Question 1

What is the hydroxide-ion concentration of a 0.190 M sodium oxalate (Na2C2O4)solution? For oxalic acid (H2C2O4),Ka1 = 5.6 × 10-2 and Ka2 = 5.1 × 10-5.

Accepted Answer

A) 6.1 × 10-6 M 
B) 1.0 × 10-7 M 
C) 7.9 × 10-2 M 
D) 3.1 × 10-3 M 
E) 1.8 × 10-7 M 
A) 6.1 × 10-6 M 
B) 1.0 × 10-7 M 
C) 7.9 × 10-2 M 
D) 3.1 × 10-3 M 
E) 1.8 × 10-7 M A

Question 2

Calculate the pH of a solution that is 2.00 M HF,1.00 M NaOH,and 0.546 M NaF.(Ka = 6.8 × 10-4)

Accepted Answer

A) 3.36 
B) 2.98 
C) 3.17 
D) 2.60 
E) none of these 
A) 3.36 
B) 2.98 
C) 3.17 
D) 2.60 
E) none of these A

Question 3

What is Ka for the anilinium cation,C6H5NH3+,at 25°C? (Kb for C6H5NH2 = 4.2 × 10-10 at 25°C.)

Accepted Answer

A) 1.0 × 10-7 
B) 4.2 × 104 
C) 4.2 × 10-24 
D) 2.4 × 10-5 
E) 4.2 × 10-10 
A) 1.0 × 10-7 
B) 4.2 × 104 
C) 4.2 × 10-24 
D) 2.4 × 10-5 
E) 4.2 × 10-10 D

Question 4

What is the hydronium-ion concentration in a solution resulting from mixing 133 mL of 0.100 M HCN and 80 mL of 0.100 M KOH at 25°C? Ka for HCN = 4.9 × 10-10 at 25°C.

Accepted Answer

A) 3.5 × 10-6 M 
B) 7.0 × 10-6 M 
C) 2.7 × 10-13 M 
D) 3.2 × 10-10 M 
E) 1.0 × 10-13 M 
A) 3.5 × 10-6 M 
B) 7.0 × 10-6 M 
C) 2.7 × 10-13 M 
D) 3.2 × 10-10 M 
E) 1.0 × 10-13 M

Question 5

For a 0.10 M solution of glutaric acid,HO2C(CH2)3CO2H (Ka1 = 4.6 × 10-5,Ka2 = 3.9 × 10-6),rank the following species in order of increasing equilibrium concentration.

Accepted Answer

A) H3O+ -O2C(CH2)3COO- 2C(CH2)3COO- - 2C(CH2)3CO2H 
B) OH- -O2C(CH2)3COO- 3O+ 2C(CH2)3COO- 2C(CH2)3CO2H 
C) OH- -O2C(CH2)3COO- 2C(CH2)3COO- 3O+ 2C(CH2)3CO2H 
D) H3O+ 2C(CH2)3CO2H 2C(CH2)3COO- -O2C(CH2)3COO- - 
E) OH- -O2C(CH2)3COO- 2C(CH2)3COO- 2C(CH2)3CO2H 3O+ 
A) H3O+ -O2C(CH2)3COO- 2C(CH2)3COO- - 2C(CH2)3CO2H 
B) OH- -O2C(CH2)3COO- 3O+ 2C(CH2)3COO- 2C(CH2)3CO2H 
C) OH- -O2C(CH2)3COO- 2C(CH2)3COO- 3O+ 2C(CH2)3CO2H 
D) H3O+ 2C(CH2)3CO2H 2C(CH2)3COO- -O2C(CH2)3COO- - 
E) OH- -O2C(CH2)3COO- 2C(CH2)3COO- 2C(CH2)3CO2H 3O+

Question 6

Which of the following salts is most likely to form an aqueous solution having the pH shown in the figure below?

Accepted Answer

A) NH4Cl 
B) NaBr 
C) K2CO3 
D) RbCN 
E) LiNO3 
A) NH4Cl 
B) NaBr 
C) K2CO3 
D) RbCN 
E) LiNO3

Question 7

Saccharin is a weak organic base with a Kb of 4.80 × 10-3.A 0.297-g sample of saccharin dissolved in 25.0 mL of water has a pH of 12.190.What is the molar mass of saccharin?

Accepted Answer

A) 0.823 g/mol 
B) 33.700 g/mol 
C) 6.824090785E+24 g/mol 
D) 185 g/mol 
E) 278 g/mol 
A) 0.823 g/mol 
B) 33.700 g/mol 
C) 6.824090785E+24 g/mol 
D) 185 g/mol 
E) 278 g/mol

Question 8

Which of the following solutions will not yield an effective NaH2PO4/Na2HPO4 buffer?

Accepted Answer

A) 2.0 M NaH2PO4 + 1.0 M NaOH 
B) 1.0 M NaH2PO4 + 1.0 M Na2HPO4 
C) 1.0 M H3PO4 + 1.0 M Na3PO4 
D) 2.0 M Na2HPO4 + 1.0 M HCl 
E) 1.0 M H3PO4 + 1.0 M NaH2PO4 
A) 2.0 M NaH2PO4 + 1.0 M NaOH 
B) 1.0 M NaH2PO4 + 1.0 M Na2HPO4 
C) 1.0 M H3PO4 + 1.0 M Na3PO4 
D) 2.0 M Na2HPO4 + 1.0 M HCl 
E) 1.0 M H3PO4 + 1.0 M NaH2PO4

Question 9

Which acid-base combination is depicted by this titration curve?

Accepted Answer

A) Titration of a weak base with a strong acid. 
B) Titration of a weak acid with a strong base. 
C) Titration of a strong acid with a strong base. 
D) Titration of a strong base with a strong acid. 
E) Not enough information provided. 
A) Titration of a weak base with a strong acid. 
B) Titration of a weak acid with a strong base. 
C) Titration of a strong acid with a strong base. 
D) Titration of a strong base with a strong acid. 
E) Not enough information provided.

Question 10

What will happen if a small amount of sodium hydroxide is added to a 0.1 M solution of ammonia?

Accepted Answer

A) Kb for ammonia will decrease. 
B) The percent ionization of ammonia will increase. 
C) Kb for ammonia will increase. 
D) The percent ionization of ammonia will decrease. 
E) The percent ionization of ammonia will remain unchanged. 
A) Kb for ammonia will decrease. 
B) The percent ionization of ammonia will increase. 
C) Kb for ammonia will increase. 
D) The percent ionization of ammonia will decrease. 
E) The percent ionization of ammonia will remain unchanged.

Question 11

Suppose a buffer solution is made from formic acid (HCHO2)and sodium formate (NaCHO2).What is the net ionic equation for the reaction that occurs when a small amount of hydrochloric acid is added to the buffer?

Accepted Answer

A) H3O+(aq)+ HCHO2(aq)→ H2O(l)+ H2CHO2+(aq) 
B) H3O+(aq)+ CHO2-(aq)→ HCHO2(aq)+ H2O(l) 
C) HCl(aq)+ CHO2-(aq)→ HCHO2(aq)+ Cl-(aq) 
D) HCl(aq)+ OH-(aq)→ H2O(l)+ Cl-(aq) 
E) H3O+(aq)+ OH-(aq)→ 2H2O(l) 
A) H3O+(aq)+ HCHO2(aq)→ H2O(l)+ H2CHO2+(aq) 
B) H3O+(aq)+ CHO2-(aq)→ HCHO2(aq)+ H2O(l) 
C) HCl(aq)+ CHO2-(aq)→ HCHO2(aq)+ Cl-(aq) 
D) HCl(aq)+ OH-(aq)→ H2O(l)+ Cl-(aq) 
E) H3O+(aq)+ OH-(aq)→ 2H2O(l)

Question 12

Which of the following solutions would show the greatest change in pH upon the addition of 10.0 mL of 1.0 M NaOH to 1.0 L of the solution?

Accepted Answer

A) 0.50 M HC2H3O2 
B) 0.50 M HC2H3O2 + 0.50 M NaC2H3O2 
C) 0.10 M HC2H3O2 + 0.10 M NaC2H3O2 
D) 0.10 M HC2H3O2 
E) 0.50 M NaC2H3O2 
A) 0.50 M HC2H3O2 
B) 0.50 M HC2H3O2 + 0.50 M NaC2H3O2 
C) 0.10 M HC2H3O2 + 0.10 M NaC2H3O2 
D) 0.10 M HC2H3O2 
E) 0.50 M NaC2H3O2

Question 13

What is the pH of a 0.35 M solution of methylamine (CH3NH2,Kb = 4.4 × 10-4)at 25oC?

Accepted Answer

A) 5.55 
B) 0.46 
C) 12.09 
D) 13.54 
E) 1.91 
A) 5.55 
B) 0.46 
C) 12.09 
D) 13.54 
E) 1.91

Question 14

Which of the following salts is most likely to form an aqueous solution having the pH shown in the figure below?

Accepted Answer

A) Na2CO3 
B) RbF 
C) NH4Cl 
D) Zn(NO3)2 
E) KCl 
A) Na2CO3 
B) RbF 
C) NH4Cl 
D) Zn(NO3)2 
E) KCl

Question 15

What is the concentration of C2O42- in a 0.370 M oxalic acid,H2C2O4,solution? For oxalic acid,Ka1 = 5.6 × 10-2 and Ka2 = 5.1 × 10-5.

Accepted Answer

A) 1.2 × 10-1 M 
B) -3 × 10-3 M 
C) 4.3 × 10-3 M 
D) 5.1 × 10-5 M 
E) 1.4 × 10-1 M 
A) 1.2 × 10-1 M 
B) -3 × 10-3 M 
C) 4.3 × 10-3 M 
D) 5.1 × 10-5 M 
E) 1.4 × 10-1 M

Question 16

For a solution equimolar in HCN and NaCN,which statement is false?

Accepted Answer

A) [H+] is equal to Ka. 
B) [H+] is larger than it would be if only the HCN were in solution. 
C) Addition of NaOH will increase [CN-] and decrease [HCN]. 
D) Addition of more NaCN will shift the acid-dissociation equilibrium of HCN to the left. 
E) Addition of more HCN will shift the acid-dissociation equilibrium of HCN to the right. 
A) [H+] is equal to Ka. 
B) [H+] is larger than it would be if only the HCN were in solution. 
C) Addition of NaOH will increase [CN-] and decrease [HCN]. 
D) Addition of more NaCN will shift the acid-dissociation equilibrium of HCN to the left. 
E) Addition of more HCN will shift the acid-dissociation equilibrium of HCN to the right.

Question 17

Which of the following is the most effective buffer system for a pH value of 4.45?

Accepted Answer

A) H2CO3/HCO3-  (Ka1 for H2CO3 is 4.3 × 10-7) 
B) HCO3-/CO32-  (Ka2 for H2CO3 is 4.8 × 10-11) 
C) H2S/HS-  (Ka1 for H2S is 8.9 × 10-8) 
D) HC2O4-/C2O42-  (Ka2 for H2C2O4 is 5.1 × 10-5) 
E) H3PO4/H2PO4-  (Ka1 for H3PO4 is 6.9 × 10-3) 
A) H2CO3/HCO3-  (Ka1 for H2CO3 is 4.3 × 10-7) 
B) HCO3-/CO32-  (Ka2 for H2CO3 is 4.8 × 10-11) 
C) H2S/HS-  (Ka1 for H2S is 8.9 × 10-8) 
D) HC2O4-/C2O42-  (Ka2 for H2C2O4 is 5.1 × 10-5) 
E) H3PO4/H2PO4-  (Ka1 for H3PO4 is 6.9 × 10-3)

Question 18

What is the hydronium-ion concentration at equilibrium in a 0.10 M solution of aniline (C6H5NH2,Kb = 4.2 × 10-10)at 25oC?

Accepted Answer

A) 1.0 × 10-13 M 
B) 1.0 × 10-1 M 
C) 1.5 × 10-9 M 
D) 6.5 × 10-6 M 
E) 6.5 × 10-5 M 
A) 1.0 × 10-13 M 
B) 1.0 × 10-1 M 
C) 1.5 × 10-9 M 
D) 6.5 × 10-6 M 
E) 6.5 × 10-5 M

Question 19

In a 0.01 M solution of 1,4-butanedicarboxylic acid,HOOCCH2CH2COOH (Ka1 = 2.9 × 10-5,Ka2 = 5.3 × 10-6),which species is present in the lowest concentration?

Accepted Answer

A) (-OOCCH2CH2COO-)(aq) 
B) H2O 
C) HOOCCH2CH2COO-(aq) 
D) H3O+(aq) 
E) HOOCCH2CH2COOH(aq) 
A) (-OOCCH2CH2COO-)(aq) 
B) H2O 
C) HOOCCH2CH2COO-(aq) 
D) H3O+(aq) 
E) HOOCCH2CH2COOH(aq)

Question 20

What is the pH of an initially 0.428 M solution of a weak monoprotic acid that is 0.11 % ionized when equilibrium is established? (assume Ca/Ka ≥102)

Accepted Answer

A) 3.32 
B) 7.00 
C) 1.32 
D) 10.63 
E) 10.68 
A) 3.32 
B) 7.00 
C) 1.32 
D) 10.63 
E) 10.68

Exam 16: Acid-Base Equilibria

What is the hydroxide-ion concentration of a 0.190 M sodium oxalate (Na2C2O4)solution? For oxalic acid (H2C2O4),Ka1 = 5.6 × 10-2 and Ka2 = 5.1 × 10-5.

Calculate the pH of a solution that is 2.00 M HF,1.00 M NaOH,and 0.546 M NaF.(Ka = 6.8 × 10-4)

What is Ka for the anilinium cation,C6H5NH3+,at 25°C? (Kb for C6H5NH2 = 4.2 × 10-10 at 25°C.)

What is the hydronium-ion concentration in a solution resulting from mixing 133 mL of 0.100 M HCN and 80 mL of 0.100 M KOH at 25°C? Ka for HCN = 4.9 × 10-10 at 25°C.

For a 0.10 M solution of glutaric acid,HO2C(CH2)3CO2H (Ka1 = 4.6 × 10-5,Ka2 = 3.9 × 10-6),rank the following species in order of increasing equilibrium concentration.

Which of the following salts is most likely to form an aqueous solution having the pH shown in the figure below?

Saccharin is a weak organic base with a Kb of 4.80 × 10-3.A 0.297-g sample of saccharin dissolved in 25.0 mL of water has a pH of 12.190.What is the molar mass of saccharin?

Which of the following solutions will not yield an effective NaH2PO4/Na2HPO4 buffer?

Which acid-base combination is depicted by this titration curve?

What will happen if a small amount of sodium hydroxide is added to a 0.1 M solution of ammonia?

Suppose a buffer solution is made from formic acid (HCHO2)and sodium formate (NaCHO2).What is the net ionic equation for the reaction that occurs when a small amount of hydrochloric acid is added to the buffer?

Which of the following solutions would show the greatest change in pH upon the addition of 10.0 mL of 1.0 M NaOH to 1.0 L of the solution?

What is the pH of a 0.35 M solution of methylamine (CH3NH2,Kb = 4.4 × 10-4)at 25oC?

Which of the following salts is most likely to form an aqueous solution having the pH shown in the figure below?

What is the concentration of C2O42- in a 0.370 M oxalic acid,H2C2O4,solution? For oxalic acid,Ka1 = 5.6 × 10-2 and Ka2 = 5.1 × 10-5.

For a solution equimolar in HCN and NaCN,which statement is false?

Which of the following is the most effective buffer system for a pH value of 4.45?

What is the hydronium-ion concentration at equilibrium in a 0.10 M solution of aniline (C6H5NH2,Kb = 4.2 × 10-10)at 25oC?

In a 0.01 M solution of 1,4-butanedicarboxylic acid,HOOCCH2CH2COOH (Ka1 = 2.9 × 10-5,Ka2 = 5.3 × 10-6),which species is present in the lowest concentration?

What is the pH of an initially 0.428 M solution of a weak monoprotic acid that is 0.11 % ionized when equilibrium is established? (assume Ca/Ka ≥102)

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What is the hydroxide-ion concentration of a 0.190 M sodium oxalate (Na₂C₂O₄)solution? For oxalic acid (H₂C₂O₄),Ka₁ = 5.6 × 10^-2 and Ka₂ = 5.1 × 10^-5.

Calculate the pH of a solution that is 2.00 M HF,1.00 M NaOH,and 0.546 M NaF.(K_a = 6.8 × 10^-4)

What is K_a for the anilinium cation,C₆H₅NH₃⁺,at 25°C? (K_b for C₆H₅NH₂ = 4.2 × 10^-10 at 25°C.)

What is the hydronium-ion concentration in a solution resulting from mixing 133 mL of 0.100 M HCN and 80 mL of 0.100 M KOH at 25°C? K_a for HCN = 4.9 × 10^-10 at 25°C.

For a 0.10 M solution of glutaric acid,HO₂C(CH₂)₃CO₂H (Ka₁ = 4.6 × 10^-5,Ka₂ = 3.9 × 10^-6),rank the following species in order of increasing equilibrium concentration.

Saccharin is a weak organic base with a K_b of 4.80 × 10^-3.A 0.297-g sample of saccharin dissolved in 25.0 mL of water has a pH of 12.190.What is the molar mass of saccharin?

Which of the following solutions will not yield an effective NaH₂PO₄/Na₂HPO₄ buffer?

Suppose a buffer solution is made from formic acid (HCHO₂)and sodium formate (NaCHO₂).What is the net ionic equation for the reaction that occurs when a small amount of hydrochloric acid is added to the buffer?

What is the pH of a 0.35 M solution of methylamine (CH₃NH₂,K_b = 4.4 × 10^-4)at 25^oC?

What is the concentration of C₂O₄^2- in a 0.370 M oxalic acid,H₂C₂O₄,solution? For oxalic acid,Ka₁ = 5.6 × 10^-2 and Ka₂ = 5.1 × 10^-5.

What is the hydronium-ion concentration at equilibrium in a 0.10 M solution of aniline (C₆H₅NH₂,K_b = 4.2 × 10^-10)at 25^oC?

In a 0.01 M solution of 1,4-butanedicarboxylic acid,HOOCCH₂CH₂COOH (Ka₁ = 2.9 × 10^-5,Ka₂ = 5.3 × 10^-6),which species is present in the lowest concentration?

What is the pH of an initially 0.428 M solution of a weak monoprotic acid that is 0.11 % ionized when equilibrium is established? (assume C_a/K_a ≥10²)