Question 1

A lab technician adds 0.015 mol of KOH to 1.00 L of 0.0010 M Ca(NO3)2. Ksp = 6.5 *10¯6 for Ca(OH)2. Which of the following statements is correct?

Accepted Answer

A)  Calcium hydroxide precipitates until the solution is saturated. 
B)  The solution is unsaturated and no precipitate forms. 
C)  The concentration of calcium ions is reduced by the addition of the hydroxide ions. 
D)  One must know Ksp for calcium nitrate to make meaningful predictions on this system. 
E)  The presence of KOH will raise the solubility of Ca(NO3)2. 
A)  Calcium hydroxide precipitates until the solution is saturated. 
B)  The solution is unsaturated and no precipitate forms. 
C)  The concentration of calcium ions is reduced by the addition of the hydroxide ions. 
D)  One must know Ksp for calcium nitrate to make meaningful predictions on this system. 
E)  The presence of KOH will raise the solubility of Ca(NO3)2.

Question 2

Calculate the solubility of lead(II) iodide, PbI2, in 0.025 M KI. Ksp = 7.9 *10¯9

Accepted Answer

A)  4.5 *10¯2 M 
B)  2.8 * 10¯2 M 
C)  8.9 * 10¯5 M 
D)  5.0 * 10¯5 M 
E)  1.3 * 10¯5 M 
A)  4.5 *10¯2 M 
B)  2.8 * 10¯2 M 
C)  8.9 * 10¯5 M 
D)  5.0 * 10¯5 M 
E)  1.3 * 10¯5 M

Question 3

When a weak acid is titrated with a weak base, the pH at the equivalence point

Accepted Answer

A)  is greater than 7.0. 
B)  is equal to 7.0. 
C)  is less than 7.0. 
D)  is determined by the sizes of Ka and Kb. 
E)  is no longer affected by addition of base. 
A)  is greater than 7.0. 
B)  is equal to 7.0. 
C)  is less than 7.0. 
D)  is determined by the sizes of Ka and Kb. 
E)  is no longer affected by addition of base.

Question 4

A 20.0-mL sample of 0.25 M HNO3 is titrated with 0.15 M NaOH. What is the pH of the solution after 30.0 mL of NaOH have been added to the acid?

Accepted Answer

A)  2.00 
B)  1.60 
C)  1.05 
D)  1.00 
E)  None of these choices is correct. 
A)  2.00 
B)  1.60 
C)  1.05 
D)  1.00 
E)  None of these choices is correct.

Question 5

Buffer solutions with the component concentrations shown below were prepared. Which of them should have the highest pH?

Accepted Answer

A)  [H2PO4¯] = 0.50 M, [HPO42¯] = 0.50 M 
B)  [H2PO4¯] = 1.0 M, [HPO42¯] = 1.0 M 
C)  [H2PO4¯] = 1.0 M, [HPO42¯] = 0.50 M 
D)  [H2PO4¯] = 0.50 M, [HPO42¯] = 1.0 M 
E)  [H2PO4¯] = 0.75 M, [HPO42¯] = 1.0 M 
A)  [H2PO4¯] = 0.50 M, [HPO42¯] = 0.50 M 
B)  [H2PO4¯] = 1.0 M, [HPO42¯] = 1.0 M 
C)  [H2PO4¯] = 1.0 M, [HPO42¯] = 0.50 M 
D)  [H2PO4¯] = 0.50 M, [HPO42¯] = 1.0 M 
E)  [H2PO4¯] = 0.75 M, [HPO42¯] = 1.0 M

Question 6

A diprotic acid H2A has Ka1 = 1 *10¯4 and Ka2 = 1 * 10¯8. The corresponding base A2¯ is titrated with aqueous HCl, both solutions being 0.1 mol L¯1. Which one of the following diagrams best represents the titration curve which will be seen?

Accepted Answer

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

Question 7

A buffer is prepared by adding 1.00 L of 1.0 M HCl to 750 mL of 1.5 M NaHCOO. What is the pH of this buffer? Ka = 1.7 * 10¯4

Accepted Answer

A)  2.87 
B)  3.72 
C)  3.82 
D)  3.95 
E)  4.66 
A)  2.87 
B)  3.72 
C)  3.82 
D)  3.95 
E)  4.66

Question 8

The lab technician Anna Lytic adds 2.20 mol KOH to 1.00 L of 0.5 M Al(NO3)3. What is the concentration of aluminum ions after the aluminum nitrate has reacted with the potassium hydroxide? Kf = 3.0 * 1033 for Al(OH)4¯

Accepted Answer

A)  1.8 * 10¯7 M 
B)  9.l * 10¯18 M 
C)  1.0 * 10¯31 M 
D)  3.3 * 10¯34 M 
E)  7.l *10¯36 M 
A)  1.8 * 10¯7 M 
B)  9.l * 10¯18 M 
C)  1.0 * 10¯31 M 
D)  3.3 * 10¯34 M 
E)  7.l *10¯36 M

Question 9

What is the maximum mass of KCl that can be added to 1.0 L of a 0.010 M lead(II) chloride solution without causing any precipitation of lead(II) chloride? Assume that addition of KCl does not affect the solution volume. For lead(II) chloride, Ksp = 1.6 * 10¯5

Accepted Answer

A)  3.0 g 
B)  1.5 g 
C)  0.8 g 
D)  0.8 g. 
E)  0.2 g 
A)  3.0 g 
B)  1.5 g 
C)  0.8 g 
D)  0.8 g. 
E)  0.2 g

Question 10

A buffer is prepared by adding 150 mL of 1.0 M NaOH to 250 mL of 1.0 M NaH2PO4. How many moles of HCl must be added to this buffer solution to change the pH by 0.18 units? If necessary, assume the total volume remains unchanged at 400 mL.

Accepted Answer

A)  0.025 mol HCl 
B)  0.063 mol HCl 
C)  0.082 mol HCl 
D)  0.50 mol HCl 
E)  1.0 mol HCl 
A)  0.025 mol HCl 
B)  0.063 mol HCl 
C)  0.082 mol HCl 
D)  0.50 mol HCl 
E)  1.0 mol HCl

Question 11

An acetic acid buffer containing 0.50 M CH3COOH and 0.50 M CH3COONa has a pH of 4.74. What will the pH be after 0.0020 mol of HCl has been added to 100.0 mL of the buffer?

Accepted Answer

A)  4.77 
B)  4.71 
C)  4.68 
D)  4.62 
E)  None of these choices is correct. 
A)  4.77 
B)  4.71 
C)  4.68 
D)  4.62 
E)  None of these choices is correct.

Question 12

The indicator propyl red has Ka = 3.3 * 10¯6. What would be the approximate pH range over which it would change color?

Accepted Answer

A)  3.5 to 5.5 
B)  4.5 to 6.5 
C)  5.5 to 7.5 
D)  6.5 to 8.5 
E)  None of these choices is correct. 
A)  3.5 to 5.5 
B)  4.5 to 6.5 
C)  5.5 to 7.5 
D)  6.5 to 8.5 
E)  None of these choices is correct.

Question 13

Consider the dissolution of MnS in water (Ksp = 3.0 * 10¯14).   How is the solubility of manganese(II) sulfide affected by the addition of aqueous potassium hydroxide to the system?

Accepted Answer

A)  The solubility will be unchanged. 
B)  The solubility will decrease. 
C)  The solubility will increase. 
D)  The amount of KOH added must be known before its effect can be predicted. 
E)  The pKa of H2S is needed before a reliable prediction can be made. 
A)  The solubility will be unchanged. 
B)  The solubility will decrease. 
C)  The solubility will increase. 
D)  The amount of KOH added must be known before its effect can be predicted. 
E)  The pKa of H2S is needed before a reliable prediction can be made.

Question 14

The salts X(NO3)2 and Y(NO3)2 (where X+ and Y+ are metal ions) are dissolved in water to give a solution which is 0.1 M in each of them. Which of the answers gives the concentration of chloride ions will precipitate the most YCl2 without precipitating any XCl2? Given Ksp values: XCl2, 2 * 10¯5; YCl2, 1 *10¯10

Accepted Answer

A)  1 M Cl¯ 
B)  0.1 M Cl¯ 
C)  0.01 M Cl¯ 
D)  0.001 M Cl¯ 
E)  0.0001 M Cl¯ 
A)  1 M Cl¯ 
B)  0.1 M Cl¯ 
C)  0.01 M Cl¯ 
D)  0.001 M Cl¯ 
E)  0.0001 M Cl¯

Question 15

A CH3COOH/CH3COO¯ buffer can be produced by adding a strong acid to a solution of CH3COO¯ ions.

Accepted Answer

A) True 
 B)False

Question 16

A 20.0-mL sample of 0.50 M H2C6H6O6 (ascorbic acid, a diprotic acid) was titrated with 0.50 M NaOH. The following data were gathered during the titration.   What is Ka2 for ascorbic acid?

Accepted Answer

A)  6.8 *10¯5 
B)  6.2 * 10¯6 
C)  6.2 * 10¯7 
D)  6.2 * 10¯8 
E)  2.8 * 10¯12 
A)  6.8 *10¯5 
B)  6.2 * 10¯6 
C)  6.2 * 10¯7 
D)  6.2 * 10¯8 
E)  2.8 * 10¯12

Question 17

The solubility of salt MX (solubility product constant Ksp) in water will always be greater than that of salt MX3 (solubility product constant K'sp) provided that Ksp > K'sp.

Accepted Answer

A) True 
 B)False

Question 18

A solution is prepared by adding 100 mL of 0.2 M hydrochloric acid to 100 mL of 0.4 M sodium formate. Is this a buffer solution, and if so, what is its pH?

Accepted Answer

A)  It is a buffer, pH > pKa of formic acid. 
B)  It is a buffer, pH a of formic acid. 
C)  It is a buffer, pH = pKa of formic acid. 
D)  It is a buffer, pH = pKb of sodium formate. 
E)  Since hydrochloric acid is a strong acid, this is not a buffer. 
A)  It is a buffer, pH > pKa of formic acid. 
B)  It is a buffer, pH a of formic acid. 
C)  It is a buffer, pH = pKa of formic acid. 
D)  It is a buffer, pH = pKb of sodium formate. 
E)  Since hydrochloric acid is a strong acid, this is not a buffer.

Question 19

A saturated solution of calcium hydroxide, Ca(OH)2, is in contact with excess solid Ca(OH)2. Which of the following statements correctly describes what will happen when aqueous HCl (a strong acid) is added to this mixture, and system returns to equilibrium? (For Ca(OH)2, Ksp = 6.5 * 10¯6)

Accepted Answer

A)  The solubility of Ca(OH)2 will be unchanged. 
B)  The OH¯ concentration will decrease and the Ca2+ concentration will increase. 
C)  The OH¯ concentration will increase and the Ca2+ concentration will decrease. 
D)  The concentrations of both Ca2+ and OH¯ will increase. 
E)  The solubility of Ca(OH)2 will decrease. 
A)  The solubility of Ca(OH)2 will be unchanged. 
B)  The OH¯ concentration will decrease and the Ca2+ concentration will increase. 
C)  The OH¯ concentration will increase and the Ca2+ concentration will decrease. 
D)  The concentrations of both Ca2+ and OH¯ will increase. 
E)  The solubility of Ca(OH)2 will decrease.

Question 20

Which one of the following aqueous solutions, when mixed with an equal volume of 0.10 mol L¯1 aqueous NH3, will produce a buffer solution?

Accepted Answer

A)  0.10 mol L¯1 HCl 
B)  0.20 mol L¯1 HCl 
C)  0.10 mol L¯1 CH3COOH 
D)  0.050 mol L¯1 NaOH 
E)  0.20 mol L¯1 NH4Cl 
A)  0.10 mol L¯1 HCl 
B)  0.20 mol L¯1 HCl 
C)  0.10 mol L¯1 CH3COOH 
D)  0.050 mol L¯1 NaOH 
E)  0.20 mol L¯1 NH4Cl

Exam 19: Ionic Equilibria in Aqueous Systems

A lab technician adds 0.015 mol of KOH to 1.00 L of 0.0010 M Ca(NO3)2. Ksp = 6.5 *10¯6 for Ca(OH)2. Which of the following statements is correct?

Calculate the solubility of lead(II) iodide, PbI2, in 0.025 M KI. Ksp = 7.9 *10¯9

When a weak acid is titrated with a weak base, the pH at the equivalence point

A 20.0-mL sample of 0.25 M HNO3 is titrated with 0.15 M NaOH. What is the pH of the solution after 30.0 mL of NaOH have been added to the acid?

Buffer solutions with the component concentrations shown below were prepared. Which of them should have the highest pH?

A diprotic acid H2A has Ka1 = 1 *10¯4 and Ka2 = 1 * 10¯8. The corresponding base A2¯ is titrated with aqueous HCl, both solutions being 0.1 mol L¯1. Which one of the following diagrams best represents the titration curve which will be seen?

A buffer is prepared by adding 1.00 L of 1.0 M HCl to 750 mL of 1.5 M NaHCOO. What is the pH of this buffer? Ka = 1.7 * 10¯4

The lab technician Anna Lytic adds 2.20 mol KOH to 1.00 L of 0.5 M Al(NO3)3. What is the concentration of aluminum ions after the aluminum nitrate has reacted with the potassium hydroxide? Kf = 3.0 * 1033 for Al(OH)4¯

What is the maximum mass of KCl that can be added to 1.0 L of a 0.010 M lead(II) chloride solution without causing any precipitation of lead(II) chloride? Assume that addition of KCl does not affect the solution volume. For lead(II) chloride, Ksp = 1.6 * 10¯5

A buffer is prepared by adding 150 mL of 1.0 M NaOH to 250 mL of 1.0 M NaH2PO4. How many moles of HCl must be added to this buffer solution to change the pH by 0.18 units? If necessary, assume the total volume remains unchanged at 400 mL.

An acetic acid buffer containing 0.50 M CH3COOH and 0.50 M CH3COONa has a pH of 4.74. What will the pH be after 0.0020 mol of HCl has been added to 100.0 mL of the buffer?

The indicator propyl red has Ka = 3.3 * 10¯6. What would be the approximate pH range over which it would change color?

Consider the dissolution of MnS in water (Ksp = 3.0 * 10¯14). How is the solubility of manganese(II) sulfide affected by the addition of aqueous potassium hydroxide to the system?

A CH3COOH/CH3COO¯ buffer can be produced by adding a strong acid to a solution of CH3COO¯ ions.

A 20.0-mL sample of 0.50 M H2C6H6O6 (ascorbic acid, a diprotic acid) was titrated with 0.50 M NaOH. The following data were gathered during the titration. What is Ka2 for ascorbic acid?

The solubility of salt MX (solubility product constant Ksp) in water will always be greater than that of salt MX3 (solubility product constant K'sp) provided that Ksp > K'sp.

A solution is prepared by adding 100 mL of 0.2 M hydrochloric acid to 100 mL of 0.4 M sodium formate. Is this a buffer solution, and if so, what is its pH?

A saturated solution of calcium hydroxide, Ca(OH)2, is in contact with excess solid Ca(OH)2. Which of the following statements correctly describes what will happen when aqueous HCl (a strong acid) is added to this mixture, and system returns to equilibrium? (For Ca(OH)2, Ksp = 6.5 * 10¯6)

Which one of the following aqueous solutions, when mixed with an equal volume of 0.10 mol L¯1 aqueous NH3, will produce a buffer solution?

Keys to the Study of Chemistry

The Components of Matter

Stoichiometry of Formulas and Equations

Three Major Classes of Chemical Reactions

Gases and the Kinetic-Molecular Theory

Thermochemistry: Energy Flow and Chemical Change

Quantum Theory and Atomic Structure

Electron Configuration and Chemical Periodicity

Models of Chemical Bonding

The Shapes of Molecules

Theories of Covalent Bonding

Intermolecular Forces: Liquids, Solids, and Phase Changes

The Properties of Mixtures: Solutions and Colloids

Periodic Patterns in the Main-Group Elements

Organic Compounds and the Atomic Properties of Carbon

Kinetics: Rates and Mechanisms of Chemical Reactions

Equilibrium: the Extent of Chemical Reactions

Acid-Base Equilibria

Thermodynamics: Entropy, Free Energy, and the Direction of Chemical Reactions

Electrochemistry: Chemical Change and Electrical Work

The Elements in Nature and Industry

The Transition Elements and Their Coordination Compounds

Nuclear Reactions and Their Applications

Filters

A lab technician adds 0.015 mol of KOH to 1.00 L of 0.0010 M Ca(NO₃)₂. K_sp = 6.5 *10¯⁶ for Ca(OH)₂. Which of the following statements is correct?

Calculate the solubility of lead(II) iodide, PbI₂, in 0.025 M KI. K_sp = 7.9 *10¯⁹

A 20.0-mL sample of 0.25 M HNO₃ is titrated with 0.15 M NaOH. What is the pH of the solution after 30.0 mL of NaOH have been added to the acid?

A diprotic acid H₂A has K_a1 = 1 10¯⁴ and K_a2 = 1 10¯⁸. The corresponding base A²¯ is titrated with aqueous HCl, both solutions being 0.1 mol L¯¹. Which one of the following diagrams best represents the titration curve which will be seen?

A buffer is prepared by adding 1.00 L of 1.0 M HCl to 750 mL of 1.5 M NaHCOO. What is the pH of this buffer? K_a = 1.7 * 10¯⁴

The lab technician Anna Lytic adds 2.20 mol KOH to 1.00 L of 0.5 M Al(NO₃)₃. What is the concentration of aluminum ions after the aluminum nitrate has reacted with the potassium hydroxide? K_f = 3.0 * 10³³ for Al(OH)₄¯

What is the maximum mass of KCl that can be added to 1.0 L of a 0.010 M lead(II) chloride solution without causing any precipitation of lead(II) chloride? Assume that addition of KCl does not affect the solution volume. For lead(II) chloride, K_sp = 1.6 * 10¯⁵

A buffer is prepared by adding 150 mL of 1.0 M NaOH to 250 mL of 1.0 M NaH₂PO₄. How many moles of HCl must be added to this buffer solution to change the pH by 0.18 units? If necessary, assume the total volume remains unchanged at 400 mL.

An acetic acid buffer containing 0.50 M CH₃COOH and 0.50 M CH₃COONa has a pH of 4.74. What will the pH be after 0.0020 mol of HCl has been added to 100.0 mL of the buffer?

The indicator propyl red has K_a = 3.3 * 10¯⁶. What would be the approximate pH range over which it would change color?

Consider the dissolution of MnS in water (K_sp = 3.0 * 10¯¹⁴). How is the solubility of manganese(II) sulfide affected by the addition of aqueous potassium hydroxide to the system?

A CH₃COOH/CH₃COO¯ buffer can be produced by adding a strong acid to a solution of CH₃COO¯ ions.

A 20.0-mL sample of 0.50 M H₂C₆H₆O₆ (ascorbic acid, a diprotic acid) was titrated with 0.50 M NaOH. The following data were gathered during the titration. What is K_a2 for ascorbic acid?

The solubility of salt MX (solubility product constant K_sp) in water will always be greater than that of salt MX₃ (solubility product constant K'_sp) provided that K_sp > K'_sp.

A saturated solution of calcium hydroxide, Ca(OH)₂, is in contact with excess solid Ca(OH)₂. Which of the following statements correctly describes what will happen when aqueous HCl (a strong acid) is added to this mixture, and system returns to equilibrium? (For Ca(OH)₂, K_sp = 6.5 * 10¯⁶)

Which one of the following aqueous solutions, when mixed with an equal volume of 0.10 mol L¯¹ aqueous NH₃, will produce a buffer solution?