Upload
others
View
2
Download
0
Embed Size (px)
Citation preview
CHE 107 Fall 2017 Exam 3
Your Name: Your ID:
____________________________________________________________________________
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.
____________________________________________________________________________
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.
____________________________________________________________________________
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.
____________________________________________________________________________
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 (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
____________________________________________________________________________
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.
____________________________________________________________________________
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.
____________________________________________________________________________
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.
____________________________________________________________________________
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?
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
____________________________________________________________________________
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
____________________________________________________________________________
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 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.
____________________________________________________________________________
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 Cd2+
B. 8.5 ×10–15 M Cd2+
C. 7.4 × 10–12 M Cd2+
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.
2.
____________________________________________________________________________
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.
____________________________________________________________________________
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.
____________________________________________________________________________
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? .
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:
attachment_for_pubExamUID_lnxp115107596682339825XX_232.jpg
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