Deck 17: Acid-Base Equilibria and Solubility Equilibria

Question 1

A solution is prepared by mixing 500. mL of 0.10 M NaOCl and 500. mL of 0.20 M HOCl. What is the pH of this solution? [K_a(HOCl)= 3.2 * 10^-8]

A)4.10
B)7.00
C)7.19
D)7.49
E)7.80

Answer 1

7.19

Question 2

Assuming equal concentrations of conjugate base and acid, which one of the following mixtures is suitable for making a buffer solution with an optimum pH of 4.6-4.8?

A)CH₃COO₂Na / CH₃COOH (K_a = 1.8 * 10^-5)
B)NH₃ / NH₄Cl (K_a = 5.6 * 10^-10)
C)NaOCl / HOCl (K_a = 3.2 * 10^-8)
D)NaNO₂ / HNO₂ (K_a = 4.5 * 10^-4)
E)NaCl / HCl

Answer 2

CH₃COO₂Na / CH₃COOH (K_a = 1.8 * 10^-5)

Question 3

Calculate the percent ionization of cyanic acid, K_a = 2.0 * 10^-4, in a buffer solution that is 0.50 M HCNO and 0.10 M NaCNO.

A)0.02%
B)0.10%
C)0.20%
D)2.0%
E)20%

Answer 3

0.20%

Question 4

You have 500.0 mL of a buffer solution containing 0.30 M acetic acid (CH₃COOH)and 0.20 M sodium acetate (CH₃COONa). What will the pH of this solution be after the addition of 20.0 mL of 1.00 M NaOH solution? [K_a = 1.8 * 10^-5]

A)4.65
B)4.71
C)4.56
D)4.84
E)5.07

Question 5

You are asked to go into the lab and prepare an acetic acid - sodium acetate buffer solution with a pH of 4.00 ± 0.02. What molar ratio of CH₃COOH to CH₃COONa should be used?

A)0.18
B)0.84
C)1.19
D)5.50
E)0.10

Question 6

A titration of an acid and base to the equivalence point results in a noticeably acidic solution. It is likely this titration involves

A)a strong acid and a weak base.
B)a weak acid and a strong base.
C)a weak acid and a weak base (where K_a equals K_b).
D)a strong acid and a strong base.

Question 7

Calculate the pH of a buffer solution prepared by dissolving 0.20 mole of cyanic acid (HCNO)and 0.80 mole of sodium cyanate (NaCNO)in enough water to make 1.0 liter of solution. [K_a(HCNO)= 2.0 * 10^-4]

A)0.97
B)3.10
C)4.40
D)3.70
E)4.30

Question 8

Calculate the pH of a buffer solution that contains 0.25 M benzoic acid (C₆H₅CO₂H)and 0.15M sodium benzoate (C₆H₅COONa). [K_a = 6.5 * 10^-5 for benzoic acid]

A)3.97
B)4.83
C)4.19
D)3.40
E)4.41

Question 9

Assuming equal concentrations of conjugate base and acid, which one of the following mixtures is suitable for making a buffer solution with an optimum pH of 9.2-9.3?

A)CH₃COONa / CH₃COOH (K_a = 1.8 * 10^-5)
B)NH₃ / NH₄Cl (K_a = 5.6 * 10^-10)
C)NaOCl / HOCl (K_a = 3.2 * 10^-8)
D)NaNO₂ / HNO₂ (K_a = 4.5 * 10^-4)
E)NaCl / HCl

Question 10

Calculate the pH of a buffer solution prepared by dissolving 0.20 mole of sodium cyanate (NaCNO)and 1.0 mole of cyanic acid (HCNO)in enough water to make 1.0 liter of solution. [K_a(HCNO)= 2.0 * 10^-4]

A)0
B)3.0
C)3.7
D)4.4
E)5.0

Question 11

What is the net ionic equation for the reaction that occurs when small amounts of hydrochloric acid are added to a HOCl/NaOCl buffer solution?

A)H⁺ + H₂O $\rarr$ H₃O⁺
B)H⁺ + OCl^- $\rarr$ HOCl
C)HOCl $\rarr$ H⁺ + OCl^-
D)H⁺ + HOCl $\rarr$ H₂OCl⁺
E)HCl + HOCl $\rarr$ H₂O + Cl₂

Question 12

Over what range of pH is a HOCl - NaOCl buffer effective?

A)pH 2.0 - pH 4.0
B)pH 7.5 - pH 9.5
C)pH 6.5 - pH 8.5
D)pH 6.5 - pH 9.5
E)pH 1.0 - pH 14.0

Question 13

You have 500.0 mL of a buffer solution containing 0.20 M acetic acid (CH₃COOH)and 0.30 M sodium acetate (CH₃COONa). What will the pH of this solution be after the addition of 20.0 mL of 1.00 M NaOH solution? [K_a = 1.8 * 10^-5]

A)4.41
B)4.74
C)4.56
D)4.92
E)5.07

Question 14

Which one of the following combinations cannot function as a buffer solution?

A)HCN and KCN
B)NH₃ and (NH₄)₂SO₄
C)HNO₃ and NaNO₃
D)HF and NaF
E)HNO₂ and NaNO₂

Question 15

Which one of the following is a buffer solution?

A)0.40 M HCN and 0.10 KCN
B)0.20 M CH₃COOH
C)1.0 M HNO₃ and 1.0 M NaNO₃
D)0.10 M KCN
E)0.50 M HCl and 0.10 NaCl

Question 16

Calculate the pH of a solution that is 0.410 M in HOCl and 0.050 M in NaOCl. [K_a(HOCl)= 3.2 * 10^-8]

A)0.39
B)3.94
C)6.58
D)7.49
E)8.40

Question 17

Acid dissociation constants for phosphoric acid are given below. A buffer with a pH = 7.4 can best be made by using

A)H₃PO₄ and NaH₂PO₄.
B)NaH₂PO₄ and Na₂HPO₄.
C)Na₂HPO₄ and Na₃PO₄.
D)only NaH₂PO₄.
E)only Na₂HPO₄.

Question 18

Consider a buffer solution prepared from HOCl and NaOCl. Which is the net ionic equation for the reaction that occurs when NaOH is added to this buffer?

A)OH^- + HOCl $\rarr$ H₂O + OCl^-
B)OH^- + OCl^- $\rarr$ HOCl + O^2-
C)Na⁺ + HOCl $\rarr$ NaCl + OH^-
D)H⁺ + HOCl $\rarr$ H₂ + OCl^-
E)NaOH + HOCl $\rarr$ H₂O + NaCl

Question 19

The pH at the equivalence point of a titration may differ from 7.0 due to

A)the initial concentration of the standard solution.
B)the indicator used.
C)the self-ionization of H₂O.
D)the initial pH of the unknown.
E)hydrolysis of the salt formed.

Question 20

For which type of titration will the pH be basic at the equivalence point?

A)Strong acid vs. strong base.
B)Strong acid vs. weak base.
C)Weak acid vs. strong base.
D)All of the above.
E)None of the above.

Question 21

The solubility product for chromium(III)fluoride is K_sp = 6.6 * 10^-11. What is the molar solubility of chromium(III)fluoride?

A)1.6 * 10^-3 M
B)1.2 * 10^-3 M
C)6.6 * 10^-11 M
D)2.2 * 10^-3 M
E)1.6 * 10^-6 M

Question 22

The K_sp value for lead(II)chloride is 2.4 * 10^-4. What is the molar solubility of lead(II)chloride?

A)2.4 * 10^-4 mol/L
B)6.2 * 10^-2 mol/L
C)7.7 * 10^-3 mol/L
D)3.9 * 10^-2 mol/L
E)6.0 * 10^-5 mol/L

Question 23

Calculate the pH at the equivalence point for the titration of 0.20 M HCl with 0.20 M NH₃ (K_b = 1.8 * 10^-5).

A)2.87
B)4.98
C)5.12
D)7.00
E)11.12

Question 24

What mass of sodium fluoride must be added to 250. mL of a 0.100 M HF solution to give a buffer solution having a pH of 3.50? [K_a(HF)= 7.1 * 10^-4]

A)0.49 g
B)1.5 g
C)3.4 g
D)2.3 g
E)0.75 g

Question 25

The K_sp for silver(I)phosphate is 1.8 * 10^-18. Calculate the molar solubility of silver(I)phosphate.

A)1.6 * 10^-5 M
B)2.1 * 10^-5 M
C)3.7 * 10^-5 M
D)7.2 * 10^-1 M
E)1.8 * 10^-1 M

Question 26

The molar solubility of manganese(II)carbonate is 4.2 * 10^-6 M. What is K_sp for this compound?

A)4.2 * 10^-6
B)8.4 * 10^-6
C)3.0 * 10^-16
D)1.8 * 10^-11
E)2.0 * 10^-3

Question 27

The solubility of strontium carbonate is 0.0011 g/100 mL at 20^oC. Calculate the K_sp value for this compound.

A)7.5 * 10^-5
B)1.5 * 10^-4
C)5.6 * 10^-9
D)7.5 * 10^-6
E)1.5 * 10^-3

Question 28

What is the pH at the equivalence point in the titration of 100 mL of 0.10 M HCl with 0.10 M NaOH?

A)1.0
B)6.0
C)7.0
D)8.0
E)13.0

Question 29

For PbCl₂ (K_sp = 2.4 * 10^-4), will a precipitate of PbCl₂ form when 0.10 L of 3.0 * 10^-2 M Pb(NO₃)₂ is added to 400 mL of 9.0 * 10^-2 M NaCl?

A)Yes, because Q > K_sp.
B)No, because Q < K_sp.
C)No, because Q = K_sp.
D)Yes, because Q < K_sp.

Question 30

The solubility of lead(II)iodide is 0.064 g/100 mL at 20^oC. What is the solubility product for lead(II)iodide?

A)1.1 * 10^-8
B)3.9 * 10^-6
C)1.1 * 10^-11
D)2.7 * 10^-12
E)1.4 * 10^-3

Question 31

What mass of ammonium nitrate must be added to 350. mL of a 0.150 M solution of ammonia to give a buffer having a pH of 9.00? (K_b(NH₃)= 1.8 * 10^-5)

A)7.6 g
B)2.4 g
C)5.4 g
D)11 g
E)3.3 g

Question 32

The solubility product for barium sulfate is 1.1 * 10^-10. Calculate the molar solubility of barium sulfate.

A)5.5 * 10^-11 mol/L
B)1.1 * 10^-5 mol/L
C)2.1 * 10^-5 mol/L
D)1.1 * 10^-10 mol/L
E)2.2 * 10^-10 mol/L

Question 33

The solubility product for calcium phosphate is K_sp = 1.3 * 10^-26. What is the molar solubility of calcium phosphate?

A)1.3 * 10^-26 M
B)1.5 * 10^-7 M
C)2.6 * 10^-6 M
D)4.6 * 10^-6 M
E)6.6 * 10^-6 M

Question 34

Calculate the silver ion concentration in a saturated solution of silver(I)carbonate (K_sp = 8.1 * 10^-12).

A)5.0 * 10^-5 M
B)2.5 * 10^-4 M
C)1.3 * 10^-4 M
D)2.0 * 10^-4 M
E)8.1 * 10^-4 M

Question 35

The molar solubility of magnesium carbonate is 1.8 * 10^-4 mol/L. What is K_sp for this compound?

A)1.8 * 10^-4
B)3.6 * 10^-4
C)1.3 * 10^-7
D)3.2 * 10^-8
E)2.8 * 10^-14

Question 36

Methyl red is a common acid-base indicator. It has a K_a equal to 6.3 * 10^-6. Its un-ionized form is red and its anionic form is yellow. What color would a methyl red solution have at pH = 7.8?

A)green
B)red
C)blue
D)yellow
E)violet

Question 37

The molar solubility of lead(II)iodate in water is 4.0 * 10^-5 mol/L. Calculate K_sp for lead(II)iodate.

A)1.6 * 10^-9
B)6.4 * 10^-14
C)2.6 * 10^-13
D)4.0 * 10^-5
E)4.0 * 10^-15

Question 38

What is the pH at the equivalence point in the titration of 100 mL of 0.10 M HCN (K_a = 4.9 * 10^-10)with 0.10 M NaOH?

A)3.0
B)6.0
C)7.0
D)11.0
E)12.0

Question 39

Calculate the pH of the solution resulting from the addition of 10.0 mL of 0.10 M NaOH to 50.0 mL of 0.10 M HCN (K_a = 4.9 * 10^-10)solution.

A)5.15
B)8.71
C)5.85
D)9.91
E)13.0

Question 40

The molar solubility of tin(II)iodide is 1.28 * 10^-2 mol/L. What is K_sp for this compound?

A)8.4 * 10^-6
B)1.28 * 10^-2
C)4.2 * 10^-6
D)1.6 * 10^-4
E)2.1 * 10^-6

Question 41

Find the concentration of calcium ions in a solution made by adding 3.50 g of calcium fluoride to 750. mL of 0.125 M NaF. [For CaF₂, K_sp = 3.95 * 10^-11.]

A)3.16 * 10^-10 M
B)2.53 * 10^-9 M
C)4.29 * 10^-4 M
D)6.32 * 10^-10 M
E)2.15 * 10^-4 M

Question 42

Calculate the concentration of chloride ions in a saturated lead(II)chloride (K_sp = 2.4 * 10^-4)solution.

A)2.4 * 10^-4 M
B)4.8 * 10^-4 M
C)3.9 * 10^-2 M
D)1.2 * 10^-1 M
E)7.8 * 10^-2 M

Question 43

A saturated sodium carbonate solution at 100°C contains 45.5 g of dissolved sodium carbonate per 100. mL of solution. The solubility product constant for sodium carbonate at this temperature is

A)79.0.
B)0.316.
C)0.0790.
D)36.8.
E)316.

Question 44

Will a precipitate of magnesium fluoride form when 200. mL of 1.9 * 10^-3 M MgCl₂ are added to 300. mL of 1.4 * 10^-2 M NaF? [K_sp (MgF₂)= 6.9 * 10^-9]

A)Yes, Q > K_sp
B)No, Q < K_sp
C)No, Q = K_sp
D)Yes, Q < K_sp

Question 45

Will a precipitate (ppt)form when 300. mL of 5.0 * 10^-5 M AgNO₃ are added to 200. mL of 2.5 * 10^-7 M NaBr? Answer yes or no, and identify the precipitate if there is one.

A)Yes, the ppt is AgNO₃(s).
B)Yes, the ppt is AgBr(s).
C)Yes, the ppt is NaBr(s).
D)Yes, the ppt is NaNO₃(s).
E)No, a precipitate will not form.

Question 46

Calculate the silver ion concentration in a saturated solution of silver(I)sulfate (K_sp = 1.4 * 10^-5).

A)1.5 * 10^-2 M
B)2.4 * 10^-2 M
C)3.0 * 10^-2 M
D)1.4 * 10^-5 M
E)None of the above.

Question 47

Will a precipitate (ppt)form when 300. mL of 2.0 * 10^-5 M AgNO₃ are added to 200. mL of 2.5 * 10^-9 M NaI? Answer yes or no, and identify the precipitate if there is one.

A)Yes, the ppt is AgNO₃(s).
B)Yes, the ppt is NaNO₃(s).
C)Yes, the ppt is NaI(s).
D)Yes, the ppt is AgI(s).
E)No, a precipitate will not form.

Question 48

Which of the following would decrease the K_sp for PbI₂?

A)Lowering the pH of the solution
B)Adding a solution of Pb(NO₃)₂
C)Adding a solution of KI
D)None of the above-the K_sp of a compound is constant at constant temperature.

Question 49

Find the concentration of Pb²⁺ ions in a solution made by adding 5.00 g of lead(II)iodide to 500. mL of 0.150 M KI. [For PbI₂, K_sp = 1.39 * 10^-8.]

A)3.04 * 10^-4 M
B)1.54 * 10^-7 M
C)6.18 * 10^-7 M
D)1.52 * 10^-4 M
E)9.27 * 10^-8 M

Question 50

Which response has both answers correct? Will a precipitate form when 250 mL of 0.33 M Na₂CrO₄ are added to 250 mL of 0.12 M AgNO₃? [K_sp(Ag₂CrO₄)= 1.1 * 10^-12] What is the concentration of the silver ion remaining in solution?

A)Yes, [Ag⁺] = 2.9 * 10^-6 M.
B)Yes, [Ag⁺] = 0.060 M.
C)Yes, [Ag⁺] = 1.3 * 10^-4 M.
D)No, [Ag⁺] = 0.060 M.
E)No, [Ag⁺] = 0.105 M.

Question 51

Calculate the minimum concentration of Cr³⁺ that must be added to 0.095 M NaF in order to initiate a precipitate of chromium(III)fluoride. (For CrF₃ , K_sp = 6.6 * 10^-11.)

A)0.023 M
B)0.032 M
C)7.7 * 10^-8 M
D)2.9 * 10^-9 M
E)6.9 * 10^-10 M

Question 52

Will a precipitate of magnesium fluoride form when 300. mL of 1.1 * 10^-3 M MgCl₂ are added to 500. mL of 1.2 * 10^-3 M NaF? [K_sp (MgF₂)= 6.9 * 10^-9]

A)Yes, Q > K_sp
B)No, Q < K_sp
C)No, Q = K_sp
D)Yes, Q < K_sp

Question 53

Calculate the concentration of fluoride ions in a saturated barium fluoride (K_sp = 1.7 * 10^-6)solution.

A)7.6 * 10^-3 M
B)1.5 * 10^-2 M
C)3.4 * 10^-5 M
D)1.7 * 10^-6 M
E)3.4 * 10^-6 M

Question 54

To 1.00 L of a 0.100 M aqueous solution of benzoic acid (C₆H₅COOH)is added 1.00 mL of 12.0 M HCl. What is the percentage ionization of the benzoic acid in the resulting solution? [K_a(C₆H₅COOH)= 6.5 * 10^-5]

A)3.3%
B)12%
C)1.3%
D)0.52%
E)0.065%

Question 55

Calculate the minimum concentration of Mg²⁺ that must be added to 0.10 M NaF in order to initiate a precipitate of magnesium fluoride. (For MgF₂ , K_sp = 6.9 * 10^-9.)

A)1.4 * 10⁷ M
B)6.9 * 10^-9 M
C)6.9 * 10^-8 M
D)1.7 * 10^-7 M
E)6.9 * 10^-7 M

Question 56

Will a precipitate (ppt)form when 20.0 mL of 1.1 * 10^-3 M Ba(NO₃)₂ are added to 80.0 mL of 8.4 * 10^-4 M Na₂CO₃?

A)Yes, the ppt is Ba(NO₃)₂.
B)Yes, the ppt is NaNO₃.
C)Yes, the ppt is BaCO₃.
D)Yes, the ppt is Na₂CO₃.
E)No, a precipitate will not form.

Question 57

The K_sp for silver(I)phosphate is 1.8 * 10^-18. Determine the silver ion concentration in a saturated solution of silver(I)phosphate.

A)1.6 * 10^-5 M
B)2.1 * 10^-5 M
C)3.7 * 10^-5 M
D)1.1 * 10^-13 M
E)4.8 * 10^-5 M

Question 58

Will a precipitate form (yes or no)when 50.0 mL of 1.2 * 10^-3 M Pb(NO₃)₂ are added to 50.0 mL of 2.0 * 10^-4 M Na₂S? If so, identify the precipitate.

A)Yes, the precipitate is PbS.
B)Yes, the precipitate is NaNO₃.
C)Yes, the precipitate is Na₂S.
D)Yes, the precipitate is Pb(NO₃)₂.
E)No, a precipitate will not form.

Question 59

To 1.00 L of a 0.100 M aqueous solution of the week base pyridine (C₅H₅N)is added 1.00 mL of 14.0 M NaOH. What fraction of the pyridine molecules in the resulting solution react with water to release hydroxide ions? [K_b(C₅H₅N)= 1.7 * 10^-9]

A)1.2 * 10^-7
B)4.1 * 10^-5
C)0.14
D)2.4 * 10^-10
E)1.3 * 10^-5

Question 60

A saturated sodium carbonate solution at 0°C contains 7.1 g of dissolved sodium carbonate per 100. mL of solution. The solubility product constant for sodium carbonate at this temperature is

A)1.2.
B)0.30.
C)3.0 * 10^-4.
D)0.90.
E)1.2 * 10^-3.

Question 61

What volume of 0.200 M potassium hydroxide should be added to 300. mL of 0.150 M propanoic acid (C₂H₅COOH)to obtain a solution with a pH of 5.25? [K_a(C₂H₅COOH)= 1.34 * 10^-5]

A)32 mL
B)210 mL
C)160 mL
D)65 mL
E)13 mL

Question 62

The K_sp of CaF₂ is 4 * 10^-11. What is the maximum concentration of Ca²⁺ possible in a 0.10 M NaF solution?

Question 63

Write an equation showing the net reaction that occurs when a strong acid is added to a CO₃^2-/HCO₃^- buffer solution (for carbonic acid, K_a1 = 4.2 * 10^-7, K_a2 = 2.4 * 10^-8):

Question 64

Write a net ionic equation for the reaction occurring when a small amount of sodium hydroxide is added to a NaNO₂/HNO₂ buffer.

Question 65

What is the optimum pH of a sodium formate/formic acid buffer? (For formic acid, K_a = 1.7 * 10^-4)

Question 66

What is the effective pH range for a sodium acetate/acetic acid buffer? (For CH₃COOH, K_a= 1.8 * 10^-5)

Question 67

Bromothymol blue is a common acid-base indicator. It has a K_a equal to 1.6 * 10^-7. Its un-ionized form is yellow and its conjugate base is blue. What color would a solution have at pH = 5.8?

Question 68

Write an equation showing the net reaction that occurs when a strong base is added to a CO₃^2-/HCO₃^- buffer solution (for carbonic acid, K_a1 = 4.2 * 10^-7, K_a2 = 2.4 * 10^-8):

Question 69

Will a precipitate of AgCl form when 0.050 mol NaCl(s)and 0.050 mol AgNO₃(s)are dissolved in 500. mL of 3.0 M NH₃? [K_f for Ag(NH₃)₂⁺ is 1.5 * 10⁷; K_sp(AgCl)= 1.6 * 10^-10]

Question 70

Calculate the pH at the equivalence point for the titration of 0.25 M CH₃COOH with 0.25 M NaOH. (For CH₃COOH, K_a= 1.8 * 10^-5)

Question 71

Write a net ionic equation for the reaction that occurs when a small amount of hydrochloric acid is added to a buffer solution containing NH₄Cl and NH₃.

Question 72

Calculate the equilibrium constant K_c for the following overall reaction:
AgCl(s)+ 2CN^-(aq) $\rarr$ Ag(CN)₂^-(aq)+ Cl^-(aq)
For AgCl, K_sp = 1.6 * 10^-10; for Ag(CN)₂^-, K_f = 1.0 * 10²¹.

Question 73

What molar ratio of benzoate ion to benzoic acid would be required to prepare a buffer with a pH of 5.20? [K_a(C₆H₅COOH)= 6.5 * 10^-5]

Question 74

Describe how to make a sodium formate (HCOONa)/formic acid (HCOOH)buffer that has a pH of 4.77.

Question 75

Calculate the pH at the equivalence point for the titration of 0.22 M HCN with 0.22 M NaOH. (K_a = 4.9 * 10^-10 for HCN)

Question 76

Calculate the pH of a solution that is 0.15 M CH₃COOH and 0.75 M CH₃COONa.

Question 77

What volume of 0.0500 M sodium hydroxide should be added to 250. mL of 0.100 M HCOOH to obtain a solution with a pH of 4.50? [K_a(HCOOH)= 1.7 * 10^-4]

A)540 mL
B)420 mL
C)80. mL
D)340 mL
E)500. mL

Question 78

Describe how to prepare 500. mL of a cyanic acid (HCNO)/sodium cyanate (NaCNO)buffer having a pH of 4.80. [K_a(HCNO)= 2.0 * 10^-4]

Question 79

Write a net ionic equation for the reaction that occurs when a small amount of nitric acid is added to a NaNO₂/HNO₂ buffer.

Question 80

Write a net ionic equation for the reaction occurring when a small amount of sodium hydroxide solution is added to a buffer solution containing NH₄Cl and NH₃.