CHE 107 Fall 2017 Exam 3

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Question #: 1

What is the pH of a 0.15 M NaOH solution? pH = 1 Report your answer with two DECIMAL places. Do NOT include units in your answer.

1.

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Question #: 2

What is the pH of a 0.25 M solution of cyanic acid, HCNO at 25ºC? The Ka of HCNO at 25ºC is 3.5 ×10–4. .

A. 2.03

B. 1.57

C. 4.95

D. 8.18

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Question #: 3

What is the pH of a 0.20 M HNO2 solution if the percent ionization is 1.2%? .

A. 3.70

B. 1.91

C. 2.62

D. 4.25

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Question #: 4

What is the pH of a solution that is 0.10 M in HNO2 (Ka = 4.5 × 10–4) and 0.10 M in HNO3? Report your answer to two DECIMAL places. Do NOT include units in your answer. pH = 1

1.

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Question #: 5

Morphine, C17H19O3N, is pain medication naturally found in plants. What is the pH of a solution containing 0.15 M C17H19O3N when Kb= 7.4 × 10–7? pH = 1 Report your answer with two DECIMAL places. Do NOT include units in your answer.

1.

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Question #: 6

What is the value of the equilibrium constant for reaction shown below? The Ka of hydrocyanic acid, HCN is 4.9 × 10–10 at 25 ºC. CN–(aq) + H2O(l) ⇔ HCN(aq) + OH–(aq) .

A. 4.9 × 10–10

B. 2.0 × 10–5

C. 2.8 × 10–10

D. 1.0 × 10–14

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Question #: 7

Select two salts that give solutions with pH <7 when dissolved in water.

A. MgF2

B. NH4Cl

C. LiClO4

D. NaNO2

E. CH3NH3Br

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Question #: 8

Which pair has the stronger acid listed first?

A. H2Te, HCl

B. H2O, HF

C. H2S, H2Te

D. H2Se, H2O

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Question #: 9

Which comparison of acidities is false?

A. HClO3 is a stronger acid than HClO2.

B. H2SeO3 is a stronger acid than H2TeO3.

C. HClO3 is a stronger acid than HIO3.

D. H3PO3 is a stronger acid than H3PO4.

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Question #: 10

Which two compounds act as Lewis acids in the following reactions?

A. diethyl ether

B. aluminum trichloride

C. calcium oxide

D. sulfur trioxide

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Question #: 11

Which two pairs can act as a buffer in aqueous solution? Concentrations of all substances are 0.10 M.

A. HNO3 and LiOH

B. HCl and KCl

C. HCN and LiCN

D. HIO and H2O

E. H2SO3 and K2SO3

F. NaH2PO4 and Na2HPO4

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Question #: 12

What is the pH of a 1.00 L solution containing 0.295 M lactic acid, HC3H5O3 (pKa = 3.86) and 0.295 M sodium lactate, NaC3H5O3, upon the addition of 0.055 mol HCl? Assume no significant volume change occurs. .

A. 3.86

B. 4.02

C. 3.59

D. 3.70

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Question #: 13

Which combination is best for preparing a pH 8.75 buffer?

A. acetic acid (pKa = 4.74) and sodium acetate

B. sodium hydrogen chromate (pKa = 6.52) and sodium chromate

C. hypochlorous acid (pKa = 7.54) and sodium hypochlorite

D. ammonium chloride (pKa = 9.25) and ammonia

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Question #: 14

What is the pH at the equivalence point when 50.0 mL formic acid, HCHO2, is titrated with 50.0 mL 0.100 M NaOH? The Ka for formic acid is 1.8 × 10–4 at 25 ºC. .

A. 7.00

B. 5.77

C. 7.72

D. 8.22

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Question #: 15

A 25.0 mL portion of 0.200 M HF (pKa = 3.17) is titrated with 2.00 M KOH. What is the pH halfway to the equivalence point?

pH = 1 Report your answer with two DECIMAL places. Do NOT include units in your answer.

1.

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Question #: 16

A 25.0 mL portion of 0.200 M HF (pKa = 3.17) is titrated with 2.00 M KOH. What is the pH after the addition of 1.00 mL KOH?

pH = 1 Report your answer with two DECIMAL places. Do NOT include units in your answer.

1.

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Question #: 17

Which graph best represents the titration of a weak, monoprotic acid with a strong base? Enter the letter corresponding to the correct graph 1

1.

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Question #: 18

Alizarin yellow R, an indicator with a pKa of 11.0, is red in its basic form and yellow in its acidic form. What color will a solution appear if the [In–]/[HIn] is 0.015?

A. red

B. yellow

C. orange

D. purple

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Question #: 19

Which indicator is most suitable for detecting the endpoint of a titration of a weak base with a strong acid?

Indicator Name pKa pH Range Color Change

methyl red 5.4 4.8-6.0 red to yellow

cresol red 7.9 7.0-8.8 yellow to red

thymol blue 8.8 8.0-9.6 yellow to blue

phenolphthalein 9.1 8.2-10.0 colorless to pink

A. methyl red

B. cresol red

C. thymol blue

D. phenolphthalein

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Question #: 20

Which choice ranks the salts in order from least to greatest molar solubility given the information below? Ag2S, Ksp = 6.0 ×10–51 CaF2, Ksp = 1.5 ×10–10 Cd(OH)2, Ksp = 2.5 ×10–14 Mg(OH)2, Ksp = 1.8 ×10–11 .

A. Ag2S < CaF2< Mg(OH)2< Cd(OH)2

B. Ag2S < Cd(OH)2< Mg(OH)2< CaF2

C. CaF2 < Mg(OH)2< Cd(OH)2< Ag2S

D. CaF2 < Ag2S < Cd(OH)2< Mg(OH)2

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Question #: 21

Which 0.10 M solution increases the solubility of CaCO3(s)? .

A. HCl(aq)

B. NaF(aq)

C. KOH(aq)

D. MgI2(aq)

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Question #: 22

What is the molar solubility of CaF2 (Ksp = 1.46 × 10–10) in a solution containing 0.35 M NaF? .

A. 1.46 × 10–12 M

B. 3.32 × 10–4 M

C. 1.19 × 10–9 M

D. 4.17 × 10–10 M

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Question #: 23

What happens when two solutions are mixed such that final concentrations are 0.010 M K2SO4 and 0.020 M CaCl2? Ksp(CaSO4) = 9.1 × 10–6 .

A. Nothing happens since K2SO4 and CaCl2 are both soluble.

B. Some CaSO4 will precipitate out of solution, leaving a saturated solution.

C. Some CaSO4 will precipitate out of solution, leaving an unsaturated solution.

D. All CaSO4 will remain dissolved, resulting in an unsaturated solution.

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Question #: 24

A solution containing 0.10 M Ba2+ and 0.10 M Zn2+ is titrated with a concentrated potassium oxalate solution. Assuming minimal volume changes, which solid precipitates first and what concentration of C2O42– is required? The Ksp for BaC2O4 is 1.6 × 10–6 and for ZnC2O4 is 2.7 × 10–8. .

A. BaC2O4, 1.6 × 10–5 M

B. BaC2O4, 2.7 × 10–7 M

C. ZnC2O4, 1.6 × 10–5 M

D. ZnC2O4, 2.7 × 10–7 M

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Question #: 25

Solid Na2S is slowly added to a solution that is 0.010 M in Cd2+ and 0.010 M in Ni2+. What is the concentration of Cd2+ remaining when Ni2+ begins to precipitate? CdS, Ksp = 8.0 ×10–28 NiS, Ksp = 3.0 ×10–20 .

A. 2.7 × 10–7 M Cd2+

B. 8.5 ×10–15 M Cd2+

C. 7.4 × 10–12 M Cd2+

D. 2.7 × 10–10 M Cd2+

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Question #: 26

For the coordination compound [Co(NH3)4(OH)2]Cl The charge on Co is 1 . The coordination number of Co is 2 .

1.

2.

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Question #: 27

Crystal-field diagrams of [Fe(H2O)6]2+ (left) and [Fe(CN)6]4– (right) are shown below. From the diagram, we can tell that H2O is a 1 [strong, weak]-field ligand while CN– is a 2 [strong, weak]-field ligand. If the oxidation state of [Fe(H2O)6]2+ were increased from +2 to +3, the crystal field splitting energy, Δ, would become 3 [larger, smaller].

1.

2.

3.

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Question #: 28

F– is a weak field ligand. There are 1 unpaired electrons in the complex ion [CoF6]3–, making the complex 2 [paramagnetic, diamagnetic].

1.

2.

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Question #: 29

A solution is prepared such that it contains 0.010 M Sn(NO3)4 and 0.100 M NaF. What concentration of Sn4+(aq) remains once the reaction reaches equilibrium according to the equation below? Sn4+(aq) + 6 F–(aq) ⇔ [SnF6]2–(aq) Kf = 1.0 ×1025 .

A. 9.7 × 10–28 M

B. 6.2 × 10–22 M

C. 2.4 × 10–19 M

D. 1.9 ×10–12 M

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Question #: 30

Which compound will increase the solubility of ZnCO3? .

Complex Ion Kf

Zn(CN)42– 2.1 ×1019

Zn(NH3)42+ 2.8 ×109

Zn(OH)42– 2.0 ×1015

A. NaCl

B. KNO3

C. NaCN

D. LiBr

DRAFTDo Not Use Until Posted.

CHE 107 Fall 2017 Exam 3 - Confidential

Your Name: Your ID:

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Question #: 1

What is the pH of a 0.15 M NaOH solution?

pH =     1    

Report your answer with two DECIMAL places. Do NOT include units in your answer.

1. 13.18

Question #: 2

What is the pH of a 0.25 M solution of cyanic acid, HCNO at 25ºC?

The Ka of HCNO at 25ºC is 3.5 ×10–4.

.

✓A. 2.03 B. 1.57 C. 4.95 D. 8.18

Question #: 3

What is the pH of a 0.20 M HNO2 solution if the percent ionization is 1.2%?

.

A. 3.70 B. 1.91

✓C. 2.62 D. 4.25

Question #: 4

What is the pH of a solution that is 0.10 M in HNO2 (Ka = 4.5 × 10–4) and 0.10 M in HNO3? 

Report your answer to two DECIMAL places. Do NOT include units in your answer.

pH =     1    

1. 1.00

Question #: 5

Morphine, C17H19O3N, is pain medication naturally found in plants. What is the pH of a

solution containing 0.15 M C17H19O3N when Kb= 7.4 × 10–7?

pH =     1    

Report your answer with two DECIMAL places. Do NOT include units in your answer.

1. 10.52

Question #: 6

What is the value of the equilibrium constant for reaction shown below? The Ka of hydrocyanic

acid, HCN is 4.9 × 10–10 at 25 ºC.

CN–(aq) + H2O(l) ⇔ HCN(aq) + OH–(aq)

.

A. 4.9 × 10–10

✓B. 2.0 × 10–5

C. 2.8 × 10–10

D. 1.0 × 10–14

Question #: 7

Select two salts that give solutions with pH <7 when dissolved in water.

A. MgF2

✓B. NH4Cl C. LiClO4 D. NaNO2

✓E. CH3NH3Br

Question #: 8

Which pair has the stronger acid listed first?

A. H2Te, HCl B. H2O, HF C. H2S, H2Te

✓D. H2Se, H2O

Question #: 9

Which comparison of acidities is false?

A. HClO3 is a stronger acid than HClO2. B. H2SeO3 is a stronger acid than H2TeO3. C. HClO3 is a stronger acid than HIO3.

✓D. H3PO3 is a stronger acid than H3PO4.

Question #: 10

Which two compounds act as Lewis acids in the following reactions?

A. diethyl ether

✓B. aluminum trichloride C. calcium oxide

✓D. sulfur trioxide

Question #: 11

Which two pairs can act as a buffer in aqueous solution? Concentrations of all substances are

0.10 M.

A. HNO3 and LiOH B. HCl and KCl

✓C. HCN and LiCN D. HIO and H2O E. H2SO3 and K2SO3

✓F. NaH2PO4 and Na2HPO4

Question #: 12

What is the pH of a 1.00 L solution containing 0.295 M lactic acid, HC3H5O3 (pKa = 3.86) and

0.295 M sodium lactate, NaC3H5O3, upon the addition of 0.055 mol HCl? Assume no significant

volume change occurs.

.

A. 3.86 B. 4.02 C. 3.59

✓D. 3.70

Question #: 13

Which combination is best for preparing a pH 8.75 buffer?

A. acetic acid (pK

a = 4.74) and sodium acetate 

B. sodium hydrogen chromate (pKa

 = 6.52) and sodium chromate C. hypochlorous acid (pK

a = 7.54) and sodium hypochlorite

✓D. ammonium chloride (pKa

 = 9.25) and ammonia

Question #: 14

What is the pH at the equivalence point when 50.0 mL formic acid, HCHO2, is titrated with 50.0

mL 0.100 M NaOH? The Ka for formic acid is 1.8 × 10–4 at 25 ºC.

.

A. 7.00 B. 5.77 C. 7.72

✓D. 8.22

Question #: 15

A 25.0 mL portion of 0.200 M HF (pKa = 3.17) is titrated with 2.00 M KOH. What is the pH

halfway to the equivalence point? 

pH =     1    

Report your answer with two DECIMAL places. Do NOT include units in your answer.

1. 3.17

Question #: 16

A 25.0 mL portion of 0.200 M HF (pKa = 3.17) is titrated with 2.00 M KOH. What is the pH

after the addition of 1.00 mL KOH? 

pH =     1    

Report your answer with two DECIMAL places. Do NOT include units in your answer.

1. 2.99

Question #: 17

Which graph best represents the titration of a weak, monoprotic acid with a strong base? Enter

the letter corresponding to the correct graph     1    

 

  

 

1. C

Question #: 18

Alizarin yellow R, an indicator with a pKa of 11.0, is red in its basic form and yellow in its acidic

form. What color will a solution appear if the [In–]/[HIn] is 0.015?

A. red ✓B. yellow

C. orange D. purple

Question #: 19

Which indicator is most suitable for detecting the endpoint of a titration of a weak base with a

strong acid?

 

✓A. methyl red

B. cresol red C. thymol blue D. phenolphthalein

Question #: 20

Which choice ranks the salts in order from least to greatest molar solubility given the

information below?

Ag2S, Ksp = 6.0 ×10–51 

CaF2, Ksp = 1.5 ×10–10

Cd(OH)2, Ksp = 2.5 ×10–14

Mg(OH)2, Ksp = 1.8 ×10–11 .

A. Ag

2S < CaF

2< Mg(OH)

2< Cd(OH)

2 ✓B. Ag

2S < Cd(OH)

2< Mg(OH)

2< CaF

2 C. CaF

2 < Mg(OH)

2< Cd(OH)

2< Ag

2S

Indicator Name pKa pH Range Color Change

methyl red 5.4 4.8-6.0 red to yellow

cresol red 7.9 7.0-8.8 yellow to red

thymol blue 8.8 8.0-9.6 yellow to blue

phenolphthalein 9.1 8.2-10.0 colorless to pink

D. CaF2 < Ag

2S < Cd(OH)

2< Mg(OH)

2

Question #: 21

Which 0.10 M solution increases the solubility of CaCO3(s)?

.

✓A. HCl(aq)

B. NaF(aq) C. KOH(aq) D. MgI2(aq)

Question #: 22

What is the molar solubility of CaF2 (Ksp = 1.46 × 10–10) in a solution containing 0.35 M NaF?

.

 

A. 1.46 × 10–12 M B. 3.32 × 10–4 M

✓C. 1.19 × 10–9 M D. 4.17 × 10–10 M

Question #: 23

What happens when two solutions are mixed such that final concentrations are 0.010 M K2SO4and 0.020 M CaCl2?

Ksp(CaSO4) = 9.1 × 10–6 .

A. Nothing happens since K2SO4 and CaCl2 are both soluble.

✓B. Some CaSO4 will precipitate out of solution, leaving a saturated solution. C. Some CaSO4 will precipitate out of solution, leaving an unsaturated solution. D. All CaSO4 will remain dissolved, resulting in an unsaturated solution.

Question #: 24

A solution containing 0.10 M Ba2+ and 0.10 M Zn2+ is titrated with a concentrated potassium

oxalate solution. Assuming minimal volume changes, which solid precipitates first and what

concentration of C2O42– is required? The Ksp for BaC2O4 is 1.6 × 10–6 and for ZnC2O4 is 2.7

× 10–8. 

.

A. BaC2O4, 1.6 × 10–5 M B. BaC2O4, 2.7 × 10–7 M C. ZnC2O4, 1.6 × 10–5 M

✓D. ZnC2O4, 2.7 × 10–7 M

Question #: 25

Solid Na2S is slowly added to a solution that is 0.010 M in Cd2+ and 0.010 M in Ni2+. What is

the concentration of Cd2+ remaining when Ni2+ begins to precipitate?

CdS, Ksp = 8.0 ×10–28

NiS, Ksp = 3.0 ×10–20 .

A. 2.7 × 10–7 M Cd

2+

B. 8.5 ×10–15 M Cd2+

C. 7.4 × 10–12 M Cd

2+

✓D. 2.7 × 10–10 M Cd2+

Question #: 26

For the coordination compound [Co(NH3)4(OH)2]Cl

The charge on Co is     1    . 

The coordination number of Co is     2    .

1. 3|+3|

2. 6

Question #: 27

Crystal-field diagrams of [Fe(H2O)6]2+ (left) and [Fe(CN)6]4– (right) are shown below.

From the diagram, we can tell that H2O is a     1     [strong, weak]-field ligand while CN– is a 

    2     [strong, weak]-field ligand.

If the oxidation state of [Fe(H2O)6]2+ were increased from +2 to +3, the crystal field splitting

energy, Δ, would become     3     [larger, smaller].

1. weak

2. strong

3. larger

Question #: 28

F– is a weak field ligand. There are     1     unpaired electrons in the complex ion [CoF6]3–,

making the complex     2     [paramagnetic, diamagnetic].

1. 4

2. paramagnetic

Question #: 29

A solution is prepared such that it contains 0.010 M Sn(NO3)4 and 0.100 M NaF. What

concentration of Sn4+(aq) remains once the reaction reaches equilibrium according to the

equation below?

Sn4+(aq) + 6 F–(aq) ⇔ [SnF6

]2–(aq)    Kf = 1.0 ×1025 .

A. 9.7 × 10–28 M  B. 6.2 × 10–22 M

✓C. 2.4 × 10–19 M D. 1.9 ×10–12 M

Question #: 30

Which compound will increase the solubility of ZnCO3?

.

 

A. NaCl B. KNO3

✓C. NaCN D. LiBr

Complex Ion KfZn(CN)4

2– 2.1 ×1019

Zn(NH3)42+ 2.8 ×109

Zn(OH)42– 2.0 ×1015