CHM 4220 Exam 4 Study Guide Q&A Fall 2025
If a buffer solution is 0.150 M in a weak acid (Ka = 2.3 × 10-5) and 0.560 M in its conjugate
base, what is the pH? - (answers)5.20
How could you make a buffer? (Select all that apply)
-Partially neutralize a weak acid solution by addition of a strong base.
-Partially neutralize a strong acid solution by addition of a strong base.
-Partially neutralize a strong base solution by addition of a strong acid.
-Partially neutralize a weak base solution by addition of a strong acid.
-Add appropriate quantities of weak acid and its conjugate base to water. - (answers)-Partially
neutralize a weak acid solution by addition of a strong base.
-Partially neutralize a weak base solution by addition of a strong acid.
-Add appropriate quantities of weak acid and its conjugate base to water.
a) Calculate the change in pH眼睛”主题的中文文章？
when 8.00 mL of 0.100 M HCl(aq) is added to 100.0 mL of a
buffer solution that is 0.100 M in NH3(aq) and 0.100 M in NH4Cl(aq). A list of ionization
constants can be found here.
b) Calculate the change in pH when 8.00 mL of 0.100 M NaOH(aq) is added to the original
buffer solution. - (answers)a) -0.07
b) 0.07
Which pair of compounds will form a buffer in aqueous solution?
NaCN and NaOH
NaCN and KCN
HCl and NaCl
HCl and NaOH
, HCN and HCl
HCN and NaCN - (answers)HCN and NaCN
Which of the following are valid ways to make an ammonia/ammonium buffer for use in the
laboratory?
-Mix equal volumes of 1 M NH3 and 1 M NH4 .
-Mix equal volumes of 1 M NH3 and 0.01 M NH4
-Mix equal volumes of 1 M NH3 and 1 M HCl.
-Mix some volume of 1 M NH3 with half as much 1 M HCl. - (answers)-Mix some volume of 1
M NH3 with half as much 1 M HCl.
-Mix equal volumes of 1 M NH3 and 1 M NH4 .
a) Phosphoric acid is a triprotic acid (Ka1 = 6.9× 10-3, Ka2 = 6.2× 10-8, and Ka3 = 4.8× 10-13).
To find the pH of a buffer composed of H2PO4-(aq) and HPO42-(aq), which pKa value would
you use in the Henderson-Hasselbalch equation?
pKa1 = 2.16
pKa2 = 7.21
眼睛”主题的中文文章？
pKa3 = 12.32
b)Calculate the pH of a buffer solution obtained by dissolving 24.0 g of KH2PO4(s) and 35.0 g
of Na2HPO4(s) in water and then diluting to 1.00 L. - (answers)a) pka2=7.21
b) 7.35
If a buffer solution is 0.200 M in a weak base (Kb = 4.6 × 10-5) and 0.500 M in its conjugate
acid, what is the pH? - (answers)9.27
You need to prepare 100.0 mL of a pH=4.00 buffer solution using 0.100 M benzoic acid (pKa =
4.20) and 0.240 M sodium benzoate.
If a buffer solution is 0.150 M in a weak acid (Ka = 2.3 × 10-5) and 0.560 M in its conjugate
base, what is the pH? - (answers)5.20
How could you make a buffer? (Select all that apply)
-Partially neutralize a weak acid solution by addition of a strong base.
-Partially neutralize a strong acid solution by addition of a strong base.
-Partially neutralize a strong base solution by addition of a strong acid.
-Partially neutralize a weak base solution by addition of a strong acid.
-Add appropriate quantities of weak acid and its conjugate base to water. - (answers)-Partially
neutralize a weak acid solution by addition of a strong base.
-Partially neutralize a weak base solution by addition of a strong acid.
-Add appropriate quantities of weak acid and its conjugate base to water.
a) Calculate the change in pH眼睛”主题的中文文章？
when 8.00 mL of 0.100 M HCl(aq) is added to 100.0 mL of a
buffer solution that is 0.100 M in NH3(aq) and 0.100 M in NH4Cl(aq). A list of ionization
constants can be found here.
b) Calculate the change in pH when 8.00 mL of 0.100 M NaOH(aq) is added to the original
buffer solution. - (answers)a) -0.07
b) 0.07
Which pair of compounds will form a buffer in aqueous solution?
NaCN and NaOH
NaCN and KCN
HCl and NaCl
HCl and NaOH
, HCN and HCl
HCN and NaCN - (answers)HCN and NaCN
Which of the following are valid ways to make an ammonia/ammonium buffer for use in the
laboratory?
-Mix equal volumes of 1 M NH3 and 1 M NH4 .
-Mix equal volumes of 1 M NH3 and 0.01 M NH4
-Mix equal volumes of 1 M NH3 and 1 M HCl.
-Mix some volume of 1 M NH3 with half as much 1 M HCl. - (answers)-Mix some volume of 1
M NH3 with half as much 1 M HCl.
-Mix equal volumes of 1 M NH3 and 1 M NH4 .
a) Phosphoric acid is a triprotic acid (Ka1 = 6.9× 10-3, Ka2 = 6.2× 10-8, and Ka3 = 4.8× 10-13).
To find the pH of a buffer composed of H2PO4-(aq) and HPO42-(aq), which pKa value would
you use in the Henderson-Hasselbalch equation?
pKa1 = 2.16
pKa2 = 7.21
眼睛”主题的中文文章？
pKa3 = 12.32
b)Calculate the pH of a buffer solution obtained by dissolving 24.0 g of KH2PO4(s) and 35.0 g
of Na2HPO4(s) in water and then diluting to 1.00 L. - (answers)a) pka2=7.21
b) 7.35
If a buffer solution is 0.200 M in a weak base (Kb = 4.6 × 10-5) and 0.500 M in its conjugate
acid, what is the pH? - (answers)9.27
You need to prepare 100.0 mL of a pH=4.00 buffer solution using 0.100 M benzoic acid (pKa =
4.20) and 0.240 M sodium benzoate.
