Question 1

Calculate the pH of a buffered solution.

Accepted Answer

A buffer solution contains both a weak acid and its conjugate base, or a weak base and its conjugate acid, as major species in solution.

Question 2

Determine the ratio of conjugate base to acid for a buffered solution at pH = 4.3 made from propionic acid, (Ka = 1.34 x10-5).

Accepted Answer

A^-/HA = 0.267

Question 3

In which of the following titrations will the pH be less than 7 at the equivalence point?

Accepted Answer

A)  acetic acid titrated with sodium hydroxide 
B)  perchloric acid titrated with lithium hydroxide 
C)  sodium hydroxide titrated with hydrochloric acid 
D)  ammonium bromide titrated with perchloric acid 
E)  perchloric acid titrated with methyl amine 
A)  acetic acid titrated with sodium hydroxide 
B)  perchloric acid titrated with lithium hydroxide 
C)  sodium hydroxide titrated with hydrochloric acid 
D)  ammonium bromide titrated with perchloric acid 
E)  perchloric acid titrated with methyl amine E

Question 4

Which of the following will have the smallest pH change upon the addition of 0.001 mole strong acid?

Accepted Answer

A)  50 mL of a total concentration of 0.10 M pH = 5.2 acetate buffer 
B)  100 mL of a total concentration of 0.050 M pH = 5.2 acetate buffer 
C)  75 mL of a total concentration of 0.067 M pH = 5.2 acetate buffer 
D)  250 mL of a total concentration of 0.020 M pH = 5.2 acetate buffer 
E)  25 ml of total concentration of 0.20 M pH = 5.2 acetate buffer 
A)  50 mL of a total concentration of 0.10 M pH = 5.2 acetate buffer 
B)  100 mL of a total concentration of 0.050 M pH = 5.2 acetate buffer 
C)  75 mL of a total concentration of 0.067 M pH = 5.2 acetate buffer 
D)  250 mL of a total concentration of 0.020 M pH = 5.2 acetate buffer 
E)  25 ml of total concentration of 0.20 M pH = 5.2 acetate buffer

Question 5

What is the pH of a solution made by the addition of 0.34 mole of Na2HPO4 and 0.65 mole of NaH2PO4 and sufficient water to give a total volume of 1.2 L?If needed, use the following equation: pH = pKa + log(A-/HA)

Accepted Answer

Question 6

When is a solution a buffer?

Accepted Answer

When the solution pH is within

Question 7

A biochemist wishes to study the activity of an enzyme that produces one mole hydrogen ion for every mole of product produced. However, the enzyme is sensitive to changes in pH and will become inactive at pH less than 7.1. If the initial pH of the solution is 7.21 set with a phosphate buffer (the pKa's of the three acid-conjugate base pairs derived from phosphoric acid, H3PO4, are 2.12, 7.21 and 12.32) and the reaction is designed to produce 0.15 moles of product in a volume of 250 mL, what is the minimum concentration of the conjugate acid in the buffer solution?

Accepted Answer

A)  0.46 M 
B)  0.53 M 
C)  0.82 M 
D)  1.12 M 
E)  1.25 M 
A)  0.46 M 
B)  0.53 M 
C)  0.82 M 
D)  1.12 M 
E)  1.25 M

Question 8

What is the concentration of Ca2+ in a saturated solution of calcium phosphate Ca3(PO4)2 (Ksp = 2.07 x 10-33)?

Accepted Answer

Question 9

An aqueous solution is 0.2 M in both Mg2+ and Pb2+ ions. You wish to separate the two metal ions by adding oxalate, C2O42-. What is the highest possible oxalate-ion concentration such that only one of the two metal ions will form a solid?Ksp (MgC2O4) = 8.5 x 10-5 Ksp (PbC2O4) = 2.7 x 10-11

Accepted Answer

[C₂O₄^2-] can be 4.25 x10

Question 10

How would you make a buffer of pH = 3.75 from the following solutions with a total volume of 300 ml? (Ka = 1.77 x10-4 for Formic Acid, HCO2H); 0.100M HCOOH; 0.100 M HClO4; 0.100 M NaOH; 0.100 M NH3

Accepted Answer

take 200ml of HCOOH

Question 11

The equivalence point for titration of 50 ml of 0.1 M formic acid, HCO2H (a weak acid) requires what volume of 0.2 M calcium hydroxidem, Ca(OH)2?

Accepted Answer

A)  50 ml 
B)  25 ml 
C)  less than 12.5 ml as formic acid is a weak acid 
D)  12.5 ml 
E)  between 12.5 and 25 ml as formic acid is a weak acid 
A)  50 ml 
B)  25 ml 
C)  less than 12.5 ml as formic acid is a weak acid 
D)  12.5 ml 
E)  between 12.5 and 25 ml as formic acid is a weak acid

Question 12

A 5.00 mL sample containing sulphurous acid (Ka1 = 1.5 x 10-2; Ka2 = 1.0 x10-7) is titrated with 0.1324M NaOH. The stoichiometric point is at 25.32 mL. How many g of H2SO3 are present in the sample and what is the pH at the stoichiometric point?

Accepted Answer

Question 13

When 0.1 moles of HCl are added to 1 L of solution containing 0.12 moles of aqueous Na2CO3, the major species present are

Accepted Answer

A)  Na+, Cl-, H2O, HCO3-. 
B)  Na+, Cl-, H2O, CO32-. 
C)  Na+, Cl-, H2O, HCO3-, CO32-. 
D)  HCl, Na+, CO32-. 
E)  Na+, Cl-, H2O, H2CO3, CO32. 
A)  Na+, Cl-, H2O, HCO3-. 
B)  Na+, Cl-, H2O, CO32-. 
C)  Na+, Cl-, H2O, HCO3-, CO32-. 
D)  HCl, Na+, CO32-. 
E)  Na+, Cl-, H2O, H2CO3, CO32.

Question 14

When 0.1 moles of HC2H3O2 and 0.1 moles of NaC2H3O2 are added to make 1 L of aqueous solution, the major species present are

Accepted Answer

A)  Na+, H2O and HC2H3O2. 
B)  HC2H3O2 and C2H3O2-. 
C)  H2O, Na+ and C2H3O2-. 
D)  NaC2H3O2, HC2H3O2 and H2O. 
E)  Na+, H2O, HC2H3O2, C2H3O2-. 
A)  Na+, H2O and HC2H3O2. 
B)  HC2H3O2 and C2H3O2-. 
C)  H2O, Na+ and C2H3O2-. 
D)  NaC2H3O2, HC2H3O2 and H2O. 
E)  Na+, H2O, HC2H3O2, C2H3O2-.

Question 15

What is the concentration of phosphate in a solution made from a 0.22 M phosphoric acid whose pH has been adjusted to 7.1 by the addition of solid potassium hydroxide (assume no volume change)?

Accepted Answer

The answer of What is the concentration of phosphate in...

Question 16

A buffer solution made from ammonia, NH3, and ammonium chloride, NH4Cl, is prepared with pH 9.0. If Kb of NH3 is 1.78x10-5 and the total concentration of all nitrogen species is 0.25 M, what are the nitrogen concentrations?

Accepted Answer

This is a difficult question a

Question 17

In the selective precipitation of metal ions as sulphide salts, usable concentrations of the S2- ions can be maintained by bubbling H2S through a solution buffered at a pH of about 10.0. How many mL of 6 M HCl would need to be added to 3.5 mL of a solution 5.6 M in aqueous ammonia to form a solution buffered at pH 10.0?

Accepted Answer

Question 18

The following graph shows the titration of a 0.150 M benzoic acid solution. At what pH range would benzoic acid be appropriate to make a buffer?

Accepted Answer

A)  2.2 
B)  3.5 
C)  4.0 
D)  7.5 
E)  10.0 
A)  2.2 
B)  3.5 
C)  4.0 
D)  7.5 
E)  10.0

Question 19

Write the equilibrium constant expression and determine the solubility constant for HgS dissolving in a cyanide solution. (HgS, Ksp = 1.6 x 10-54) ((Hg(CN)2), Kf = 4 x 1041)

Accepted Answer

K = K_spK_f = 6

Question 20

What is the concentration of [PbCl3]- when PbCl2 solid first begins to precipitate on addition of NaCl salt to a 0.5 M PbNO3 solution?
Pb2+ + 3Cl- $\rightleftharpoons$ [PbCl3]- 
Kf = 2.4 x 101pKsp(PbCl2) = 4.77

Accepted Answer

Multi-step problem involving d

Calculate the pH of a buffered solution.

Determine the ratio of conjugate base to acid for a buffered solution at pH = 4.3 made from propionic acid, (K_a = 1.34 x10^-5).

In which of the following titrations will the pH be less than 7 at the equivalence point?

Which of the following will have the smallest pH change upon the addition of 0.001 mole strong acid?

What is the pH of a solution made by the addition of 0.34 mole of Na₂HPO₄ and 0.65 mole of NaH₂PO₄ and sufficient water to give a total volume of 1.2 L?If needed, use the following equation: pH = pK_a + log(A^-/HA)

When is a solution a buffer?

What is the concentration of Ca²⁺ in a saturated solution of calcium phosphate Ca₃(PO₄)₂ (K_sp = 2.07 x 10^-33)?

How would you make a buffer of pH = 3.75 from the following solutions with a total volume of 300 ml? (K_a = 1.77 x10^-4 for Formic Acid, HCO₂H); 0.100M HCOOH; 0.100 M HClO₄; 0.100 M NaOH; 0.100 M NH₃

The equivalence point for titration of 50 ml of 0.1 M formic acid, HCO₂H (a weak acid) requires what volume of 0.2 M calcium hydroxidem, Ca(OH)₂?

A 5.00 mL sample containing sulphurous acid (K_a1 = 1.5 x 10^-2; K_a2 = 1.0 x10^-7) is titrated with 0.1324M NaOH. The stoichiometric point is at 25.32 mL. How many g of H₂SO₃ are present in the sample and what is the pH at the stoichiometric point?

When 0.1 moles of HCl are added to 1 L of solution containing 0.12 moles of aqueous Na₂CO₃, the major species present are

When 0.1 moles of HC₂H₃O₂ and 0.1 moles of NaC₂H₃O₂ are added to make 1 L of aqueous solution, the major species present are

What is the concentration of phosphate in a solution made from a 0.22 M phosphoric acid whose pH has been adjusted to 7.1 by the addition of solid potassium hydroxide (assume no volume change)?

A buffer solution made from ammonia, NH₃, and ammonium chloride, NH₄Cl, is prepared with pH 9.0. If K_b of NH₃ is 1.78x10^-5and the total concentration of all nitrogen species is 0.25 M, what are the nitrogen concentrations?

The following graph shows the titration of a 0.150 M benzoic acid solution. At what pH range would benzoic acid be appropriate to make a buffer?

Write the equilibrium constant expression and determine the solubility constant for HgS dissolving in a cyanide solution. (HgS, K_sp= 1.6 x 10^-54) ((Hg(CN)₂), K_f = 4 x 10⁴¹)

What is the concentration of [PbCl₃]^-when PbCl₂ solid first begins to precipitate on addition of NaClsalt to a 0.5 M PbNO₃ solution? Pb²⁺ + 3Cl^- $\rightleftharpoons$ [PbCl₃]^- K_f = 2.4 x 10¹pK_sp(PbCl₂) = 4.77

Fundamental Concepts of Chemistry

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Energy and Its Conservation

Atoms and Light

Atomic Energies and Periodicity

Fundamentals of Chemical Bonding

Theories of Chemical Bonding

Effects of Intermolecular Forces

Properties of Solutions

Organic Chemistrystructure

Organic Chemistryreactions

Spontaneity of Chemical Processes

Kinetics: Mechanisms and Rates of Reactions

Principles of Chemical Equilibrium

Aqueous Acidbase Equilibria

Electron Transfer Reactions

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Exam 16: Applications of Aqueous Equilibria

Calculate the pH of a buffered solution.

Determine the ratio of conjugate base to acid for a buffered solution at pH = 4.3 made from propionic acid, (Ka = 1.34 x10-5).

In which of the following titrations will the pH be less than 7 at the equivalence point?

Which of the following will have the smallest pH change upon the addition of 0.001 mole strong acid?

What is the pH of a solution made by the addition of 0.34 mole of Na2HPO4 and 0.65 mole of NaH2PO4 and sufficient water to give a total volume of 1.2 L?If needed, use the following equation: pH = pKa + log(A-/HA)

When is a solution a buffer?

What is the concentration of Ca2+ in a saturated solution of calcium phosphate Ca3(PO4)2 (Ksp = 2.07 x 10-33)?

An aqueous solution is 0.2 M in both Mg2+ and Pb2+ ions. You wish to separate the two metal ions by adding oxalate, C2O42-. What is the highest possible oxalate-ion concentration such that only one of the two metal ions will form a solid?Ksp (MgC2O4) = 8.5 x 10-5 Ksp (PbC2O4) = 2.7 x 10-11

How would you make a buffer of pH = 3.75 from the following solutions with a total volume of 300 ml? (Ka = 1.77 x10-4 for Formic Acid, HCO2H); 0.100M HCOOH; 0.100 M HClO4; 0.100 M NaOH; 0.100 M NH3

The equivalence point for titration of 50 ml of 0.1 M formic acid, HCO2H (a weak acid) requires what volume of 0.2 M calcium hydroxidem, Ca(OH)2?

A 5.00 mL sample containing sulphurous acid (Ka1 = 1.5 x 10-2; Ka2 = 1.0 x10-7) is titrated with 0.1324M NaOH. The stoichiometric point is at 25.32 mL. How many g of H2SO3 are present in the sample and what is the pH at the stoichiometric point?

When 0.1 moles of HCl are added to 1 L of solution containing 0.12 moles of aqueous Na2CO3, the major species present are

When 0.1 moles of HC2H3O2 and 0.1 moles of NaC2H3O2 are added to make 1 L of aqueous solution, the major species present are

What is the concentration of phosphate in a solution made from a 0.22 M phosphoric acid whose pH has been adjusted to 7.1 by the addition of solid potassium hydroxide (assume no volume change)?

A buffer solution made from ammonia, NH3, and ammonium chloride, NH4Cl, is prepared with pH 9.0. If Kb of NH3 is 1.78x10-5 and the total concentration of all nitrogen species is 0.25 M, what are the nitrogen concentrations?

The following graph shows the titration of a 0.150 M benzoic acid solution. At what pH range would benzoic acid be appropriate to make a buffer?

Write the equilibrium constant expression and determine the solubility constant for HgS dissolving in a cyanide solution. (HgS, Ksp = 1.6 x 10-54) ((Hg(CN)2), Kf = 4 x 1041)

What is the concentration of [PbCl3]- when PbCl2 solid first begins to precipitate on addition of NaCl salt to a 0.5 M PbNO3 solution? Pb2+ + 3Cl- ⇌\rightleftharpoons⇌ [PbCl3]- Kf = 2.4 x 101pKsp(PbCl2) = 4.77

Fundamental Concepts of Chemistry

The Behaviour of Gases

Energy and Its Conservation

Atoms and Light

Atomic Energies and Periodicity

Fundamentals of Chemical Bonding

Theories of Chemical Bonding

Effects of Intermolecular Forces

Properties of Solutions

Organic Chemistrystructure

Organic Chemistryreactions

Spontaneity of Chemical Processes

Kinetics: Mechanisms and Rates of Reactions

Principles of Chemical Equilibrium

Aqueous Acidbase Equilibria

Electron Transfer Reactions

Macromolecules

The Transition Metals

The Main Group Elements

Nuclear Chemistry and Radiochemistry

Filters

Determine the ratio of conjugate base to acid for a buffered solution at pH = 4.3 made from propionic acid, (K_a = 1.34 x10^-5).

What is the pH of a solution made by the addition of 0.34 mole of Na₂HPO₄ and 0.65 mole of NaH₂PO₄ and sufficient water to give a total volume of 1.2 L?If needed, use the following equation: pH = pK_a + log(A^-/HA)

What is the concentration of Ca²⁺ in a saturated solution of calcium phosphate Ca₃(PO₄)₂ (K_sp = 2.07 x 10^-33)?

How would you make a buffer of pH = 3.75 from the following solutions with a total volume of 300 ml? (K_a = 1.77 x10^-4 for Formic Acid, HCO₂H); 0.100M HCOOH; 0.100 M HClO₄; 0.100 M NaOH; 0.100 M NH₃

The equivalence point for titration of 50 ml of 0.1 M formic acid, HCO₂H (a weak acid) requires what volume of 0.2 M calcium hydroxidem, Ca(OH)₂?

A 5.00 mL sample containing sulphurous acid (K_a1 = 1.5 x 10^-2; K_a2 = 1.0 x10^-7) is titrated with 0.1324M NaOH. The stoichiometric point is at 25.32 mL. How many g of H₂SO₃ are present in the sample and what is the pH at the stoichiometric point?

When 0.1 moles of HCl are added to 1 L of solution containing 0.12 moles of aqueous Na₂CO₃, the major species present are

When 0.1 moles of HC₂H₃O₂ and 0.1 moles of NaC₂H₃O₂ are added to make 1 L of aqueous solution, the major species present are

A buffer solution made from ammonia, NH₃, and ammonium chloride, NH₄Cl, is prepared with pH 9.0. If K_b of NH₃ is 1.78x10^-5and the total concentration of all nitrogen species is 0.25 M, what are the nitrogen concentrations?

Write the equilibrium constant expression and determine the solubility constant for HgS dissolving in a cyanide solution. (HgS, K_sp= 1.6 x 10^-54) ((Hg(CN)₂), K_f = 4 x 10⁴¹)

What is the concentration of [PbCl₃]^-when PbCl₂ solid first begins to precipitate on addition of NaClsalt to a 0.5 M PbNO₃ solution? Pb²⁺ + 3Cl^- $\rightleftharpoons$ [PbCl₃]^- K_f = 2.4 x 10¹pK_sp(PbCl₂) = 4.77