Question 1

Which statement about buffers is true?

Accepted Answer

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. 
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 2

Which set of ions precipitate as sulfides?

Accepted Answer

A) Ag+,Pb2+,Mn2+ 
B) Pb2+,Fe2+,Ca2+ 
C) Co2+,Ba2+,K+ 
D) NH4+,Na+,K+ 
A) Ag+,Pb2+,Mn2+ 
B) Pb2+,Fe2+,Ca2+ 
C) Co2+,Ba2+,K+ 
D) NH4+,Na+,K+

Question 3

Which pair of ions can be separated by the addition of chloride ion?

Accepted Answer

A) Ag+ and Co2+ 
B) Cu2+ and Bi3+ 
C) Pb2+ and Hg22+ 
D) Ca2+ and Ba2+ 
A) Ag+ and Co2+ 
B) Cu2+ and Bi3+ 
C) Pb2+ and Hg22+ 
D) Ca2+ and Ba2+

Question 4

The dissociation equilibrium constants for the protonated form of alanine (a diprotic amino acid,H2X+)are Ka1 = 4.6 × 10-3 and Ka2 = 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?

Accepted Answer

A) 4)85 
B) 6)02 
C) 7)39 
D) 9)70 
A) 4)85 
B) 6)02 
C) 7)39 
D) 9)70

Question 5

Which is a net ionic equation for the neutralization of a weak acid with a strong base?

Accepted Answer

A) HCl(aq)+ NaOH(aq)⇌ H2O(l)+ NaCl(aq) 
B) H3O+(aq)+ OH-(aq)⇌ 2 H2O(l) 
C) HF(aq)+ NaOH(aq)⇌ H2O(l)+ NaF(aq) 
D) HF(aq)+ OH-(aq)⇌ H2O(l)+ F-(aq) 
A) HCl(aq)+ NaOH(aq)⇌ H2O(l)+ NaCl(aq) 
B) H3O+(aq)+ OH-(aq)⇌ 2 H2O(l) 
C) HF(aq)+ NaOH(aq)⇌ H2O(l)+ NaF(aq) 
D) HF(aq)+ OH-(aq)⇌ H2O(l)+ F-(aq)

Question 6

The following plot shows two titration curves,each representing the titration of 50.00 mL of 0.100 M acid with 0.100 M NaOH.  
-Which point a-d represents the equivalence point for the titration of a strong acid?

Accepted Answer

A) point a 
B) point b 
C) point c 
D) point d 
A) point a 
B) point b 
C) point c 
D) point d

Question 7

The following pictures represent solutions of CaCOS1U1B13S1U1B0,which may also contain ions other than CaS1U1P12+S1S1P0 and COS1U1B13S1U1B0S1U1P12-S1S1P0 which are not shown.Gray spheres represent CaS1U1P12+S1S1P0 ions and unshaded spheres represent COS1U1B13S1U1B0S1U1P12-S1S1P0 ions.  
-If solution (1)is a saturated solution of CaCO3,which of solutions (1)-(4)represents the solution after a small amount of Ca(NO3)2 is added and equilibrium is restored?

Accepted Answer

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

Question 8

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?

Accepted Answer

A) 0)208 M 
B) 0)353 M 
C) 0)708 M 
D) 1)21 M 
A) 0)208 M 
B) 0)353 M 
C) 0)708 M 
D) 1)21 M

Question 9

What is the equation relating the equilibrium constant Kn for the neutralization of a weak acid with a weak base to the Ka of the acid,the Kb of the base and Kw?

Accepted Answer

A) Kn = KaKbKw 
B) Kn =   
C) Kn =   
D) Kn =   
A) Kn = KaKbKw 
B) Kn =   
C) Kn =   
D) Kn =

Question 10

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 Ka2 for dihydrogen phosphate is 6.2 × 10-8 and the equilibrium reaction of interest is
H2PO4-(aq)+ H2O(l)⇌ H3O+(aq)+ HPO4-(aq).

Accepted Answer

A) 7)03 
B) 7)17 
C) 7)38 
D) 7)58 
A) 7)03 
B) 7)17 
C) 7)38 
D) 7)58

Question 11

Calculate the molar solubility of thallium(I)chloride in 0.30 M NaCl at 25°C.Ksp for TlCl is
1)7 × 10-4.

Accepted Answer

A) 5)1 × 10-5 M 
B) 5)7 × 10-4 M 
C) 7)1 × 10-3 M 
D) 1)3 × 10-2 M 
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 12

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

Accepted Answer

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

Question 13

A buffer prepared by mixing 50.00 mL of 0.10 M HF with 50.00 mL of 0.10 M NaF will have a pH that is ________ 7.0.

Accepted Answer

The answer of A buffer prepared by mixing 50.00 mL...

Question 14

The following plot shows a titration curve for the titration of 1.00 L of 1.00 M diprotic acid HS1U1B12S1U1B0A with NaOH.  
-Which point a-d represents pKa1?

Accepted Answer

A) point a 
B) point b 
C) point c 
D) point d 
A) point a 
B) point b 
C) point c 
D) point d

Question 15

The equivalence point pH of the titration of four weak acids is given.Which is the strongest acid?

Accepted Answer

A) 7)24 
B) 7)86 
C) 8)12 
D) 8)43 
A) 7)24 
B) 7)86 
C) 8)12 
D) 8)43

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 Kb for the TRIS/TRISH+ is 1.2 × 10-6.

Accepted Answer

A) 5)92 
B) 6)36 
C) 7)36 
D) 7)64 
A) 5)92 
B) 6)36 
C) 7)36 
D) 7)64

Question 17

Use the graphs below to answer the following questions.  
-What is the characteristic pH-titration curve for the titration of a weak acid by a strong base?

Accepted Answer

A) A 
B) B 
C) C 
D) D 
A) A 
B) B 
C) C 
D) D

Question 18

The following pictures represent solutions at various points in the titration of a weak acid HA with aqueous KOH.Unshaded spheres represent H atoms,black spheres represent oxygen atoms,and shaded spheres represent AS1U1P1-S1S1P0 ions.(KS1U1P1+S1S1P0,HS1U1B13S1U1B0OS1U1P1+S1S1P0 initially present,OHS1U1P1-S1S1P0 initially present and solvent water molecules have been omitted for clarity).  
-Which picture represents the solution before the addition of any KOH?

Accepted Answer

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

Question 19

Use the graphs below to answer the following questions.  
-What is the characteristic pH-titrant curve for the titration of a strong base by a strong acid?

Accepted Answer

A) A 
B) B 
C) C 
D) D 
A) A 
B) B 
C) C 
D) D

Question 20

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?

Accepted Answer

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

Exam 15: Applications of Aqueous Equilibria

Which statement about buffers is true?

Which set of ions precipitate as sulfides?

Which pair of ions can be separated by the addition of chloride ion?

The dissociation equilibrium constants for the protonated form of alanine (a diprotic amino acid,H2X+)are Ka1 = 4.6 × 10-3 and Ka2 = 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?

Which is a net ionic equation for the neutralization of a weak acid with a strong base?

The following plot shows two titration curves,each representing the titration of 50.00 mL of 0.100 M acid with 0.100 M NaOH. -Which point a-d represents the equivalence point for the titration of a strong acid?

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?

What is the equation relating the equilibrium constant Kn for the neutralization of a weak acid with a weak base to the Ka of the acid,the Kb of the base and Kw?

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 Ka2 for dihydrogen phosphate is 6.2 × 10-8 and the equilibrium reaction of interest is H2PO4-(aq)+ H2O(l)⇌ H3O+(aq)+ HPO4-(aq).

Calculate the molar solubility of thallium(I)chloride in 0.30 M NaCl at 25°C.Ksp for TlCl is 1)7 × 10-4.

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

A buffer prepared by mixing 50.00 mL of 0.10 M HF with 50.00 mL of 0.10 M NaF will have a pH that is ________ 7.0.

The following plot shows a titration curve for the titration of 1.00 L of 1.00 M diprotic acid H2A with NaOH. -Which point a-d represents pKa1?

The equivalence point pH of the titration of four weak acids is given.Which is the strongest acid?

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 Kb for the TRIS/TRISH+ is 1.2 × 10-6.

Use the graphs below to answer the following questions. -What is the characteristic pH-titration curve for the titration of a weak acid by a strong base?

Use the graphs below to answer the following questions. -What is the characteristic pH-titrant curve for the titration of a strong base by a strong acid?

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?

Chemistry: Matter and Measurement

Atoms, molecules, and Ions

Formulas, equations, and Moles

Reactions in Aqueous Solutions

Periodicity and the Atomic Structure of Atoms

Ionic Bonds and Some Main-Group Chemistry

Covalent Bonds and Molecular Structure

Thermochemistry: Chemical Energy

Gases: Their Properties and Behavior

Liquids,solids,and Phase Changes

Solutions and Their Properties

Chemical Kinetics

Chemical Equilibrium

Aqueous Equilibria: Acids and Bases

Thermodynamics: Entropy, free Energy, and Equilibrium

Electrochemistry

Hydrogen, oxygen, and Water

The Main-Group Elements

Transition Elements and Coordination Chemistry

Metals and Solid-State Materials

Nuclear Chemistry

Organic and Biological Chemistry

Filters

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?

What is the equation relating the equilibrium constant K_n for the neutralization of a weak acid with a weak base to the K_a of the acid,the K_b of the base and K_w?

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).

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.

The following plot shows a titration curve for the titration of 1.00 L of 1.00 M diprotic acid H₂A with NaOH. -Which point a-d represents pK_a1?

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.

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?