Deck 16: Acid-Base Equilibria

Question 1

A 8.0 × 10^-3 M solution of acetic acid,HC₂H₃O₂,is 4.7% ionized at 25°C.In a 8.0 × 10^-4 M solution,the percentage of ionization would be

A)100%.
B)<4.7%.
C)>4.7%.
D)the same.
E)zero.

Answer 1

>4.7%.

Question 2

For which of the following equilibria does K_c correspond to the acid-ionization constant,K_a,of HC₂O₄^-?

A)HC₂O₄^-(aq)+ H₂O(l) H₂C₂O₄(aq)+ OH^-(aq)
B)H₂C₂O₄(aq)+ H₂O(l) H₃O⁺(aq)+ HC₂O₄^-(aq)
C)HC₂O₄^-(aq)+ H₂O(l) H₃O⁺(aq)+ C₂O₄^2-(aq)
D)HC₂O₄^-(aq)+ OH^-(aq) C₂O₄^2-(aq)+ H₂O(l)
E)HC₂O₄^-(aq)+ H₃O⁺(aq) H₂C₂O₄(aq)+ H₂O(l)

Answer 2

HC₂O₄^-(aq)+ H₂O(l) H₃O⁺(aq)+ C₂O₄^2-(aq)

Question 3

Consider the K_a values for the following acids:
Cyanic acid,HOCN,3.5 × 10^-4
Formic acid,HCHO₂,1.7 × 10^-4
Lactic acid,HC₃H₅O₃,1.3 × 10^-4
Propionic acid,HC₃H₅O₂,1.3 × 10^-5
Benzoic acid,HC₇H₅O₂,6.3 × 10^-5
Which has the strongest conjugate base?

A)propionic acid
B)benzoic acid
C)lactic acid
D)formic acid
E)cyanic

Answer 3

propionic acid

Question 4

Consider the K_a values for the following acids:
Cyanic acid,HOCN,3.5 × 10^-4
Formic acid,HCHO₂,1.7 × 10^-4
Lactic acid,HC₃H₅O₃,1.3 × 10^-4
Propionic acid,HC₃H₅O₂,1.3 × 10^-5
Benzoic acid,HC₇H₅O₂,6.3 × 10^-5
Given initially equimolar soutions of each weak acid,which solution will have the highest hydronium ion concentration once equilibrium is established?

A)cyanic acid
B)benzoic acid
C)lactic acid
D)formic acid
E)propionic acid

Question 5

A 0.10 M aqueous solution of a weak acid HA has a pH of 5.00.What is the value of K_a for HA?

A)1.0 × 10^-8
B)1.0 × 10^-6
C)1.0 × 10^-7
D)1.0 × 10^-5
E)1.0 × 10^-9

Question 6

For which of the following equilibria does K_c correspond to an acid-ionization constant,K_a?

A)NH₃(aq)+ H₃O⁺(aq) NH₄⁺(aq)+ H₂O(l)
B)NH₄⁺(aq)+ OH^-(aq) NH₃(aq)+ H₂O(l)
C)F^-(aq)+ H₂O(l) HF(aq)+ OH^-(aq)
D)HF(aq)+ OH^-(aq) H₂O(l)+ F^-(aq)
E)NH₄⁺(aq)+ H₂O(l) NH₃(aq)+ H₃O⁺(aq)

Question 7

For the equilibrium that exists in an aqueous solution of nitrous acid (HNO₂,a weak acid),the equilibrium-constant expression is

A)K = .
B)K = .
C)K = .
D)K = [H⁺][NO₂^-].
E)none of these

Question 8

For which of the following equilibria does K_c correspond to the acid-dissociation constant,K_a,of H₂PO₄^-?

A)H₂PO₄^-(aq)+ H₃O⁺(aq) H₃PO₄(aq)+ H₂O(l)
B)H₂PO₄^-(aq)+ H₂O(l) H₃PO₄(aq)+ OH^-(aq)
C)H₂PO₄^-(aq)+ H₂O(l) H₃O⁺(aq)+ HPO₄^2-(aq)
D)H₃PO₄(aq)+ H₂O(l) H₃O⁺(aq)+ H₂PO₄^-(aq)
E)HPO₄^2-(aq)+ H₂O(l) H₂PO₄^-(aq)+ OH^-(aq)

Question 9

Rank acetic acid (HC₂H₃O₂),hydrocyanic acid (HOCN),and hydrofluoric acid (HF)in order of increasing strength.
Acid
K_a
HC₂H₃O₂
1)8 × 10^-5
HOCN
3)5 × 10^-4
HF
6)8 × 10^-4

A)HC₂H₃O₂ < HOCN < HF
B)HOCN < HC₂H₃O₂ < HF
C)HOCN < HF < HC₂H₃O₂
D)HF < HOCN < HC₂H₃O₂
E)HF < HC₂H₃O₂ < HOCN

Question 10

What is the equilibrium expression for the equilibrium A^-(aq)+ H₃O⁺(aq) HA(aq)+ H₂O(l)?

A)
B)
C)
D)
E)K_b

Question 11

What is the percent ionization of a 1.5 M HC₂H₃O₂ solution (K_a = 1.8 × 10^-5 )at 25°C?
+

A)0.52 %
B)0.35 %
C)2.5 %
D)0.18 %
E)0.28 %

Question 12

A 0.010 M aqueous solution of a weak acid HA has a pH of 4.0.What is the degree of ionization of HA in the solution?

A)0.1 %
B)0.01 %
C)0.001 %
D)1 %
E)10 %

Question 13

For which of the following equilibria does K_c correspond to the acid-ionization constant,K_a,of HCO₃^-?

A)HCO₃^-(aq)+ OH^-(aq) CO₃^2-(aq)+ H₂O(l)
B)H₂CO₃(aq)+ H₂O(l) HCO₃^-(aq)+ H₃O⁺(aq)
C)HCO₃^-(aq)+ H₂O(l) H₂CO₃(aq)+ OH^-(aq)
D)HCO₃^-(aq)+ H₃O⁺(aq) H₂CO₃(aq)+ H₂O(l)
E)HCO₃^-(aq)+ H₂O(l) CO₃^2-(aq)+ H₃O⁺(aq)

Question 14

A 0.10 M solution of a weak monoprotic acid has a hydronium-ion concentration of 7.2 × 10^-4 M.What is the acid-ionization constant,K_a,for this acid?

A)2.7 × 10^-2
B)6.3 × 10^-3
C)7.2 × 10^-4
D)5.2 × 10^-6
E)8.6 × 10^-5

Question 15

An initially 1.0 M aqueous solution of a weak monoprotic acid has a total ion concentration of M when equilibrium is established.What is the acid-ionization constant,K_a,of the weak acid? (assume C_a/K_a ≥ 10²)

A)
B)
C)
D)
E)

Question 16

At a temperature of 25°C an initally 0.011 M solution of a weak monoprotic acid is 2.9 % ionized once equilibrium is established.What is the acid-ionization constant,K_a,for this acid? (assume C_a/K_a ≥ 10²)

A)
B)
C)
D)
E)

Question 17

What is the pH of an initially 0.428 M solution of a weak monoprotic acid that is 0.11 % ionized when equilibrium is established? (assume C_a/K_a ≥10²)

A)3.32
B)7.00
C)1.32
D)10.63
E)10.68

Question 18

Equal moles of the indicated acids are dissolved in the amounts of water shown in the beakers below.In which solution will the percent ionization of the acid be the lowest?

A)All have equal percent ionization of acid.
B)III
C)IV
D)II
E)I

Question 19

A 0.10 M solution of a weak monoprotic acid has a pH of 3.40 at 25°C.What is the acid-ionization constant,K_a,for this acid?

A)1.6 × 10^-6
B)4.0 × 10^-4
C)3.4 × 10^-5
D)1.2 × 10^-3
E)1.8 × 10^-7

Question 20

A 0.20 M solution of a weak monoprotic acid is 0.22 % ionized.What is the acid-ionization constant,K_a,for this acid?

A)1.9 × 10^-6
B)2.2 × 10^-6
C)1.1 × 10^-4
D)2.4 × 10^-5
E)9.7 × 10^-7

Question 21

What is the equilibrium hydronium ion concentration of an initially 4.5 M solution of hypoiodous acid,HOI,at 25°C (K_a = )?

A) M
B) M
C) M
D) M
E) M

Question 22

What is the equilibrium pH of an initially 0.73 M solution of the monoprotic acid benzoic acid at 25°C (K_a = )?

A)2.17
B)7.00
C)1.87
D)12.13
E)5.13

Question 23

What is the equilibrium percent ionization of an initially 0.32 M solution of the monoprotic acid valeric acid,HC₅H₉O₂,at 25°C (K_a = )?

A)0.67%
B)1.30%
C)0.0014%
D)0.1%
E)2.00%

Question 24

In a 0.20 M solution of a diprotic acid H₂A (Ka₁ = 1.3 × 10^-5 and Ka₂ = 2.7 × 10^-10 at 25°C),what is the equilibrium concentration of A^2-?

A)7.3 × 10^-6 M
B)2.7 × 10^-10 M
C)1.6 × 10^-3 M
D)0.40 M
E)0.20 M

Question 25

What is K_a for a weak monoprotic acid if a 0.020 M solution of the acid has a pH of 3.28 at 25°C?

A)5.2 × 10^-2
B)1.4 × 10^-5
C)7.1 × 10^-2
D)1.0 × 10^-6
E)2.8 × 10^-4

Question 26

In a 0.01 M solution of 1,4-butanedicarboxylic acid,HOOCCH₂CH₂COOH (Ka₁ = 2.9 × 10^-5,Ka₂ = 5.3 × 10^-6),which species is present in the lowest concentration?

A)(^-OOCCH₂CH₂COO^-)(aq)
B)H₂O
C)HOOCCH₂CH₂COO^-(aq)
D)H₃O⁺(aq)
E)HOOCCH₂CH₂COOH(aq)

Question 27

What is the pH of a solution prepared by dissolving 0.0163 mol of chloroacetic acid,(HC₂H₂O₂Cl)in 1.30 L of water? For chloroacetic acid,K_a = 1.4 × 10^-3.

A)1.90
B)2.45
C)11.55
D)12.10
E)2.38

Question 28

In a 0.01 M solution of 1,4-butanedicarboxylic acid,HOOCCH₂CH₂COOH (Ka₁ = 2.9 × 10^-5,Ka₂ = 5.3 × 10^-6),which species is present in the highest concentration?

A)HOOCCH₂CH₂COO^-(aq)
B)HOOCCH₂CH₂COOH(aq)
C)H₃O⁺(aq)
D)(^-OOCCH₂CH₂COO^-)(aq)
E)OH^-(aq)

Question 29

What is the equilibrium pH of an initially 4.4 M solution of hypochlorous acid,HOCl,at 25°C (K_a = )?

A)3.44
B)7.37
C)10.41
D)10.71
E)4.08

Question 30

Carbonic acid,H₂CO₃,is a weak diprotic acid.In a 0.1 M solution of the acid,which of the following species is present in the largest amount?

A)HCO₃^-
B)CO₃^2-
C)H₂CO₃
D)H₃O⁺
E)OH^-

Question 31

Phosphoric acid,H₃PO₄,will undergo three successive ionization reactions to varying extents in water.What is the balanced equilibrium identified as K_a3?

A)H₂PO₄^-(aq)+ H₂O(l) H₃O⁺(aq)+ HPO₄^2-(aq)
B)HPO₄^2-(aq)+ H₂O(l) PO₄^3-(aq)+ H₃O⁺(aq)
C)H₂PO₄^-(aq)+ H₃O⁺(aq) H₃PO₄(aq)+ H₂O(l)
D)H₃PO₄(aq)+ H₂O(l) H₃O⁺(aq)+ H₂PO₄^-(aq)
E)PO₄^3-(aq)+ H₂O(l) HPO₄^2-(aq)+ OH^-(aq)

Question 32

For a 0.05 M H₂SO₃ solution,which of the following relationships is true?

A)[SO₃^2-] > [H₂SO₃]
B)[SO₃^2-] > [HSO₃^-]
C)[HSO₃^-] > [H₂SO₃]
D)[H₂SO₃] > [H⁺]
E)[H⁺] > [H₂SO₃]

Question 33

A 8.42-g sample of homogentisic acid,a weak organic acid having K_a = 4.0 × 10^-5,is dissolved in 35.00 mL of water and its pH is measured to be 2.122.What is the molar mass of homogentisic acid?

A)168 g/mol
B)1110 g/mol
C)1.43 g/mol
D)5.88 g/mol
E)240 g/mol

Question 34

What is the equilibrium concentration of chloroacetic acid,HC₂H₂O₂Cl,in a solution prepared by dissolving 0.0271 mol of HC₂H₂O₂Cl in 1.50 L of water? For chloroacetic acid,K_a = 1.4 × 10^-3.

A)4.38 × 10^-3 M
B)1.81 × 10^-2 M
C)5.03 × 10^-3 M
D)1.37 × 10^-2 M
E)9.03 × 10^-3 M

Question 35

Which of the following represents the usual relationship of acid-ionization constants for a triprotic acid?

A)
B)
C)
D)
E)

Question 36

It is safe to make the simplifying assumption that x can be neglected in the denominator of the equilibrium equation when

A) .
B) .
C) .
D) .
E) .

Question 37

What is the percent ionization of a solution prepared by dissolving 0.0175 mol of chloroacetic acid,(HC₂H₂O₂Cl)in 1.30 L of water? For chloroacetic acid,K_a = 1.4 × 10^-3.

A)1.3 %
B)100 %
C)27 %
D)72 %
E)0.36 %

Question 38

For a 0.10 M solution of glutaric acid,HO₂C(CH₂)₃CO₂H (Ka₁ = 4.6 × 10^-5,Ka₂ = 3.9 × 10^-6),rank the following species in order of increasing equilibrium concentration.

A)H₃O⁺ < ^-O₂C(CH₂)₃COO^- < HO₂C(CH₂)₃COO^- < OH^- < HO₂C(CH₂)₃CO₂H
B)OH^- < ^-O₂C(CH₂)₃COO^- < H₃O⁺ < HO₂C(CH₂)₃COO^- < HO₂C(CH₂)₃CO₂H
C)OH^- < ^-O₂C(CH₂)₃COO^- < HO₂C(CH₂)₃COO^- < H₃O⁺ < HO₂C(CH₂)₃CO₂H
D)H₃O⁺ < HO₂C(CH₂)₃CO₂H < HO₂C(CH₂)₃COO^- < ^-O₂C(CH₂)₃COO^- < OH^-
E)OH^- < ^-O₂C(CH₂)₃COO^- < HO₂C(CH₂)₃COO^- < HO₂C(CH₂)₃CO₂H < H₃O⁺

Question 39

What is the hydronium-ion concentration of a 0.30 M solution of HCN (K_a = 4.9 × 10^-10)at 25°C?

A)1.7 × 10^-4 M
B)3.4 × 10^-6 M
C)2.2 × 10^-6 M
D)1.2 × 10^-5 M
E)4.0 × 10^-5 M

Question 40

The equilibrium hydronium ion concentration of an initially 0.655 M solution of a monoprotic weak acid is M.The acid dissociation constant is
At 25°C.What is the pH of this solution?

A)2.26
B)7.00
C)11.74
D)4.52
E)0.18

Question 41

What is the hydronium-ion concentration of a 0.210 M oxalic acid,H₂C₂O₄,solution? For oxalic acid,Ka₁ = 5.6 × 10^-2 and Ka₂ = 5.1 × 10^-5.

A)8.4 × 10^-2 M
B)1.1 × 10^-1 M
C)1.0 × 10^-7 M
D)3.2 × 10^-3 M
E)3.3 × 10^-3 M

Question 42

Which of the following reactions is associated with the definition of K_b?

A)CN^-(aq)+ H⁺(aq) HCN(aq)
B)F^-(aq)+ H₂O(l) HF(aq)+ OH^-(aq)
C)Zn(OH₂)₆²⁺(aq) [Zn(OH₂)₅OH]⁺(aq)+ H⁺(aq)
D)Cr³⁺(aq)+ 6H₂O(l) Cr(OH₂)₆³⁺(aq)
E)none of these

Question 43

What is the pH of a 0.35 M solution of methylamine (CH₃NH₂,K_b = 4.4 × 10^-4)at 25^oC?

A)5.55
B)0.46
C)12.09
D)13.54
E)1.91

Question 44

What is the concentration of C₂O₄^2- in a 0.370 M oxalic acid,H₂C₂O₄,solution? For oxalic acid,Ka₁ = 5.6 × 10^-2 and Ka₂ = 5.1 × 10^-5.

A)1.2 × 10^-1 M
B)-3 × 10^-3 M
C)4.3 × 10^-3 M
D)5.1 × 10^-5 M
E)1.4 × 10^-1 M

Question 45

What is the concentration of HC₂O₄^- in a 0.300 M oxalic acid,H₂C₂O₄,solution? For oxalic acid,Ka₁ = 5.6 × 10^-2 and Ka₂ = 5.1 × 10^-5.

A)3.9× 10^-3 M
B)1.0 × 10^-1 M
C)1.3 × 10^-1 M
D)3.9 × 10^-3 M
E)5.1 × 10^-5 M

Question 46

What is the equilibrium concentration of H₂C₂O₄ in a 0.370 M oxalic acid,H₂C₂O₄,solution? For oxalic acid,Ka₁ = 5.6 × 10^-2 and Ka₂ = 5.1 × 10^-5.

A)2.5 × 10^-1 M
B)1.4 × 10^-1 M
C)3.7 × 10^-1 M
D)5.1 × 10^-5 M
E)1.2 × 10^-1 M

Question 47

A solution of aniline (C₆H₅NH₂,K_b = 4.2 × 10^-10)has a pH of 8.56 at 25^oC.What was the initial concentration of aniline?

A)2.8 × 10^-9 M
B)2.1 × 10^-8 M
C)3.2 × 10^-2 M
D)4.2 × 10^-10 M
E)3.6 × 10^-6 M

Question 48

What is the concentration of HCO₃^- in a 0.010 M solution of carbonic acid,H₂CO₃? For carbonic acid,Ka₁ = 4.2 × 10^-7 and Ka₂ = 4.8 × 10^-11.

A)6.5 × 10^-5 M
B)1.0 × 10^-2 M
C)3.2 × 10^-5 M
D)4.8 × 10^-11 M
E)4.2 × 10^-7 M

Question 49

What is the percent ionization at equilibrium in a 0.10 M solution of dimethylamine,(CH₃)₂NH (K_b = 5.1 × 10^-4),at 25^oC?

A)6.8%
B)0.51%
C)0.68%
D)100%
E)10%

Question 50

What is the hydroxide-ion concentration of a 0.150 M oxalic acid,H₂C₂O₄,solution? For oxalic acid,Ka₁ = 5.6 × 10^-2 and Ka₂ = 5.1 × 10^-5.

A)3.6 × 10^-12 M
B)1.1 × 10^-13 M
C)2.7 × 10^-3 M
D)1.5 × 10^-13 M
E)1.0 × 10^-7 M

Question 51

For which of the following equilibria does K_c correspond to the base-ionization constant,K_b,of HCO₃^-?

A)HCO₃^-(aq)+ H₂O(l) CO₃^2-(aq)+ H₃O⁺(aq)
B)HCO₃^-(aq)+ H₂O(l) H₂CO₃(aq)+ OH^-(aq)
C)H₂CO₃(aq)+ H₂O(l) HCO₃^-(aq)+ H₃O⁺(aq)
D)HCO₃^-(aq)+ OH^-(aq) CO₃^2-(aq)+ H₂O(l)
E)HCO₃^-(aq)+ H₃O⁺(aq) H₂CO₃(aq)+ H₂O(l)

Question 52

What is the hydronium-ion concentration at equilibrium in a 0.10 M solution of aniline (C₆H₅NH₂,K_b = 4.2 × 10^-10)at 25^oC?

A)1.0 × 10^-13 M
B)1.0 × 10^-1 M
C)1.5 × 10^-9 M
D)6.5 × 10^-6 M
E)6.5 × 10^-5 M

Question 53

What is the equilibrium concentration of ammonium ion in a 0.33 M solution of ammonia (NH₃,K_b = 1.8 × 10^-5)at 25^oC?

A)3.0 × 10^-14 M
B)4.1 × 10^-12 M
C)2.4 × 10^-3 M
D)7.4 × 10^-3 M
E)3.3 × 10^-1 M

Question 54

What is the hydroxide-ion concentration at equilibrium in a 0.66 M solution of ethylamine (C₂H₅NH₂,K_b = 4.7 × 10^-4)at 25^oC?

A)1.7 × 10^-2 M
B)2.7 × 10^-2 M
C)1.5 × 10^-14 M
D)5.8 × 10^-13 M
E)6.6 × 10^-1 M

Question 55

What is the pOH of a 0.17 M solution of pyridine (K_b = 1.4 × 10^-9)at 25°C?

A)1.54
B)4.04
C)8.85
D)4.81
E)11.08

Question 56

For which of the following equilibria does K_c correspond to a base-ionization constant,K_b?

A)H₃O⁺(aq)+ OH^-(aq) 2H₂O(l)
B)HCO₃^-(aq)+ OH^-(aq) CO₃^2-(aq)+ H₂O(l)
C)HOCl(aq)+ H₂O(l) H₃O⁺(aq)+ OCl^-(aq)
D)CO₃^2-(aq)+ H₂O(l) HCO₃^-(aq)+ OH^-(aq)
E)HCHO₂(aq)+ NH₃(aq) CHO₂^-(aq)+ NH₄⁺(aq)

Question 57

The equilibrium hydronium ion concentration of an initially 0.510 M solution of a diprotic weak acid (H₂A)is M.What is K_a1? (assume C_a/K_a ≥ 10² and K_a1 >> K_a2)

A)
B)
C)
D)
E)not enough information provided

Question 58

What is the hydronium-ion concentration in a 0.018 M solution of carbonic acid,H₂CO₃? For carbonic acid,Ka₁ = 4.2 × 10^-7 and Ka₂ = 4.8 × 10^-11.

A)1.8 × 10^-2 M
B)4.2 × 10^-7 M
C)4.8 × 10^-11 M
D)8.7 × 10^-5 M
E)4.3 × 10^-5 M

Question 59

What is the concentration of CO₃^2- in a 0.033 M solution of carbonic acid,H₂CO₃? For carbonic acid,Ka₁ = 4.2 × 10^-7 and Ka₂ = 4.8 × 10^-11.

A)3.3 × 10^-2 M
B)1.2 × 10^-4 M
C)5.9 × 10^-5 M
D)4.8 × 10^-11 M
E)4.2 × 10^-7 M

Question 60

What is the base-ionization equilibrium constant for an aqueous solution of ammonia,NH₃?

A)
B)
C)
D)
E)none of these

Question 61

Which of the following equilibria best represents the hydrolysis reaction that occurs in an aqueous solution of NH₄Cl?

A)Cl^-(aq)+ H₃O⁺(aq) HCl(aq)+ H₂O(l)
B)NH₄⁺(aq)+ H₂O(l) NH₃(aq)+ H₃O⁺(aq)
C)NH₄⁺(aq)+ OH^-(aq) NH₃(aq)+ H₂O(l)
D)Cl^-(aq)+ H₂O(l) HCl(aq)+ OH^-(aq)
E)NH₄⁺(aq)+ Cl^-(aq) NH₄Cl(s)

Question 62

Saccharin is a weak organic base with a K_b of 4.80 × 10^-3.A 0.297-g sample of saccharin dissolved in 25.0 mL of water has a pH of 12.190.What is the molar mass of saccharin?

A)0.823 g/mol
B)33.700 g/mol
C)6.824090785E+24 g/mol
D)185 g/mol
E)278 g/mol

Question 63

What is K_b for the following equilibrium? K_a for HNO₂ is 5.0 × 10^-4.
NO₂^-(aq)+ H₂O(l)
HNO₂(aq)+ OH^-(aq)

A)2.0 × 10^-4
B)5.0 × 10^-4
C)5.0 × 10¹⁰
D)5.0 × 10¹⁸
E)2.0 × 10^-11

Question 64

Which of the following salts is most likely to form an aqueous solution having the pH shown in the figure below?

A)KCl
B)Zn(NO₃)₂
C)NaCN
D)NH₄Cl
E)LiBr

Question 65

The K_a for hydrofluoric acid is 6.8 × 10^-4.What is K_b for the fluoride ion?

A)1.5 × 10^-11
B)6.8 × 10^-4
C)1.5 × 10³
D)6.8 × 10¹⁰
E)6.8 × 10^-18

Question 66

Consider the reaction NH₃(aq)+ H₂O(l) NH₄⁺(aq)+ OH^-(aq).K_b for NH₃ is 1.8 × 10^-5 at 25°C.What is K_a for the NH₄⁺ ion at 25°C?

A)5.6 × 10⁴
B)5.6 × 10^-10
C)1.8 × 10^-5
D)7.2 × 10^-12
E)9.2 × 10^-8

Question 67

Which of the following salts is most likely to form an aqueous solution having the pH shown in the figure below?

A)Na₂CO₃
B)RbF
C)NH₄Cl
D)Zn(NO₃)₂
E)KCl

Question 68

What is K_a at 25°C for the following equilibrium?
CH₃NH₃⁺(aq)+ H₂O(l)
CH₃NH₂(aq)+ H₃O⁺(aq)
K_b (CH₃NH₂)= 4.4 × 10^-4 at 25°C.

A)4.4 × 10^-4
B)2.3 × 10³
C)4.4 × 10^-10
D)4.4 × 10⁴
E)2.3 × 10^-11

Question 69

Which of the following salts is most likely to form an aqueous solution having the pH shown in the figure below?

A)NH₄Cl
B)NaBr
C)K₂CO₃
D)RbCN
E)LiNO₃

Question 70

Which of the following statements is true concerning a 0.1 M solution of Na₂S and a 0.1 M solution of NaHS? For H₂S,Ka₁ = 1.0 × 10^-7 and Ka₂ = 1.3 × 10^-13.

A)Both solutions are neutral.
B)The sodium hydrogen sulfide solution is the more basic.
C)Both solutions have the same pH.
D)The sodium sulfide solution is the more basic.
E)Both the solutions are acidic.

Question 71

Which of the following solutions has the highest hydroxide-ion concentration?

A)0.10 M NH₄ClO₄
B)0.10 M NaI
C)0.10 M NaNO₃
D)0.10 M NH₄Cl
E)0.10 M NaCN

Question 72

Given the following,what will be the approximate equilibrium pH of an aqueous solution of ammonium cyanide,NH₄CN?
NH₄⁺
K_a = 5.69 x10^-10
HCN
K_a = 6.2 x10^-10

A)slightly basic
B)slightly acidic
C)nearly neutral

Question 73

Given the following,what will be the approximate equilibrium pH of an aqueous solution of ammonium acetate,NH₄CH₃CO₂?
NH₄⁺
K_a = 5.69 x10^-10
CH₃CO₂^-
K_b = 5.71 x10^-10

A)very basic
B)very acidic
C)nearly neutral

Question 74

Which of the following salts will produce a neutral solution when added to pure water?

A)LiHCO₃
B)NH₄NO₃
C)Na₂SO₄
D)RbNO₂
E)KNO₃

Question 75

The amphiprotic anion monohydrogenphosphate acts as both an acid and a base in aqueous solution.Given the following acid-ionization and base-hydrolysis constants,what will be the approximate equilibrium pH of an aqueous solution of sodium monohydrogenphosphate?
K_a =
K_b =
​

A)basic
B)acidic
C)neutral

Question 76

A 0.0678 M solution of a weak base has a pH of 9.44.What is the identity of the weak base?
Weak Base
K_b
Ethylamine (CH₃CH₂NH₂)
4)7 × 10^-4
Hydrazine (N₂H₄)
1)7 × 10^-6
Hydroxylamine (NH₂OH)
1)1 × 10^-8
Pyridine (C₅H₅N)
1)4 × 10^-9
Aniline (C₆H₅NH₂)
4)2 × 10^-10

A)hydrazine
B)pyridine
C)ethylamine
D)hydroxylamine
E)aniline

Question 77

What is K_a for the anilinium cation,C₆H₅NH₃⁺,at 25°C? (K_b for C₆H₅NH₂ = 4.2 × 10^-10 at 25°C.)

A)1.0 × 10^-7
B)4.2 × 10⁴
C)4.2 × 10^-24
D)2.4 × 10^-5
E)4.2 × 10^-10

Question 78

Which of the following salts forms an acidic aqueous solution?

A)NaNO₂
B)KCH₃CO₂
C)Rb₂O
D)FeCl₃
E)NaCN

Question 79

Which of the following salts will produce an acidic solution when added to pure water?

A)Cs₂CO₃
B)NaF
C)KCN
D)Al(NO₃)₃
E)Li₂S

Question 80

Which of the following equilibria best represents the hydrolysis reaction that occurs in an aqueous solution of KNO₂?

A)NO₂^-(aq)+ H₂O(l) HNO₃(aq)+ 2H⁺(aq)
B)NO₂^-(aq)+ H₂O(l) HNO₂(aq)+ OH^-(aq)
C)NO₂^-(aq)+ H₃O⁺(aq) HNO₂(aq)+ H₂O(l)
D)K⁺(aq)+ NO₂^-(aq)+ H₂O(l) KOH(aq)+ HNO₂(aq)
E)K⁺(aq)+ H₂O(l) KOH(aq)+ H⁺(aq)