Deck 16: Applications of Aqueous Equilibria

Question 1

What volume of 0.100 M NaOH is needed to make 100.0 mL of a buffer solution with a pH of 6.00 if one starts with 50.0 mL of 0.100 M potassium hydrogen phthalate? The K_a2 for potassium hydrogen phthalate is 3.1 × 10^-6.

A)22.4 mL
B)27.6 mL
C)30.2 mL
D)37.8 mL

Answer 1

37.8 mL

Question 2

What is the pH of a solution prepared by mixing 50.00 mL of 0.10 M NH₃ with 25.00 mL of 0.10 M NH₄Cl? Assume that the volume of the solutions are additive and that K_b = 1.8 × 10^-5 for NH₃.

A)8.95
B)9.26
C)9.56
D)11.13

Answer 2

9.56

Question 3

What is the approximate value of the equilibrium constant,K_n,for the neutralization of nitrous acid with ammonia,shown in the equation below? The K_a for HNO₂ is 4.5 × 10^-4 and the K_b for NH₃ is 1.8 × 10^-5. HNO₂(aq)+ NH₃(aq)⇌ NH₄NO₂(aq)

A)8.1 × 10⁵
B)1.8 × 10⁹
C)4.5 × 10¹⁰
D)8.1 × 10¹⁹

Answer 3

8.1 × 10⁵

Question 4

What is the pH of a buffer solution made by mixing 50.0 mL of 0.100 M potassium hydrogen phthalate with 13.6 mL of 0.100 M NaOH and diluting the mixture to 100.0 mL with water? The K_a2 for hydrogen phthalate is 3.1 × 10^-6.

A)3.25
B)5.08
C)5.51
D)5.94

Question 5

What is the pH of a buffered system made by dissolving 17.42 g of KH₂PO₄ and 20.41 g of K₂HPO₄ in water to give a volume of 200.0 mL? The K_a2 for dihydrogen phosphate is 6.2 × 10^-8 and the equilibrium reaction of interest is H₂PO₄^-(aq)+ H₂O(l)⇌ H₃O⁺(aq)+ HPO₄^-(aq).

A)7.03
B)7.17
C)7.38
D)7.58

Question 6

TRIS {(HOCH₂)₃CNH₂} is one of the most common buffers used in biochemistry.A solution is prepared by adding enough TRIS and 12 M HCl(aq)to give 1.00 L of solution with [TRIS] = 0.30 M and [TRISH⁺] = 0.60 M.What is the pH of this buffered system if the pK_b is 5.92?

A)5.92
B)6.22
C)7.78
D)8.08

Question 7

What is the hydronium ion concentration in a solution prepared by mixing 50.00 mL of 0.10 M HCN with 50.00 mL of NaCN? Assume that the volumes of the solutions are additive and that K_a = 4.9 × 10^-10 for HCN.

A)2.4 × 10^-10 M
B)4.9 × 10^-10 M
C)9.8 × 10^-10 M
D)7.0 × 10^-6 M

Question 8

What is the approximate value of the equilibrium constant,K_n,for the neutralization of pyridine with hydrochloric acid,shown in the equation below? The K_b for pyridine is 1.8 × 10^-9. HCl(aq)+ C₅H₅N(aq)⇌ C₅H₅NHCl(aq)

A)5.6 × 10^-10
B)5.6 × 10^-6
C)1.8 × 10⁵
D)5.6 × 10⁸

Question 9

What is the pH of a buffer system made by dissolving 10.70 grams of NH₄Cl and 20.00 mL of 12.0 M NH₃ in enough water to make 1.000 L of solution? K_b = 1.8 × 10^-5 for NH₃.

A)9.18
B)9.26
C)9.34
D)11.03

Question 10

Which statement about buffers is true?

A)Buffers have a pH = 7.
B)Buffers consist of a strong acid and its conjugate base.
C)A buffer does not change pH on addition of a strong acid or strong base.
D)Buffers resist change in pH upon addition of small amounts of strong acid or strong base.

Question 11

The neutralization constant K_n for the neutralization of acetylsalicylic acid (C₉H₈O₄)and codeine (C₁₈H₂₁NO₃)is 4.8 × 10⁴.The acid dissociation constant K_a for acetylsalicylic acid is 3.0 × 10^-4.What is the base dissociation constant K_b for codeine?

A)4.8 × 10^-24
B)6.3 × 10^-23
C)1.6 × 10^-6
D)1.4 × 10¹⁵

Question 12

The neutralization constant K_n for the neutralization of phenobarbital (C₁₂H₁₂N₂O₃)and morphine (C₁₇H₁₉NO₃)is 2.9.The acid dissociation constant K_a for phenobarbital is 3.9 × 10^-8.What is the base dissociation constant K_b for morphine?

A)1.3 × 10^-22
B)6.3 × 10^-23
C)7.4 × 10^-7
D)1.1 × 10⁷

Question 13

A buffer solution is prepared by dissolving 0.200 mol of NaH₂PO₄ and 0.100 mol of NaOH in enough water to make 1.00 L of solution.What is the pH of the H₂PO₄^-/HPO₄^2- buffer if the K_a2 = 6.2 × 10^-8?

A)6.91
B)7.21
C)7.51
D)7.71

Question 14

What is the [CH₃CO₂^-]/[CH₃CO₂H] ratio necessary to make a buffer solution with a pH of 4.44? K_a = 1.8 × 10^-5 for CH₃CO₂H.

A)0.50:1
B)0.94:1
C)1.1:1
D)2.0:1

Question 15

What is the pH of a solution prepared by mixing 25.00 mL of 0.10 M methylamine,CH₃NH₂,with 25.00 mL of 0.10 M methylammonium chloride,CH₃NH₃Cl? Assume that the volume of the solutions are additive and that K_b = 3.70 × 10^-4 for methylamine.

A)10.27
B)10.57
C)10.87
D)11.78

Question 16

What is the pH of 1 L of 0.30 M TRIS,0.60 M TRISH⁺ buffer to which one has added 5.0 mL of 12 M HCl? The K_b for the TRIS/TRISH⁺ is 1.2 × 10^-6.

A)5.92
B)6.36
C)7.36
D)7.64

Question 17

What is the resulting pH when 0.005 moles of KOH is added to 0.100 L of a buffer solution that is 0.100 M in H₂PO₄^- and 0.100 M HPO₄^2- and the K_a2 = 6.2 × 10^-8?

A)5.21
B)5.61
C)6.73
D)7.69

Question 18

What is the pH of a solution prepared by mixing 25.00 mL of 0.10 M CH₃CO₂H with 25.00 mL of 0.050 M CH₃CO₂Na? Assume that the volume of the solutions are additive and that K_a = 1.8 × 10^-5 for CH₃CO₂H.

A)2.87
B)4.44
C)4.74
D)5.05

Question 19

A buffer solution is prepared by dissolving 27.22 g of KH₂PO₄ and 3.37 g of KOH in enough water to make 0.100 L of solution.What is the pH of the H₂PO₄^-/HPO₄^2- buffer if the K_a2 = 6.2 × 10^-8?

A)6.84
B)7.00
C)7.21
D)7.84

Question 20

What is the magnitude of the change in pH when 0.005 moles of HCl is added to 0.100 L of a buffer solution that is 0.100 M in CH₃CO₂H and 0.100 M NaCH₃CO₂? The K_a for acetic acid is 1.8 × 10^-5.

A)0.00
B)0.20
C)0.47
D)1.30

Question 21

What is the Henderson-Hasselbalch equation for the acidic buffer HA/A^-?

A)pH = -log[H₃O⁺]
B)pH = 14 - pOH
C)pH = pK_a + log{[A^-]/[HA]}
D)pH = pK_a - log{[A^-]/[HA]}

Question 22

Which of the following buffer solutions will exhibit the highest pH?

A)0.100 M NH₃ with 0.100 M NH₄⁺
B)0.200 M NH₃ with 0.100 M NH₄⁺
C)0.200 M NH₃ with 0.0400M NH₄⁺
D)0.800 M NH₃ with 0.800 M NH₄⁺

Question 23

What is the approximate pH at the equivalence point of a weak acid-strong base titration if 25 mL of aqueous formic acid requires 29.80 mL of 0.0567 M NaOH? K_a = 1.8 × 10^-4 for formic acid.

A)2.46
B)5.88
C)8.12
D)11.54

Question 24

Formic acid (HCO₂H,K_a = 1.8 × 10^-4)is the principal component in the venom of stinging ants.What is the molarity of a formic acid solution if 25.00 mL of the formic acid solution requires 29.80 mL of 0.0567 M NaOH to reach the equivalence point?

A)0.0134 M
B)0.0476 M
C)0.0567 M
D)0.0676 M

Question 25

What is the approximate pH at the equivalence point of a weak acid-strong base titration if 25 mL of aqueous hydrofluoric acid requires 30.00 mL of 0.400 M NaOH? K_a = 6.76 × 10^-4 for HF.

A)1.74
B)5.75
C)8.25
D)12.26

Question 26

Consider a buffered solution consisting of H₂CO₃ and HCO₃^- where the pKa = 6.4.At pH = 6.4,which of the following is true?

A)[H₂CO₃] > [HCO₃^-]
B)[H₂CO₃]< [HCO₃^-]
C)[H₂CO₃] = [HCO₃^-]
D)[H₂CO₃] < [CO₃^-2]

Question 27

Which of the following mixtures would result in a buffered solution when 1.0 L of each of the two solutions are mixed.

A)0.2 M HNO₃ and 0.2 M NaNO₃
B)0.2 M HNO₃ and 0.4 M HF
C)0.2 M HNO₃ and 0.4 M NaF
D)0.2 M HNO₃ and 0.4 M NaOH

Question 28

At what pH is the amino acid glycine with a K_a of 2.51 × 10^-10 sixty-six (66%)percent dissociated?

A)9.60
B)9.89
C)10.10
D)10.60

Question 29

What is the pH of a solution made by mixing 30.00 mL of 0.10 M acetic acid with 40.00 mL of 0.10 M KOH? Assume that the volumes of the solutions are additive.K_a = 1.8 × 10^-5 for CH₃CO₂H.

A)8.26
B)9.26
C)11.13
D)12.15

Question 30

What is the pH at the equivalence point of a weak acid-strong base titration?

A)pH < 7
B)pH = 7
C)pH > 7
D)pH = 14.00

Question 31

What is not a correct expression for the weak acid HA?

A)K_a = [H₃O⁺][A^-]/[HA]
B)pK_a = pH - log{[A^-]/[HA]}
C)pK_a = logK_a
D)pK_a = 14 - pK_b

Question 32

What volume of 5.00 × 10^-3 M HNO₃ is needed to titrate 100.00 mL of 5.00 × 10^-3 M Ca(OH)₂ to the equivalence point?

A)12.5 mL
B)50.0 mL
C)100.mL
D)200.mL

Question 33

What is the pH of a solution made by mixing 30.00 mL of 0.10 M HCl with 40.00 mL of 0.10 M KOH? Assume that the volumes of the solutions are additive.

A)0.85
B)1.85
C)12.15
D)13.15

Question 34

Which is the best acid to use in the preparation of a buffer with pH = 3.3?

A)HOI (K_a = 2.0 × 10^-11)
B)HNO₂ (K_a = 4.5 × 10^-4)
C)HNO₃
D)HIO₃ (K_a = 1.7 × 10^-1)

Question 35

What is the pH of the resulting solution if 30.00 mL of 0.10 M acetic acid is added to 10.00 mL of 0.10 M NaOH? Assume that the volumes of the solutions are additive.K_a = 1.8 × 10^-5 for CH₃CO₂H.

A)9.56
B)8.95
C)5.05
D)4.44

Question 36

What is the percent dissociation of ascorbic acid if the solution has a pH = 5.50 and a pK_a = 4.10?

A)96%
B)10%
C)5%
D)1%

Question 37

Which is the best acid to use in the preparation of a buffer with pH = 9.3?

A)CH₃NH₂ (K_b = 3.7 × 10^-4)
B)NH₃ (K_b = 1.8 × 10^-5)
C)NH₂OH (K_b = 9.1 × 10^-9)
D)C₆H₅NH₂ (K_b = 4.3 × 10^-10)

Question 38

What is the percent dissociation of acetic acid if the solution has a pH = 4.74 and a pK_a = 4.74?

A)100%
B)50%
C)10%
D)1%

Question 39

What is the percent dissociation of glycine if the solution has a pH = 8.60 and a pK_a = 9.60?

A)50%
B)9%
C)5%
D)1%

Question 40

What is the pH of a solution made by mixing 30.00 mL of 0.10 M acetic acid with 30.00 mL of 0.10 M KOH? Assume that the volumes of the solutions are additive.K_a = 1.8 × 10^-5 for CH₃CO₂H.

A)5.28
B)7.00
C)8.72
D)10.02

Question 41

What is the molar solubility of AgCl in 0.10 M NH₃? K_sp for AgCl is 1.8 × 10^-10 and the K_f for Ag(NH₃)₂⁺ is 1.7 × 10⁷.

A)1.3 × 10^-5 M
B)5.0 × 10^-3 M
C)5.5 × 10^-3 M
D)5.5 × 10^-2 M

Question 42

Sodium hypochlorite,NaOCl,is the active ingredient in household bleach.What is the concentration of hypochlorite ion if 20.00 mL of bleach requires 28.30 mL of 0.500 M HCl to reach the equivalence point?

A)0.208 M
B)0.353 M
C)0.708 M
D)1.21 M

Question 43

Calculate the molar solubility of thallium(I)chloride in 0.30 M NaCl at 25°C.K_sp for TlCl is 1.7 × 10^-4.

A)5.1 × 10^-5 M
B)5.7 × 10^-4 M
C)7.1 × 10^-3 M
D)1.3 × 10^-2 M

Question 44

The dissociation equilibrium constants for the protonated form of alanine (a diprotic amino acid H₂X⁺)are K_a1 = 4.6 × 10^-3 and K_a2 = 2.0 × 10^-10.What is the pH of 50.00 mL of a 0.100 M solution of alanine after 100.00 mL of 0.100 M NaOH has been added?

A)9.70
B)10.69
C)11.11
D)12.70

Question 45

Barium hydroxide is slightly soluble in water,with a K_sp of 5.00 × 10^-4 at 298K.The dissolution of barium hydroxide in water is an endothermic process. Ba⁺² (aq)+ 2OH^- (aq)
Which of the following will increase the solubility?

A)Barium hydroxide is added to the solution.
B)Sodium hydroxide (NaOH)is added to the solution.
C)The temperature is decreased.
D)HCl is added to the mixture.(HCl reacts with OH-,removing it from the system. )

Question 46

What is the molar solubility of AgCl in 0.10 M NaCN if the colorless complex ion Ag(CN)₂^- forms? K_sp for AgCl is 1.8 × 10^-10 and K_f for Ag(CN)₂^- is 1.0 × 10²¹.

A)0.050 M
B)0.10 M
C)0.20 M
D)0.40 M

Question 47

The dissociation equilibrium constants for the protonated form of alanine (a diprotic amino acid,H₂X⁺)are K_a1 = 4.6 × 10^-3 and K_a2 = 2.0 × 10^-10.What is the pH of 50.00 mL of a 0.050 M solution of alanine after 37.50 mL of 0.100 M NaOH has been added?

A)4.85
B)6.02
C)7.39
D)9.70

Question 48

Oxalic acid,H₂C₂O₄ has acid dissociation constants K_a1 = 5.9 × 10^-2 and K_a2 = 6.4 × 10^-5.What is the pH after 20.00 mL of 0.0500 M NaOH is added to 5.00 mL of 0.2000 M H₂C₂O₄?

A)1.23
B)2.10
C)2.80
D)4.19

Question 49

What is the pH at the equivalence point of a weak base-strong acid titration if 20.00 mL of NaOCl requires 28.30 mL of 0.50 M HCl? K_a = 3.0 × 10^-8 for HOCl.

A)0.30
B)3.18
C)3.76
D)4.03

Question 50

Which of the following reactions are not consistent with the concept of acid base amphoterism?

A)Al(OH)₃(s)+ OH^-(aq)→ Al(OH)₄^-(aq)
B)Al(OH)₃(s)+ 3 H₃O⁺(aq)→ Al³⁺(aq)+ 6 H₂O(l)
C)H₂O(l)+ H₂O(l)⇌ H₃O⁺(aq)+ OH^-(aq)
D)Al(OH)₃(s)⇌ Al³⁺(aq)+ 3 OH^-(aq)

Question 51

What is the molar solubility of CaF₂ in 0.10 M NaF solution at 25°C? The K_sp for CaF₂ is 3.4 × 10^-11.

A)8.5 × 10^-10 M
B)3.4 × 10^-10 M
C)3.4 × 10^-9 M
D)2.0 × 10^-4 M

Question 52

What is the molar solubility of AgCl in 1.0 M K₂S₂O₃ if the complex ion Ag(S₂O₃)₂^3- forms? The Ksp for AgCl is 1.8 × 10^-10 and the K_f for Ag(S₂O₃)₂^3- is 2.9 × 10¹³.

A)0.50 M
B)1.0 M
C)1.5 M
D)2.0 M

Question 53

What is the molar solubility of Mg(OH)₂ in a basic solution with a pH of 12.00? K_sp for Mg(OH)₂ is

A)5.6 × 10^-10 M
B)5.6 × 10^-8 M
C)2.4 × 10^-6 M
D)1.1 × 10^-4 M

Question 54

Calculate the solubility (in g/L)of silver carbonate in water at 25°C if the K_sp for Ag₂CO₃ is 8.4 × 10^-12.

A)8.0 × 10^-4 g/L
B)3.5 × 10^-2 g/L
C)4.4 × 10^-2 g/L
D)5.6 × 10^-2 g/L

Question 55

Calculate the K_sp for silver sulfate if the solubility of Ag₂SO₄ in pure water is 4.5 g/L.

A)3.0 × 10^-6
B)1.2 × 10^-5
C)2.1 × 10^-4
D)4.2 × 10^-4

Question 56

Sulfurous acid,H₂SO₃ has acid dissociation constants K_a1 = 1.5 × 10^-2 and K_a2 = 6.3 × 10^-8.What is the pH after 10.00 mL of 0.1000 M NaOH is added to 10.00 mL of 0.1000 M H₂SO₃?

A)1.82
B)3.60
C)4.25
D)7.20

Question 57

Which of the following metal hydroxides are amphoteric?

A)Al(OH)₃,Zn(OH)₂,Cr(OH)₃,Sn(OH)₂
B)Cu(OH)₂,Mn(OH)₂,Fe(OH)₂,Fe(OH)₃
C)Be(OH)₂,Ca(OH)₂,Ba(OH)₂,Sr(OH)₃
D)LiOH,NaOH,KOH,RbOH

Question 58

What is the pH of the resulting solution if 25 mL of 0.432 M methylamine,CH₃NH₂,is added to 15 mL of 0.234 M HCl? Assume that the volumes of the solutions are additive.K_a = 2.70 × 10^-11 for CH₃NH₃⁺.

A)3.11
B)3.74
C)10.26
D)10.89

Question 59

What is the molar solubility of lead(II)chromate in 0.10 M HNO₃ if the K_sp for PbCrO₄ is 2.8 × 10^-13 and the K_a2 for H₂CrO₄ is 3.0 × 10^-7? Note that H₂CrO₄ is considered to be a strong acid.

A)9.2 × 10^-11 M
B)2.9 × 10^-10 M
C)9.3 × 10^-7 M
D)3.1 × 10^-4 M

Question 60

The dissociation equilibrium constants for the protonated form of alanine (a diprotic amino acid,H₂X⁺)are K_a1 = 4.6 × 10^-3 and K_a2 = 2.0 × 10^-10.What is the pH of 50.00 mL of a 0.0500 M solution of alanine after 25.00 mL of 0.100 M NaOH has been added?

A)2.34
B)4.85
C)5.59
D)6.72

Question 61

The following pictures represent solutions that contain a weak acid HA (pK_a = 5.0)and its potassium salt KA.Unshaded spheres represent H atoms and shaded spheres represent A^- ions.(K⁺,H₃O⁺,OH^-,and solvent H₂O molecules have been omitted for clarity. )
Which solution has the highest pH?

A)(1)
B)(2)
C)(3)
D)(4)

Question 62

The following pictures represent solutions that contain a weak acid HA and/or its potassium salt KA.Unshaded spheres represent H atoms and shaded spheres represent A^- ions.(K⁺,H₃O⁺,OH^-,and solvent H₂O molecules have been omitted for clarity. )
Which solution has the lowest pH?

A)(1)
B)(2)
C)(3)
D)(4)

Question 63

The following pictures represent solutions that contain a weak acid HA (pK_a = 5.0)and its potassium salt KA.Unshaded spheres represent H atoms and shaded spheres represent A^- ions.(K⁺,H₃O⁺,OH^-,and solvent H₂O molecules have been omitted for clarity. )
Which of these solutions are buffers?

A)(1)and (2)
B)(1)and (3)
C)(1), (2)and (3)
D)All are buffer solutions.

Question 64

A solution may contain the following ions Ag⁺,Cu²⁺,Mn²⁺,Ca²⁺,and Na⁺.No precipitate formed when 0.10 M NaCl was added but a dark colored precipitate formed when H₂S was added to an acidic portion of the solution.After the removal of the solid the solution was made basic and more H₂S was added and a dark precipitate again formed.Treatment of the filtrate with (NH₄)₂CO₃ resulted in a white precipitate.If no further tests were made then what conclusions can you draw?

A)possible ions present Cu²⁺,Mn²⁺,Na⁺
B)possible ions present Cu²⁺,Mn²⁺,Ca²⁺
C)possible ions present Cu²⁺,Mn²⁺,Ca²⁺,Na⁺
D)possible ions present Ag⁺,Cu²⁺,Mn²⁺,Ca²⁺,Na⁺

Question 65

0.10 M potassium chromate is slowly added to a solution containing 0.20 M AgNO₃ and 0.20 M Ba(NO₃)₂.What is the Ag⁺ concentration when BaCrO₄ just starts to precipitate? K_sp for Ag₂CrO₄ and BaCrO₄ are 1.1 × 10^-12 and 1.2 × 10^-10,respectively.

A)6.5 × 10^-5 M
B)1.3 × 10^-4 M
C)3.2 × 10^-4 M
D)4.3 × 10^-2 M

Question 66

Which metal sulfides can be precipitated from a solution that is 0.01 M in Mn²⁺,Zn²⁺,Pb²⁺ and Cu²⁺ and 0.10 M in H₂S at a pH of 0.50?

A)MnS
B)CuS
C)PbS,CuS
D)ZnS,PbS,CuS

Question 67

The following pictures represent solutions that contain a weak acid HA and/or its potassium salt KA.Unshaded spheres represent H atoms and shaded spheres represent A^- ions.(K⁺,H₃O⁺,OH^-,and solvent H₂O molecules have been omitted for clarity. )
Which of the solutions are buffer solutions?

A)(1)and (2)
B)(1)and (3)
C)(2)and (3)
D)(2)and (4)

Question 68

The following pictures represent solutions that contain a weak acid HA and/or its potassium salt KA.Unshaded spheres represent H atoms and shaded spheres represent A^- ions.(K⁺,H₃O⁺,OH^-,and solvent H₂O molecules have been omitted for clarity. )
Which solution has the greatest buffer capacity?

A)(1)
B)(2)
C)(3)
D)(4)

Question 69

The following pictures represent solutions that contain a weak acid HA (pK_a = 5.0)and its potassium salt KA.Unshaded spheres represent H atoms and shaded spheres represent A^- ions.(K⁺,H₃O⁺,OH^-,and solvent H₂O molecules have been omitted for clarity. )
Which solution has the greatest buffer capacity?

A)(1)
B)(2)
C)(3)
D)(4)

Question 70

The following pictures represent solutions that contain a weak acid HA and/or its potassium salt KA.Unshaded spheres represent H atoms and shaded spheres represent A^- ions.(K⁺,H₃O⁺,OH^-,and solvent H₂O molecules have been omitted for clarity. )
Which solution has the largest percent dissociation of HA?

A)(1)
B)(2)
C)(3)
D)(4)

Question 71

The following pictures represent solutions that contain a weak acid HA (pK_a = 5.0)and its potassium salt KA.Unshaded spheres represent H atoms and shaded spheres represent A^- ions.(K⁺,H₃O⁺,OH^-,and solvent H₂O molecules have been omitted for clarity. )
Which solution has the largest percent dissociation of HA?

A)(1)
B)(2)
C)(3)
D)(4)

Question 72

The following pictures represent solutions that contain a weak acid HA (pK_a = 5.0)and its potassium salt KA.Unshaded spheres represent H atoms and shaded spheres represent A^- ions.(K⁺,H₃O⁺,OH^-,and solvent H₂O molecules have been omitted for clarity. )
Which solution has the lowest pH?

A)(1)
B)(2)
C)(3)
D)(4)

Question 73

The following pictures represent solutions that contain a weak acid HA (pK_a = 5.0)and its potassium salt KA.Unshaded spheres represent H atoms and shaded spheres represent A^- ions.(K⁺,H₃O⁺,OH^-,and solvent H₂O molecules have been omitted for clarity. )
For which of these solutions is pH = pK_a?

A)All have pH = pK_a.
B)(1), (2)and (3)
C)(1)and (4)
D)(2)and (3)

Question 74

Precipitation of an ionic compound will occur upon mixing of desired reagents if the initial ion product is

A)greater than the K_sp.
B)equal to the pK_sp.
C)equal to the K_sp.
D)less than the K_sp.

Question 75

Potassium chromate is slowly added to a solution containing 0.20 M AgNO₃ and 0.20 M Ba(NO₃)₂.Describe what happens if the K_sp for Ag₂CrO₄ is 1.1 × 10^-12 and the K_sp of BaCrO₄ is 1.2 × 10^-10.

A)The BaCrO₄ precipitates first out of solution.
B)The Ag₂CrO₄ precipitates first out of solution and then BaCrO₄ precipitates.
C)Both BaCrO₄ and Ag₂CrO₄ precipitate simultaneously out of solution.
D)Neither BaCrO₄ nor Ag₂CrO₄ precipitates out of solution.

Question 76

The following pictures represent solutions that contain a weak acid HA and/or its potassium salt KA.Unshaded spheres represent H atoms and shaded spheres represent A^- ions.(K⁺,H₃O⁺,OH^-,and solvent H₂O molecules have been omitted for clarity. )
For which solution(s)is pH = pK_a?

A)only solution (1)
B)only solution (2)
C)only solution (3)
D)solutions (1)and (3)

Question 77

The following pictures represent solutions that contain a weak acid HA (pK_a = 5.0)and its potassium salt KA.Unshaded spheres represent H atoms,black spheres represent oxygen atoms,and shaded spheres represent A^- ions.(K⁺,H₃O⁺ initially present,OH^- initially present and solvent water molecules have been omitted for clarity. )
Which picture represents the equilibrium state of the solution after addition of one H₃O⁺ ion to the solution shown in picture (1)?

A)(2)
B)(3)
C)(4)
D)(5)

Question 78

A solution may contain the following ions Ag⁺,Cu²⁺,Cd²⁺,Mn²⁺,Ni²⁺ and Na⁺.A white precipitate formed when 0.10 M NaCl was added and after this was removed the solution was treated with H₂S gas under acidic conditions and no precipitate formed.When the solution was made basic and again treated with H₂S gas a dark colored precipitate formed.If no further tests were made then what conclusions can you draw?

A)possible ions present Ag⁺,Mn²⁺,Ni²⁺
B)possible ions present Ag⁺,Mn²⁺,Ni²⁺,Na⁺
C)possible ions present Ag⁺,Cu²⁺,Cd²⁺
D)possible ions present Ag⁺,Cu²⁺,Cd²⁺,Na⁺

Question 79

The following pictures represent solutions that contain a weak acid HA and/or its potassium salt KA.Unshaded spheres represent H atoms and shaded spheres represent A^- ions.(K⁺,H₃O⁺,OH^-,and solvent H₂O molecules have been omitted for clarity. )
Which solution has the highest pH?

A)(1)
B)(2)
C)(3)
D)(4)

Question 80

Which metal sulfides can be precipitated from a solution that is 0.01 M in Mn²⁺,Zn²⁺,Pb²⁺ and Cu²⁺ and 0.10 M in H₂S at a pH of 1.0?

A)MnS
B)CuS
C)PbS,CuS
D)ZnS,PbS,CuS