Deck 14: Acids and Bases

Question 1

True or false: The species Cl^- is not a good base in aqueous solution.

A)True.This is because Cl^- is the conjugate base of a weak acid.
B)False.The species Cl^- is a good base in aqueous solution because it is the conjugate base of a strong acid.
C)True.This is because Cl^- is a good proton donor.
D)False.The species Cl^- is a good base in aqueous solution because of its high electronegativity.
E)True.This is because water has a stronger attraction for protons than does Cl^-.

Answer 1

True.This is because water has a stronger attraction for protons than does Cl^-.

Question 2

Consider the following reactions:
a)Al³⁺ + 6H₂O Al(OH₂)₆³⁺
b)Al(OH₂)₆³⁺ Al(OH)(OH₂)₅²⁺ + H⁺
c)OCl^- + H₂O HOCl + OH^-
d)CN^- + H⁺ HCN
e)none of these
Which is associated with the definition of K_a?

A)a
B)b
C)c
D)d
E)e

Answer 2

b

Question 3

Which of the following is not true for a solution at 25°C that has a hydroxide concentration of 2.5 $\times$ 10^-6 M?

A)K_w = 1 $\times$ 10^-14
B)The solution is acidic.
C)The solution is basic.
D)The [H⁺] is 4.0 $\times$ 10^-9 M.
E)The K_w is independent of what the solution contains.

Answer 3

The solution is acidic.

Question 4

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 = [H⁺][NO₂^-]
D)K =
E)none of these

Question 5

The equilibrium constants (K_a)for HCN and HF in H₂O at 25°C are 6.2 $\times$ 10^-10 and 7.2 $\times$ 10^-4,respectively.The relative order of base strengths is:

A)F^- > H₂O > CN^-
B)H₂O > F^- > CN^-
C)CN^- > F^- > H₂O
D)F^- > CN^- > H₂O
E)none of these

Question 6

The autoionization of water,as represented by the below equation,is known to be endothermic.Which of the following correctly states what occurs as the temperature of water is raised? H₂O(l)+ H₂O(l) H₃O⁺(aq)+ OH^-(aq)

A)The pH of the water does not change,and the water remains neutral.
B)The pH of the water decreases,and the water becomes more acidic.
C)The pH of the water decreases,and the water remains neutral.
D)The pH of the water increases,and the water becomes more acidic.
E)The pH of the water increases and the water remains neutral.

Question 7

Consider the following reactions:
a)Al³⁺ + 6H₂O Al(OH₂)₆³⁺
b)Al(OH₂)₆³⁺ Al(OH)(OH₂)₅²⁺ + H⁺
c)OCl^- + H₂O HOCl + OH^-
d)CN^- + H⁺ HCN
e)none of these
Which is associated with the definition of K_b?

A)a
B)b
C)c
D)d
E)e

Question 8

In which of the following reactions does the H₂PO₄^- ion act as an acid?

A)H₃PO₄ + H₂O $\to$ H₃O⁺ + H₂PO₄^-
B)H₂PO₄^- + H₂O $\to$ H₃O⁺ + HPO₄^2-
C)H₂PO₄^- + OH^- $\to$ H₃PO₄ + O^2-
D)The ion cannot act as an acid.
E)Two of these.

Question 9

What is the equilibrium constant for the following reaction? N₃^- + H₃O⁺ HN₃ + H₂O The K_a value for HN₃ = 1.9 $\times$ 10^-5.

A)5.3 $\times$ 10^-10
B)1.9 $\times$ 10^-9
C)1.9 $\times$ 10^-5
D)5.3 $\times$ 10⁴
E)1.9 $\times$ 10⁹

Question 10

Assuming that the value for K in the above reaction is greater than 1,this means that HF is a stronger acid than HOCl.

Question 11

The equilibrium constant for the reaction A^- + H⁺ HA is called:

A)K_a
B)K_b
C)
D)
E)K_wK_a

Question 12

Consider the reaction HOCl + F^- HF + OCl^-

-Given that K_a for HOCl is 3.5 $\times$ 10^-8 and the K_a for HF is 7.2 $\times$ 10^-4 (both at 25°C),which of the following is true concerning K for the above reaction at 25°C?

A)K is greater than 1.
B)K is less than 1.
C)K is equal to 1.
D)Cannot be determined with the above information.
E)None of these (A-D).

Question 13

The following three equations represent equilibria that lie far to the right.
HNO₃(aq)+ CN^-(aq) HCN(aq)+ NO₃^-(aq)
HCN(aq)+ OH^-(aq) H₂O(l)+ CN^-(aq)
H₂O(l)+ CH₃O^-(aq) CH₃OH(aq)+ OH^-(aq)
Identify the strongest base.

A)CH₃O^-
B)CH₃OH
C)CN^-
D)H₂O
E)NO₃^-

Question 14

Given the following acids and K_a values:

What is the order of increasing base strength?

A)CN^-,F^-,OAc^-,ClO₄^-
B)CN^-,OAc^-,F^-,ClO₄^-
C)CN^-,ClO₄^-,F^-,OAc^-
D)ClO₄^-,OAc^-,CN^-,F^-
E)ClO₄^-,F^-,OAc^-,CN^-

Question 15

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

A)HCl/OCl^-
B)H₂SO₄/SO₄^2-
C)NH₄⁺/NH₃
D)H₃O⁺/OH^-
E)more than one of these

Question 16

HA and HB are both weak acids in water,and HA is a stronger acid than HB.Which of the following statements is correct?

A)A^- is a stronger base than B^-,which is a stronger base than H₂O,which is a stronger base than Cl^-.
B)B^- is a stronger base than A^-,which is a stronger base than H₂O,which is a stronger base than Cl^-.
C)B^- is a stronger base than A^-,which is a stronger base than Cl^-,which is a stronger base than H₂O.
D)Cl^- is a stronger base than A^-,which is a stronger base than B^-,which is a stronger base than H₂O.
E)None of these (A-D)is correct.

Question 17

Consider the reaction HNO₂(aq)+ H₂O(l) H₃O⁺(aq)+ NO₂^-(aq).Which species is a conjugate base?

A)HNO₂(aq)
B)H₂O(l)
C)H₃O⁺(aq)
D)NO₂^-(aq)
E)two of these

Question 18

The hydrogen sulfate or bisulfate ion HSO₄^- can act as either an acid or a base in water solution.In which of the following equations does HSO₄^- act as an acid?

A)HSO₄^- + H₂O $\to$ H₂SO₄ + OH^-
B)HSO₄^- + H₃O⁺ $\to$ SO₃ + 2H₂O
C)HSO₄^- + OH^- $\to$ H₂SO₄ + O^2-
D)HSO₄^- + H₂O $\to$ SO₄^2- + H₃O⁺
E)none of these

Question 19

Which of the following is the equilibrium constant expression for the dissociation of the weak acid HOCl?

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

Question 20

The following three equations represent equilibria that lie far to the right.
HNO₃(aq)+ CN^-(aq) HCN(aq)+ NO₃^-(aq)
HCN(aq)+ OH^-(aq) H₂O(l)+ CN^-(aq)
H₂O(l)+ CH₃O^-(aq) CH₃OH(aq)+ OH^-(aq)
Identify the strongest acid.

A)HCN
B)HNO₃
C)H₂O
D)OH^-
E)CH₃OH

Question 21

For nitrous acid,HNO₂,K_a = 4.0 $\times$ 10^-4.Calculate the pH of 0.27 M HNO₂.

A)1.98
B)0.57
C)3.97
D)12.02
E)none of these

Question 22

A solution in which the pOH is 12.1 would be described as

A)very acidic
B)slightly acidic
C)neutral
D)very basic
E)slightly basic

Question 23

For weak acid,HX,K_a = 6.9 $\times$ 10^-6.Calculate the pH of a 0.13 M solution of HX.

A)0.89
B)3.02
C)6.05
D)10.98
E)none of these

Question 24

Calculate the pH of 0.203 M HNO₃(aq).

A)0.693
B)2.030
C)-1.140
D)13.797
E)1.595

Question 25

Which of the following indicates the most basic solution?

A)[H⁺] = 1 $\times$ 10^-10 M
B)pOH = 6.7
C)[OH^-] = 7 $\times$ 10^-5 M
D)pH = 4.2
E)At least two of the solutions are equally basic.

Question 26

Calculate the pH of a 0.031 M strong acid solution.

A)-1.51
B)1.51
C)12.49
D)15.51
E)none of these

Question 27

Calculate the [H⁺] in a solution that has a pH of 8.73.

A)1.9 $\times$ 10^-9 M
B)5.4 $\times$ 10^-6 M
C)8.7 $\times$ 10^-9 M
D)9.4 $\times$ 10^-1 M
E)7.2 $\times$ 10^-1 M

Question 28

What is the pOH of pure water at 65^oC? (K_w at 65^oC = 1.20 $\times$ 10^-13)

A)7.540
B)7.000
C)14.000
D)12.921
E)6.460

Question 29

You have 100.0 mL of a solution of hydrochloric acid that has a pH of 3.00.You add 100.0 mL of water to this solution.What is the resulting pH of the solution?

A)The pH = 5.00 (the average of 3.00 and 7.00).
B)The pH = 10.00 (3.00 + 7.00 = 10.00).
C)The pH = 3.00 (water is neutral and does not affect the pH).
D)None of the above is correct,but the pH must be greater than 3.00.
E)None of the above is correct,but the pH must be less than 3.00.

Question 30

The pK_a of HOCl is 7.5.Calculate the pH of a 0.31 M solution of HOCl.

A)7.50
B)6.50
C)4.00
D)10.00
E)0.31

Question 31

As water is heated,its pH decreases.This means that:

A)The water is no longer neutral.
B)The K_w value is decreasing.
C)The water has a lower [OH^-] than cooler water.
D)The dissociation of water is an endothermic process.
E)None of these.

Question 32

In deciding which of two acids is the stronger,one must know:

A)the concentration of each acid solution
B)the pH of each acid solution
C)the equilibrium constant of each acid
D)all of the above
E)both A and C must be known

Question 33

The pH of a solution at 25°C in which [OH^-] = 3.9 $\times$ 10^-5 M is:

A)4.41
B)3.90
C)9.59
D)4.80
E)none of these

Question 34

Calculate the [H⁺] in a solution that has a pH of 2.73.

A)2.7 M
B)11.3 M
C)1.9 $\times$ 10^-3 M
D)5.4 $\times$ 10^-12 M
E)none of these

Question 35

As water is heated,its pH decreases.This means that:

A)The water is no longer neutral.
B)[H⁺] > [OH^-]
C)[OH^-] > [H⁺]
D)A and B are correct.
E)None of these.

Question 36

Solid calcium hydroxide is dissolved in water until the pH of the solution is 11.44.The hydroxide ion concentration [OH^-] of the solution is:

A)3.6 $\times$ 10^-12 M
B)5.5 $\times$ 10^-3 M
C)2.8 $\times$ 10^-3 M
D)1.4 $\times$ 10^-3 M
E)none of these

Question 37

What volume of water must be added to 11.1 mL of a pH 2.0 solution of HNO₃ in order to change the pH to 4.0?

A)11.1 mL
B)89 mL
C)110 mL
D)1.10 $\times$ 10³ mL
E)28 mL

Question 38

Calculate the [H⁺] in a solution that has a pH of 9.88.

A)4.1 M
B)9.9 M
C)7.6 $\times$ 10^-5 M
D)1.3 $\times$ 10^-10 M
E)none of these

Question 39

Calculate the pOH of a 4.9 M solution of HCl.

A)-0.69
B)13.31
C)14.69
D)0.69
E)-0.96

Question 40

At 65°C,the ion-product constant of water,K_w,is 1.20 $\times$ 10^-13.The pH of pure water at 65°C is:

A)7.000
B)6.560
C)5.880
D)6.460
E)none of these

Question 41

A monoprotic weak acid when dissolved in water is 0.75% dissociated and produces a solution with a pH of 3.11.Calculate the K_a of the acid.

A)7.6 $\times$ 10^-3
B)1.0 $\times$ 10^-1
C)5.9 $\times$ 10^-6
D)Need to know the initial concentration of the acid.
E)None of these.

Question 42

How many moles of benzoic acid,a monoprotic acid with K_a = 6.4 $\times$ 10^-5,must be dissolved in 250.mL of H₂O to produce a solution with pH = 2.04?

A)1.3
B)0.00228
C)0.32
D)36
E)none of these

Question 43

In a solution prepared by dissolving 0.100 mole of propanoic acid in enough water to make 1.00 L of solution,the pH is observed to be 2.832.The K_a for propanoic acid (HC₃H₅O₂)is:

A)1.47 $\times$ 10^-3
B)2.20 $\times$ 10^-5
C)1.49 $\times$ 10^-2
D)4.55 $\times$ 10^-10
E)none of these

Question 44

Hypobromous acid,HOBr,has an acid dissociation constant of 2.5 $\times$ 10^-9 at 25°C.What is the pOH of a 0.075 M HOBr solution?

A)2.80
B)4.27
C)4.86
D)9.14
E)11.20

Question 45

A 8.5 $\times$ 10^-3 M solution of a weak acid is 4.6% dissociated at 25°C.In a 8.5 $\times$ 10^-4 M solution,the percentage of dissociation would be

A)the same
B)> 4.6%
C)< 4.6%
D)zero
E)need to know the K_a of the acid to answer this

Question 46

A solution of 8.01 M formic acid (HCOOH)is 0.47% ionized.What is the K_a value of formic acid?

A)3.8 $\times$ 10^-2
B)1.8 $\times$ 10^-4
C)4.7 $\times$ 10^-3
D)3.8
E)more data is needed

Question 47

Approximately how much water should be added to 10.0 mL of 11.1 M HCl so that it has the same pH as 0.90 M acetic acid (K_a = 1.8 $\times$ 10^-5)?

A)28 mL
B)276 mL
C)3 L
D)28 L
E)276 L

Question 48

Calculate the pOH of a 0.12 M solution of acetic acid (K_a = 1.8 $\times$ 10^-5).

A)2.83
B)8.33
C)5.67
D)11.17
E)1.91

Question 49

The pH of a 0.17 M solution of a weak monoprotic acid,HA,is 2.92.Calculate the K_a for this acid.

A)0.17
B)1.2 $\times$ 10^-3
C)7.1 $\times$ 10^-3
D)8.6 $\times$ 10^-6
E)7.3 $\times$ 10^-11

Question 50

Calculate the [H⁺] in a 0.068 M solution of HCN,K_a = 6.2 $\times$ 10^-10.

A)1.0 $\times$ 10^-7 M
B)6.5 $\times$ 10^-6 M
C)4.2 $\times$ 10^-11 M
D)1.3 $\times$ 10^-5 M
E)none of these

Question 51

Saccharin is a monoprotic acid.If the pH of a 4.41 $\times$ 10^-3 M solution of this acid is 2.53,what is the K_a of saccharin?

A)8.7 $\times$ 10^-6
B)2.0 $\times$ 10^-3
C)6.0 $\times$ 10^-3
D)2.9 $\times$ 10^-3
E)none of these

Question 52

A solution of 2.9 M weak acid is 0.52% ionized.What is the K_a value of this acid?

A)7.9 $\times$ 10^-5
B)1.5
C)1.5 $\times$ 10^-2
D)5.2 $\times$ 10^-3
E)none of these

Question 53

Determine the concentration of a solution of the weak acid HClO₂ (K_a = 1.10 $\times$ 10^-2)if it has a pH of 1.075.

A)0.644 M
B)0.0841 M
C)7.65 M
D)12.9 M
E)1.287 M

Question 54

Calculate the pH of a 0.13 M solution of HOCl,K_a = 3.5 $\times$ 10^-8.

A)4.17
B)8.34
C)9.83
D)1.00
E)3.76

Question 55

What concentration of acetic acid (K_a = 1.80 $\times$ 10^-5)has the same pH as that of 5.33 $\times$ 10^-3 M HCl?

A)17.2 M
B)12.4 M
C)1.58 M
D)5.33 $\times$ 10^-3 M
E)none of these

Question 56

When 2.5 $\times$ 10^-2 mol of nicotinic acid (a monoprotic acid)is dissolved in 350 mL of water,the pH is 3.05.Calculate the K_a of nicotinic acid.

A)1.3 $\times$ 10^-2
B)1.1 $\times$ 10^-5
C)7.1 $\times$ 10^-2
D)3.3 $\times$ 10^-5
E)none of these

Question 57

Calculate the pH of the following aqueous solution: 0.66 M HOCl (pK_a = 7.46)

A)10.18
B)3.82
C)7.64
D)6.36
E)none of these

Question 58

If an acid,HA,is 14.7% dissociated in a 1.0 M solution,what is the K_a for this acid?

A)1.7 $\times$ 10^-1
B)2.5 $\times$ 10^-2
C)1.5 $\times$ 10^-1
D)3.9 $\times$ 10¹
E)none of these

Question 59

Acetic acid, (HC₂H₃O₂)is a weak acid (K_a = 1.8 $\times$ 10^-5).Calculate the pH of a 15.1 M HC₂H₃O₂ solution.

A)-1.18
B)3.57
C)1.78
D)1.18
E)12.22

Question 60

The pH of a 0.118 M solution of an aqueous weak acid (HA)is 3.20.The K_a for the weak acid is:

A)5.4 $\times$ 10^-3
B)4.0 $\times$ 10^-7
C)3.4 $\times$ 10^-6
D)3.2
E)none of these

Question 61

Calculate the pH of a 0.51 M solution of KOH.

A)14.00
B)13.71
C)0.29
D)0.51
E)none of these

Question 62

Consider a solution made by mixing HCN (K_a = 6.2 $\times$ 10^-10)with HC₂H₃O₂ (K_a = 1.8 $\times$ 10^-5)in aqueous solution.What are the major species in solution?

A)H⁺,CN^-,H⁺,C₂H₃O₂^-,H₂O
B)HCN,H⁺,C₂H₃O₂^-,H₂O
C)H⁺,CN^-,HC₂H₃O₂,H₂O
D)H⁺,CN^-,H⁺,C₂H₃O₂^-,OH^-,H₂O
E)HCN,HC₂H₃O₂,H₂O

Question 63

Which of the following solutions contains the strongest acid?

A)5.00 M HCN (K_a = 6.2 $\times$ 10^-10)
B)3.50 M H₂C₆H₆O₆ (K_a1 = 7.9 $\times$ 10^-5,K_a2 = 1.6 $\times$ 10^-12).
C)2.50 M HC₂H₃O₂ (K_a = 1.8 $\times$ 10^-5)
D)4.00 M HOCl (K_a = 3.5 $\times$ 10^-8)
E)1.00 M HF (K_a = 7.2 $\times$ 10^-4)

Question 64

Calculate the pH of a 2.3 $\times$ 10^-3 M KOH solution.

A)2.64
B)12.36
C)11.36
D)1.64
E)10.36

Question 65

Calculate the pH of a 0.059 M solution of Ca(OH)₂.

A)13.07
B)12.77
C)0.93
D)1.23
E)none of these

Question 66

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

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

Question 67

The [OH^-] in a 0.87 M pyridine (C₅H₅N;K_b = 1.7 $\times$ 10^-9)solution is

A)1.5 $\times$ 10^-9 M
B)3.8 $\times$ 10^-5 M
C)0.87 M
D)4.4 $\times$ 10^-5 M
E)none of these

Question 68

The pain killer morphine is a weak base when added to water.The K_b is 1.6 $\times$ 10^-6.What is the pH of a 4.33 $\times$ 10^-3 M solution of morphine?

A)4.08
B)9.92
C)5.84
D)9.77
E)none of these

Question 69

Which of the following statements are true?

A)The pH of a strong acid is always lower than the pH of a weak acid.
B)The pH of a solution can never be negative.
C)For a conjugate acid-base pair,K_a = 1/K_b.
D)At least two of the statements A-C are true.
E)All of the statements A-C are false.

Question 70

Calculate the pOH of a 0.32 M solution of Ba(OH)₂.

A)0.49
B)0.19
C)13.81
D)13.51
E)none of these

Question 71

The following question refers to a solution that contains 1.99 M hydrofluoric acid,HF (K_a = 7.2 $\times$ 10^-4),and 3.00 M hydrocyanic acid,HCN (K_a = 6.2 $\times$ 10^-10). Determine the [CN^-] at equilibrium.

A)1.9 $\times$ 10^-9 M
B)3.8 $\times$ 10^-2 M
C)4.9 $\times$ 10^-8 M
D)6.2 $\times$ 10^-10 M
E)none of these

Question 72

Calculate the pH of a 0.02 M solution of KOH.

A)1.7
B)15.7
C)14.0
D)12.3
E)cannot calculate answer unless a volume is given

Question 73

The following question refers to a solution that contains 1.59 M hydrofluoric acid,HF (K_a = 7.2 $\times$ 10^-4),and 3.00 M hydrocyanic acid,HCN (K_a = 6.2 $\times$ 10^-10). What is the pH of this mixture of weak acids?

A)1.47
B)2.94
C)4.50
D)9.01
E)12.53

Question 74

Determine the percent dissociation of a 0.18 M solution of hypochlorous acid,HClO.The K_a for the acid is 3.5 $\times$ 10^-8.

A)3.5 $\times$ 10^-6 %
B)6.3 $\times$ 10^-9 %
C)7.9 $\times$ 10^-3 %
D)4.4 $\times$ 10^-2 %
E)1.1 $\times$ 10^-2 %

Question 75

Calculate the pH of a 2.28 M solution of NaOH.

A)0.358
B)13.642
C)14.358
D)2.28
E)none of these

Question 76

Calculate the percentage of pyridine (C₅H₅N)that forms pyridinium ion,C₅H₆N⁺,in a 0.72 M aqueous solution of pyridine (K_b = 1.7 $\times$ 10^-9).

A)1.7 $\times$ 10^-7 %
B)3.5 $\times$ 10^-3 %
C)2.4 $\times$ 10^-7 %
D)6.7 $\times$ 10^-3 %
E)4.9 $\times$ 10^-3 %

Question 77

Calculate the pH of a 5.7 M solution of aniline (C₆H₅NH₂;K_b = 3.8 $\times$ 10^-10):

A)4.33
B)9.67
C)5.34
D)8.66
E)none of these

Question 78

A 0.372-g sample of NaOH(s)is added to enough water to make 250.0 mL of solution.The pH of this solution is:

A)1.429
B)0.429
C)11.968
D)12.571
E)none of these

Question 79

Consider a 0.70 M solution of HOCl.If the molarity was decreased to 0.3 M,which of the following statements would be true?

A)The percent dissociation would not change.
B)The percent dissociation would increase.
C)The percent dissociation would decrease.
D)The equilibrium constant would stay the same.
E)Two of these.

Question 80

Calculate the pH of a 0.69 M solution of pyridine (C₅H₅N;K_b = 1.7 $\times$ 10^-9):

A)4.47
B)5.07
C)9.53
D)8.93
E)none of these