Deck 15: Aqueous Acidbase Equilibria

Question 1

Use the Brønsted-Lowry theory of acids and bases.

Answer 1

Water can act as an acid or a base. Any proton donor and the species generated by removing one of its protons are called a conjugate acid-base pair.
The water autohydrolysis equilibrium exists in any aqueous solution.
K_w [H₃O ]_eq[OH^-]_eq 1.0 X10⁻¹⁴ at 25°C in any aqueous solution.

Question 2

Relate pH to concentrations of ions in solution.

Answer 2

pH is a logarithmic scale. A change of 1 pH unit is a 10-fold change of [H₃O⁺(aq)].

Question 3

Calculate concentrations and pH in weak acid and base solutions.

Answer 3

In a solution of a weak acid, only a small fraction of the protons are transferred to the base. In a solution of a weak base, only a small fraction of the protons are transferred from the acid.

Question 4

Recognize and name some common acids and bases.

Question 5

Calculate the pH of solutions of salts of weak acids or bases.

Question 6

Explain the factors that contribute to the strength of an acid.

Question 7

Calculate concentrations in solutions involving multiple equilibria.

Question 8

A 45.0 mL sample of 0.15 M HCl is added to 38 mL of 0.2 M NaOH. What is the [H₃O⁺] of the resulting solution?

A) 8.5 x 10^-4 M
B) 0.010 M
C) 7.6 x 10^-3- M
D) 9.8 x 10^-13 M
E) 1.02 x 10^-14 M

Question 9

Identify the acids in the following reaction:H₂PO₄^- + H₂O ? H₃O⁺ + HPO₄²-

A) H₂PO₄^-
B) H₃O⁺
C) H₂PO₄^- and H₃O⁺
D) H₂O and H₃O⁺
E) H₂O and HPO₄^2-

Question 10

Identify the bases in the following reaction:H₂PO₄^- + OH^- ? H₂O + HPO₄^2-

A) H₂PO₄^-
B) OH^-
C) H₂PO₄^- and H₂O and H₃O⁺
D) OH^- and HPO₄^2-

Question 11

What is the pH of pure water at 99^oC, if K_w (99^oC) is 8.836 x 10^-13?

A) 7.00
B) -6.02
C) 6.02
D) 12.08
E) 13.88

Question 12

A 245.0 mL sample of 0.15 M Ba(OH)₂ is added to 438 mL of 0.2 M HNO₃. What is the pH of the resulting solution?

A) 0.021
B) 1.68
C) 12.32
D) 0.70
E) 13.30

Question 13

A 0.1 mL sample of 0.01 M HCl is added to 1000 L of water at 298ºK. What is the pH of the resulting solution?

A) 2.0
B) 5.0
C) 7.0
D) 10.0
E) 12.0

Question 14

A 0.001 mL sample of 0.01 M Ba(OH)₂ is added to 1000 L of water at 298ºK. What is the pH of the resulting solution?

A) 2.0
B) 5.0
C) 7.0
D) 10.0
E) 12.0

Question 15

To have solutions of HCl and acetic acid (CH₃CO₂H) with the same pH, which of the following needs to be done?

A) The concentration of each solution needs to be the same.
B) The concentration of HCl needs to be higher.
C) The concentration of acetic acid needs to be higher.
D) The solutions can never have the same pH.
E) Volume of acetic acid solution must be lower.

Question 16

A 1.35 g sample of ammonium chloride is added to sufficient water to give 150.0 mL of solution whose pH is less than 7.0. Several dissociation reactions occur. Which of the following goes essentially to completion?

A) H₂O $\rarr$ H⁺ + OH^-
B) NH₄⁺ $\rarr$ NH₃ + H⁺
C) NH₃ $\rarr$ NH₂^- + H⁺
D) NH₄Cl $\rarr$ NH₄⁺ + Cl^-
E) NH₃ + H₂O $\rarr$ OH^- + NH₄⁺

Question 17

A 1.35 g sample of ammonium chloride is added to sufficient water to give 150.0 mL of solution. Several reactions occur. Which of the following will determine the pH of the solution?

A) 2H₂O $\rightleftharpoons$ H₃O⁺ + OH^-
B) NH₄⁺ + H₂O $\rightleftharpoons$ NH₃ + H₃O⁺
C) NH₃ + H₂O $\rightleftharpoons$ NH₂^- + H₃O⁺
D) NH₄Cl $\rarr$ NH₄⁺ + Cl^-
E) NH₃ + H₂O $\rarr$ OH^- + NH₄⁺

Question 18

Identify the major species present in a 0.15 M solution of sodium monohydrogen phosphate, Na₂HPO₄.

A) Na⁺, PO₄^3-, H⁺, H₂O
B) Na₂HPO₄, H₂O
C) Na⁺, H₂PO₄^-, OH^-, H₂O
D) Na⁺, HPO₄^2-, H₂O
E) Na₂HPO₄, Na⁺, HPO₄^2-, H₂O

Question 19

Which of the following is a weak base?

A) CH₃OH
B) KOH
C) CH₃CO₂H
D) NH₄Cl
E) CH₃CH₂CH₂CO₂^-

Question 20

Which of the following is a weak acid?

A) CH₃OH
B) NaOH
C) CH₃CO₂^-
D) NH₄Cl
E) CH₃CH₂CH₂CO₂CH₃

Question 21

Which of the following is a weak base?

A) NaOH
B) CH₃CO₂H
C) (CH₃)₂NH
D) KOH
E) HClO₂

Question 22

Which of the following is the conjugate base of the dihydrogenphosphate ion, H₂PO₄^-?

A) H₃PO₄
B) NaH₂PO₄
C) OH^-
D) HPO₄^2-
E) PO₄^3-

Question 23

Which is the conjugate acid of HAsO₄^2-?

A) H₃AsO₄
B) H₃O⁺
C) OH^-
D) H₂AsO₄^2-
E) AsO₄^3-

Question 24

The K_as for HClO₂, HClO, HIO and HIO₃ are 1.1x10^-2, 4.0x10^-8, 3.2x10^-11, and 1.7x10^-1, respectively. Which of the following is the strongest base?

A) ClO₂^-
B) ClO^-
C) IO^-
D) IO₃^-

Question 25

A solution of total volume 0.50 L was prepared by the addition of 0.10 moles of KF to sufficient water. From the following, select the major species and the pH of the solution.

A) K⁺, HF; H O^-, H₂O, pH = 8.23
B) K⁺, F^-; H⁺, H₂O, pH = 5.76
C) K⁺, H₂O, F^-, pH = 8.23
D) K⁺, H₂O, F^-, pH = 5.76
E) KF, H₃O⁺, 6.27

Question 26

Although you may NOT think of these compounds as being acids, your organic chemistry instructor probably will. Consider the H atoms in bold print in the following compounds.
A= CH₃CH₂(C=O)CH₃
B = CH₃CH₂(C=O)CH₃
C= CH₃CH₂CH₂(C=O)CH₃
D= CH₃CH₂(C=O)CH₂(C=O)CH₃Select the sequence where the bold H atoms are in order of increasing acidity.

A) D, B, A
B) A, B, D
C) C, B, A
D) A, C, D
E) D, A, C

Question 27

Which of the following salt solutions will be the most basic?

A) 0.5 M NaNO₃
B) 0.5 M NaNO₂
C) 0.75 M NaClO₂
D) 0.75 M NaClO₄
E) 0.5 M NH₄Cl

Question 28

In the reaction between methyl amine, H₂N(CH₃) and acetic acid, CH₃CO₂H, the conjugate acid and base produced are

A) H⁺ and OH^-.
B) H₂N(CH₃) and CH₃CO₂H.
C) H₃N(CH₃)⁺ and CH₃CO₂^-.
D) H₃N(CH₃)⁺ and OH^-.
E) H⁺ and CH₃CO₂^-.

Question 29

When 0.10 moles of HCl are added to 1 L of solution containing 0.12 moles of aqueous Na₂CO₃, the major species present are

A) Na⁺, Cl^-, H₂O, HCO₃^-.
B) Na⁺, Cl^-, H₂O, CO₃^2-.
C) Na⁺, Cl^-, H₂O, HCO₃^-, CO₃^2- .
D) HCl, Na⁺, CO₃^2-.
E) Na⁺, Cl^-, H₂O, H₂CO₃, CO₃².

Question 30

Solid NaClO is added to water. What are the major species present?

A) NaClO, HClO and water
B) Na⁺, Cl^-, O₂ and water
C) Na⁺, Cl₂, O^2- and water
D) Na⁺, ClO^- and water
E) NaClO, Na⁺, ClO^-, water

Question 31

What is the pH of a 0.01 M solution of sulphuric acid?

A) 2
B) 1.70
C) 1.85
D) 1.46
E) 12

Question 32

Using the following table, which aqueous 1.0 M solution will have the lowest pH?

A) Na₂CO₃
B) NaHS
C) NaC₂H₃O₂
D) NaBr
E) Na₃PO₄

Question 33

What are the hydronium and hydroxide ion concentrations in a solution of 9.0 M HCl?

Question 34

If 250 ml of 9.0 M HCl is diluted with 75 ml of water, what is the hydroxide ion concentration of the resulting solution?

Question 35

What are the hydronium and hydroxide ion concentrations in a solution of 1.00 x10^-5 M Ca(OH)₂?

Question 36

What are the hydronium and hydroxide ion concentrations in a solution of 6.4 M NaOH?

Question 37

At 99°C, the hydronium concentration of pure water is 9.4 x 10^-7. Is the solution neutral, acidic, or basic?

Question 38

A 245.0 mL sample of 0.15 M Ba(OH)₂ is added to 438 mL of 0.2 M HNO₃. What is the[OH^-] of the resulting solution?

Question 39

What is the pH of an 800 mL solution prepared from 25 g of KOH and water?

Question 40

What is the pH of a 9 M HCl solution?

Question 41

What is the pH of a 9 M NaOH solution?

Question 42

What is the pH of a solution that is 1 x10^-10 M in HNO₃?

Question 43

What is the pOH of a solution of 1.00 x10^-5 M Ca(OH)₂?

Question 44

What is the [OH^-] of a solution whose pH is 7.41?

Question 45

What is the [H₃O⁺] of a solution whose pOH is 9.45?

Question 46

What is the [H₃O⁺] of blood whose measured pH = 7.46?

Question 47

A solution is made by adding 0.1000 mole of the weak acid, HF, to water, and then adding water until the volume of the solution is 1.000 L. Of the acid added, 8.5% is dissociated.
a) What is K_a?
b) What is the pH of the solution?

Question 48

Hydroxyl amine, HONH₂, is a weak base with K_b of 8.7x10^-9. What to extent is a 1.25 molar solution ionized?

Question 49

Draw a molecular picture that illustrates the reaction that makes solutions of methylamine (CH₃NH₂) basic.

Question 50

Draw a molecular picture of the reaction that makes solutions of formic acid acidic.

Question 51

What is the pH of a 0.600 M HNO₂ solution (K_a=5.6 x10^-4)?

Question 52

What is the pH of a 0.0250M CH₃NH₂ solution (K_b = 4.35 x10^-4)?

Question 53

Determine the % ionized of a 0.200 M solution of lactic acid (pK_a = 3.85).

Question 54

Determine the K_a of a 0.200 M solution of lactic acid that has a pH = 2.27.

Question 55

Consider the reaction of monohydrogen carbonate with nitrous acid, HNO₂. Write the equation of reaction and identify each conjugate pair of acids and bases.

Question 56

Consider the reaction of monohydrogen carbonate with ammonia. Write the equation of reaction and identify each conjugate pair of acids and bases.

Question 57

The conjugate acid of HS^-1 is ______ and the conjugate base of H₂O is ______.

Question 58

What is the name for the following acids or bases?

Question 59

Sodium formate is added to distilled water. Will the resulting solution be acidic, basic or neutral?

Question 60

Draw a molecular picture that illustrates the reaction responsible for the alkaline nature of sodium phosphate solutions.

Question 61

Draw a molecular picture that illustrates the reaction responsible for the acidity of solutions of the dimethylammonium ion, (CH₃)₂NH₂⁺.

Question 62

If the K_b of IO^-(aq) is 3.1x10^-4 what is the K_a for hypoiodous acid, HIO?

Question 63

Solid pyridinium chloride, C₅H₅NHCl,(5 g) is added to 200 ml of water. What are the major species in solution?

Question 64

What is the pH of a solution that is prepared by the addition of 15.0 g of NaF to sufficient water to make 1.2 L of solution? (K_a = 6.3 x10^-4, pK_a = 3.20)

Question 65

What is the pH of a 0.15 M solution of NaNO₃?

Question 66

What is the pH of a solution of 20.0 g of NaIO₃ in sufficient water to make 988 ml of solution: K_a (Iodic acid, HIO₃ = 1.7x10^-1)?

Question 67

Describe what would happen to the pH of a HNO₂ solution if some KNO₂ was added and explain why.

Question 68

Which is the strongest acid, HClO₄, H ClO₃, H ClO₂, H ClO and why?

Question 69

Which is the strongest base, H₂PO₄^-, HPO₄^2- or PO₄^3- and why?

Question 70

Which acid is a strong acid, HClO₄ or HBrO₄ and why?

Question 71

The pK_as of the acids, HXO (X= I, Cl, Br) are (in random order) 8.69, 7.53 10.64. Which is the value for HIO?

Question 72

Which of the group 16 binary hydrides would you expect to be the strongest acid?

Question 73

Which is a stronger acid, Cl₃CCO₂H or CH₃CO₂H and why?

Question 74

The pK_as for the carboxylic acids (CH₃CH₂CO₂H, CH₃CO₂H, and HCO₂H) are (in random order) 3.75, 4.75, 4.87. Place the appropriate pK_a with its acid.

Question 75

Use the following table to answer the questions

-Write the equilibrium reaction for K_b2 of H₃PO₄.

Question 76

Use the following table to answer the questions

-Write the equilibrium reaction for K_b2 of H₂CO₃.

Question 77

Use the following table to answer the questions

-A solution is made by dissolving 0.1 mole Na₃PO₄ in water, adding HCl and water to give 1.00 L of solution with a pH of 7.60. What is the [HPO₄^-] in this solution?

Question 78

Use the following table to answer the questions

-A solution is made by dissolving 0.1 mole Na₂HPO₄ in 1.00 L water. What is the [H₂PO₄^-] in this solution?

Question 79

Use the following table to answer the questions


-What will be the dominant phosphate species in a solution when a small amount of H₃PO₄ is added to a solution whose pH is maintained at pH = 11?