)cyanic

Question 14

Use the following acid ionization constants to identify the correct decreasing order of base strengths.

A)CN^- $\gt$ NO₂^- $\gt$ F^-
B)NO₂^- $\gt$ F^- $\gt$ CN^-
C)F^- $\gt$ CN^- $\gt$ NO₂^-
D)F^- $\gt$ NO₂^- $\gt$ CN^-
E)NO₂^- $\gt$ CN^- $\gt$ F^-

Question 15

The degree of ionization of a strong acid is

A)100%.
B)between 1% and 10%.
C)between 10% and 100%.
D)dependent on the concentration of the acid.
E)dependent the value of K_a.

Question 16

Which of the following is NOT a strong acid?

A)nitric acid, HNO₃
B)sulfuric acid, H₂SO₄
C)carbonic acid, H₂CO₃
D)hydrochloric acid, HCl
E)perchloric acid, HClO₄

Question 17

The degree of ionization of a weak acid
I.varies with the concentration of the acid.
II.depends on the value of K_a.
III.is 100%.
IV.is greater than 50% but less than 100%.

A)I only
B)II only
C)III only
D)both I and II
E)IV only

Question 18

Which statement about nitrous acid and nitric acid is correct?

A)They are both weak acids.
B)They are both strong acids.
C)They both have one ionizable proton.
D)Nitrous acid has the formula HNO₃.
E)Nitric acid has the formula HNO₂.

Question 19

Which of the following is a strong acid?

A)H₂SO₃
B)H₃PO₄
C)HBrO
D)HF
E)HNO₃

Question 20

Which of the following statements is NOT correct?

A)A strong acid solution has a higher concentration than a weak acid solution.
B)A strong acid is ionized to a greater extent than a weak acid.
C)Hydrochloric acid is an example of a strong acid.
D)Acetic acid is an example of a weak acid.
E)The pH of a 0.1 M solution of acetic acid is higher than the pH of a 0.1 M solution of hydrochloric acid.

Question 21

Ammonia (NH₃) acts as a weak base in aqueous solution.What is the acid that reacts with this base when ammonia is dissolved in water?

A)None; there are no acids in pure water.
B)H₂O
C)NH₄⁺
D)OH^-
E)oxygen that always is dissolved in water

Question 22

Which of the following statements regarding the leveling effect is NOT correct?

A)All strong acids completely ionize in water and appear to have the same strength.
B)All strong bases completely hydrolyze in water and appear to have the same strength.
C)The strongest base that can exist in water is OH^-.
D)The strongest acid that can exist in water is H₃O⁺.
E)All strong acids and bases are equally strong, even in solvents other than water.

Question 23

Suppose an aqueous solution initially contains one mole of hydrochloric acid and one mole of ammonia.Which of the following statements best describes the solution once it comes to equilibrium?

A)The solution is neutral because the ammonia neutralizes the hydrochloric acid.
B)The solution is highly acidic due to the ionization of HCl: HCl(aq) $\rightarrow$ H⁺(aq) + Cl^-(aq).
C)The solution is slightly acidic due to the equilibrium NH₄⁺(aq) ⇄ NH₃ (aq) $\rightarrow$ H⁺(aq).
D)The solution is slightly basic due to the equilibrium NH₃ (aq)+ H₂O(l) ⇄ NH₄⁺ (aq) +OH^-(aq).
E)The solution is slightly basic due to the equilibrium Cl^-(aq) + H₂O(l) ⇄ HCl(aq) +OH^-(aq).

Question 24

Which of the following is a conjugate acid-base pair?

A)NaF and F^-
B)HNO₃ and HNO₂
C)HI and I^-
D)NH₄⁺ and NH₂^-
E)H₂O and H₂O₂

Question 25

In the following reaction in aqueous solution, the acid reactant is _______ and its conjugate base product is _______. CH₃ COOH(aq) +NH₃ (aq) ⇄ CH₃COO^-(aq) +NH₄ ⁺ (aq)

A)CH₃COOH; CH₃COO^-
B)CH₃COOH; NH₄⁺
C)NH₃; CH₃COO^-
D)NH₃; NH₄⁺
E)CH₃COOH; H₃O⁺

Question 26

When pure water autoionizes, which species are produced?

A)O₂^-, OH^-, H₃O⁺, and H₂O⁺
B)OH^- and H₃O⁺
C)O₂^- and H₄O₂⁺
D)H⁺ and OH^-
E)2 H⁺ and O₂^-

Question 27

Which of the following is correct?

A)K₂SO₃ is a stronger base than KHSO₃.
B)K₂CO₃ is a weaker base than KHCO₃.
C)NaHSO₃ is a stronger acid than NaHSO₄.
D)Na₂HPO₄ is a weaker base than NaH₂PO₄.
E)All of these statements are correct.

Question 28

Which of the following is NOT a conjugate acid-base pair?

A)NH₃ and NH₄⁺
B)H₃O⁺ and OH^-
C)H₂PO₄^- and HPO₄^2-
D)HS^- and H₂S
E)NH₃ and NH₂^-

Question 29

Which ending to the statement is NOT correct? The weak acid HY will be stronger than the weak acid HZ if

A)more Lewis resonance structures can be written for the Y ion than for the Z ion.
B)Y is more electronegative than Z.
C)the Y ion has more oxygen atoms than the Z ion.
D)the H-Y bond is weaker than the H-Z bond.
E)the H-Y bond is less polar than the H-Z bond.

Question 30

Which of the following cannot be a Brønsted-Lowry base?

A)OH^-
B)H₂O
C)NH₃
D)NH₄⁺
E)SH^-

Question 31

In each of the following, the stronger acid is identified and an explanation is given.All except one are correct statements.Which one is NOT correct?

A)HCl $\gt$ HF, because the HF bond energy is larger than the HCl bond energy.
B)HCO₃^- $\gt$ H₂CO_3, because the negative charge stabilizes the loss of a proton.
C)CCl₃COOH $\gt$ CH₃COOH, because electronegative substituents stabilize the conjugate base.
D)HBrO₃ $\gt$ HBrO₂, because of the additional electronegative oxygen atom.
E)ClOH $\gt$ BrOH, because Cl is more electronegative than Br.

Question 32

Which of the following is NOT correct?

A)HClO₄ is a stronger acid than HClO₃.
B)HClO is a stronger acid than HCl.
C)HClO₂ is a weaker acid than HClO₃.
D)ClO-is a stronger base than ClO₂^-.
E)ClO₂^- is a stronger base than Cl^-.

Question 33

Which of the following statements regarding acidity, basicity, pH, and pOH is NOT correct?

A)[H⁺]= [OH^-] in a neutral solution, and the pH = 7 at 25°C.
B)[H⁺] $\gt$ [OH^-] in an acidic solution, and the pH $\lt$ 7 at 25°C.
C)[H⁺] $\lt$ [OH^-] in a basic solution, and the pH $\gt$ 7 at 25°C.
D)If [H⁺] increases in a solution, [OH^-] must decrease.
E)If the pH of a solution increases, its [H⁺] increases.

Question 34

Which expression defines the autoionization constant for water, K_w?

A)[H₃O⁺][OH^-]
B)[H₂O][H₃O⁺]
C)[OH^-][H₂O]
D)[H₄O₂^-][O₂^-]
E)[H₂O][H₂O]

Question 35

Which of the following lists the conjugate acid of HAsO₄^2- first and its conjugate base second?

A)H₃O-; AsO₄^3-
B)AsO₄3-; H₂AsO₄ ^-
C)H₃AsO₄; AsO₄^3-
D)AsO₄^3-; H₃AsO₄
E)H₂AsO₄^-; AsO₄^3-

Question 36

Which of the following is a conjugate acid-base pair?

A)H₃PO₄ and HPO₄^2-
B)H₂ and H^-
C)CO₃^2-and H₂CO₃
D)OH^- and H₃O^-
E)H₂PO₄^- and PO₄^-

Question 37

In the following reaction in aqueous solution, the acid reactant is _______ and the base reactant is _______.
OH^-(aq) +C₆H₅ NH₃ ⁺(aq) ⇄ C₆ H₅ NH₂ (aq) F+H₂O(l)

A)H₂O; OH^-
B)C₆H₅NH₃^F1+; C₆H₅NH₂
C)H₂O; C₆H₅NH₂
D)C₆H₅NH₃⁺; OH^-
E)H₂O; C₆H₅NH₃⁺

Question 38

Which of the following is NOT related to the water autoionization constant, K_w?

A)[H₃O⁺] [OH^-]
B)1.0 *10^-14 at 25°C
C)2H₂O ⇄ H O⁺+OH₃^-
D)pH= 7 at 25°C
E)All are related to K_w.

Question 39

Which statement is NOT correct? Pure water at 25°C has

A)K_w = 1.0 *10^-14.
B)pOH = 7.
C)[H₃O⁺] =[OH^-].
D)pH = 7.
E)All are correct.

Question 40

Which of the following statements is NOT correct?

A)HIO is a stronger acid than HClO.
B)HClO is a stronger acid than HBrO.
C)HClO₃ is a stronger acid than HClO₂.
D)HPO₄^2- is a weaker acid than H₂PO₄ ^-.
E)H₂SO₄ is a stronger acid than H₂SO₃.

Question 41

Sometimes liquid ammonia, NH₃, is used as a solvent rather than water.Which expression defines the ammonia autoionization counterpart of K_w?

A)[H₃O⁺][OH^-]
B)[NH₃][NH₄⁺]
C)[NH₂^-][NH₄⁺]
D)[H₃O⁺][NH₂^-0]
E)[NH₄⁺][OH^-]

Question 42

When [H⁺] =1.0* 10^-7 M in water at 25°C, then

A)pH = 1.
B)pH =10^-7.
C)[OH^-] = 1.0 * 10^-7 M.
D)[OH^-] = 1.0 *10⁷ M.
E)[OH^-] = 0 M.

Question 43

When [H⁺] = 4.0 *10^-9 M in water at 25°C, then

A)pH = 9.40.
B)pH = 7.00.
C)pH= -8.40.
D)pH = 8.40.
E)pH = -9.40.

Question 44

The pH of a popular soft drink is 3.40; what is its hydronium ion concentration?

A)5.0* 10^-4 M
B)4.0 *10^-4 M
C)2.5* 10³ M
D)1.0 F* 10^-7 M
E)5.0 * 10^-5 M

Question 45

In evaluating the pH of an aqueous weak acid solution, usually can be ignored.

A)the concentration of the weak acid
B)the concentration of hydronium ions produced by the autoionization of water
C)the reaction of the weak acid with water
D)the concentration of ionized hydronium ion
E)the concentration of the conjugate base

Question 46

Boric acid is frequently used as an eyewash to treat eye infections.The pH of a 0.050 M boric acid solution is 5.28.What is the value of K_a?

A)5.3 * 10^-6
B)5.5 *10^-10
C)5.4* 10^-8
D)5.8 * 10^-4
E)5.3* 10^-12

Question 47

A solution with a pOH of 6.92 has an [OH^-] of

A)1.2 *10^-7 M.
B)9.2 * 10^-6 M.
C)6.8 * 10^-6 M.
D)7.1 M.
E)6.9 M.

Question 48

The base ionization constant K_b describes which of the following reactions for a weak base, B, in aqueous solution?

A)B(aq) + H^-(aq) ⇄ BH⁺(aq)
B)B(aq) +H₃O⁺(aq) ⇄ BH⁺(aq) + H₂O(l)
C)B(aq) + H₂O(l) ⇄ BH⁺(aq) + OH^--(aq)
D)B(aq) + OH^-(aq) ⇄ BH⁺(aq) + O^{2 -}(aq)
E)BH⁺ (aq)+OH^-(aq)⇄ B(aq) + H₂O(l)

Question 49

Pure water at any temperature has

A)a pH less than 7.
B)a pOH more than 7.
C)[H₃O+] =[OH^-].
D)pH= 7.
E)no hydronium ions in it.

Question 50

Carbon dioxide in the atmosphere in rainwater often lowers the pH to 5.0-5.6.The rainwater is

A)neutral.
B)acidic.
C)basic.
D)gray.
E)poisonous.

Question 51

A cup of coffee has a hydroxide ion concentration of 1 * 10^-10 M.What is the pH of this coffee?

A)1.0*10^-4
B)4.0
C)10.0
D)7.0
E)(-10.0)

Question 52

Suppose 0.035 moles of HCl is dissolved in enough water to produce 750 mL of solution.What is the pH?

A)pH =4.33
B)pH = 7.00
C)pH = 1.58
D)pH = -4.33
E)pH =1.33

Question 53

A 0.270 M monoprotic weak acid solution has a pH of 2.50.What is the pK_a of this acid?

A)4.43
B)1.93
C)5.57
D)9.57
E)8.07

Question 54

Suppose 0.50 L of a HNO₃ solution has a pH of 3.30.How many moles of HNO₃ must have been initially dissolved in the solution?

A)2.5 *10^-4 moles
B)5.0 *10^-4 moles
C)1.7 * 10^-3 moles
D)1.0 * 10^-3 moles
E)1.8 * 10^-2 moles

Question 55

A solution with a pOH of 11.70 has an [H⁺] of

A)2.0 *10^-12 M.
B)3.2 *10^-4 M.
C)0.36 M.
D)5.0 * 10^-3 M.
E)2.30 M.

Question 56

A solution with a pH of 9.50 has a pOH of

A)9.50.
B)0.50.
C)4.50.
D)23.5.
E)19.0.

Question 57

The pH of a 0.250 M hypoiodous (HOI) solution is 5.620.What is the value of K_a?

A)5.76* 10^-12
B)2.40 * 10^-6
C)2.30 *10^-11
D)4.17* 10^-9
E)6.95 *10^-17

Question 58

The acid ionization equilibrium constant, K_a, describes which of the following reactions where HA is a generic weak acid)?

A)HA(aq) +OH sup>- (aq) → H₂O(l) + A^-(aq)
B)HA(aq) + H₂O(l) → H₃O⁺(aq) + A^-(aq)
C)HA(aq) + H₃ O⁺(aq) → H₂ A⁺(aq) + H₂ O(l)
D)HA(aq) + H₂ A⁺(aq) → H₂ A⁺(aq) +HA(aq)
E)H₃O⁺(aq) +A^-(aq) → HA(aq) + H₂O(l)

Question 59

Which of the following shows a relationship expressed in the correct number of significant figures?

A)[H⁺] = 1.270*10^-2 M; pH =1.896
B)pH = 2.273; [H⁺] = 5.333 *10^-3 M
C)[H⁺] = 1.80 *10^-2 M; pH = 1.74
D)pH =8.9; [H⁺] = 1.3*10^-9 M
E)pH =4.0; [H⁺] = 1 *10^-4 M

Question 60

In an experiment, 0.438 L of 0.152 M NaOH is diluted with water to a final volume of 3.00 L.What is the pH of the dilute solution?

A)1.654
B)13.182
C)1.295
D)12.705
E)12.346

Question 61

What is the hydronium ion concentration of a 0.20 M diethylamine solution? (K_b value for diethylamine = 8.6*10^-4)

A)1.2 *10^-11 M
B)6.6 * 10^-9 M
C)1.5 *10^-6 M
D)7.6* 10^-13 M
E)1.3 *10^-2 M

Question 62

What is the pH of a 0.0250 M BaOH)₂ solution?

A)1.602
B)1.301
C)11.004
D)12.398
E)12.700

Question 63

What is the hydronium ion concentration of a 0.010 M acetic acid solution? (K_a for acetic acid = 1.76 *10^-5)

A)1.8 * 10^-3
B)1.8 * 10^-5
C)1.0 * 10^-2
D)1.8 * 10^-7
E)4.2 *0^-4

Question 64

Piperidine, C₅H₁₁N, is a weak base in water.If a 0.120 M piperidine solution has a pH of 12.077, what is the K_b of piperidine?

A)4.78 *10^-2
B)2.98* 10^-3
C)1.19 * 10^-3
D)1.31 * 10^-3
E)6.98 * 10^-12

Question 65

What is the percent dissociation of 0.40 M butyric acid (HC₄H₇O₂)? (The K_a value for butyric acid is 1.48 * 10^-5.)

A)0.24%
B)0.96%
C)6.1 * 10^-3%
D)3.7*10^-3%
E)0.61%

Question 66

The concentration of acetic acid (pK_a = 4.75) in vinegar is about 1.0 M.With this information, what do you predict the pH of vinegar to be?

A)4.75
B)2.38
C)11.62
D)7.00
E)5.35

Question 67

What is the pH of a 0.45 M solution of aniline (C₆H₅NH₂)? (pK_b =9.40)

A)2.47
B)9.13
C)9.85
D)4.87
E)11.53

Question 68

What is the pH of a 0.20 M ammonia solution? (K_b value for ammonia = 1.8 *10^-5)

A)11.28
B)9.26
C)4.74
D)9.56
E)2.72

Question 69

What is the pH of a 16.0 M HCl solution?

A)1.204
B)(-1.204)
C)0.000
D)12.796
E)15.204

Question 70

What is the percent dissociation of 0.20 M iodic acid? (The K_a value for iodic acid, HIO₃, is 1.7 *10^-1.)

A)59%
B)85%
C)92%
D)12%
E)18%

Question 71

What is the pH of a solution prepared by dissolving 0.025 mol of NaOH in 450.0 mL of solution?

A)1.26
B)12.40
C)4.26
D)9.74
E)12.74

Question 72

What is the pH of a 0.010 M acetic acid solution? (K_a for acetic acid = 1.76 *10^-5)

A)2.00
B)4.74
C)2.74
D)3.38
E)6.74

Question 73

What is the percent dissociation of 0.150 M triethylamine? (The K_b value for triethylamine is 5.25 * 10^-4.)

A)5.92%
B)5.75 *10^-3%
C)39.4%
D)5.90 *10^-3%
E)5.75%

Question 74

The first disinfectant used by Joseph Lister was called carbolic acid.This substance now is known as phenol, C₆H₅OH (pK_a = 9.90).What is the pH of a 0.10 M solution of phenol?

A)3.50
B)8.55
C)6.50
D)5.45
E)4.50

Question 75

The degree of ionization

A)increases with increasing concentration of a weak acid.
B)decreases with increasing concentration of a weak acid.
C)does not change with changing concentration of a weak acid.
D)is not related to the concentration of a weak acid.
E)is independent of the composition of the weak acid.

Question 76

What is the pH of a 0.025 M pyridine solution? (K_b value for pyridine =1.7 *10^-9)

A)7.17
B)12.40
C)8.81
D)5.19
E)10.37

Question 77

What is the pH of a 0.0250 M HNO₃ solution?

A)1.602
B)(-1.602)
C)0.000
D)12.398
E)2.500

Question 78

What is the concentration of [OH^-] in a 0.20 M ammonia solution? (K_b value for ammonia =1.8 *10^-5)

A)3.6 * 10^-6 M
B)1.8 *10^-5 M
C)0.20 M
D)1.9 *10^-3 M
E)4.2 *10^-4 M

Question 79

Codeine (C₁₈H₂₁NO₃, 299.36 g/mol) is a weak base.Suppose a 2.00 g pain tablet containing 30.0 mg of codeine is dissolved in water to produce a 0.100 L solution with a pH of 9.47.Based on this information, determine the value of K_b for codeine.

A)8.6 *10^-6
B)3.4 * 10^-9
C)9.0 *10^-7
D)2.9 *10^-2
E)8.7 *10^-7

Question 80

The acidic ingredient in vinegar is acetic acid.If the pH of a particular brand of vinegar is 2.40 and the molar concentration of acetic acid in the vinegar is 0.85 M, determine the value of K_a for acetic acid.

A)2.5 * 10^-5
B)5.0 * 10^-5
C)4.7 * 10^-3
D)1.9 *10^-5
E)7.4 *10^-3