__‘_91 EXAM 3 Spring 2026
_AME; E-mail: EXAM GRADE:
Question 1 (5 points
Which of the following statements is NOT true for a buffer solution?
A. Buffer is a mixture of a weak acid and its conjugate base.
B. Buffer is a mixture of a weak base and its conjugate acid.
@ Buffer solution resists pH changes at all times.
D. Buffer capacity is the greatest when pH is equal to pKa.
E. Buffer reacts with the acid and base added.
Question 2 {5 points)
Which weak acid would be best to use when preparing a buffer solution with a pH of 4.8?
@An acid with K,=2.5x10"5
B. An acid with K,=2.5x1078
C. An acid with K3=3.2x1077
D. An acid with K;=1.7x107%0
E. An acid with K;=1.0x10™1
Question 3 (5 points)
At which point of a titration pH is equal to pKa?
(V is for volume of titrant added, Ve is for equivalence point volume)
A. atV=0mL
B. atV=Ve
C.\atV=1/2 Ve
D. atV=2Ve
E. atV=1/5Ve
, CHEM 2001 EXAM 3 Spring 2026
Question 4 (6 points)
Fill in the blanks below.
et S EQUiVPEP(E is the point when the quantity of titrant added is the exact amount necessary
for stoichiometric reaction with analyte.
3pt) £ pereT isthe point that is marked by a sudden change in the physical property of the
solution when a titrant is added to the analyte during a titration.
Question 5 (5 points)
The dissociation of lactic acid to lactate is shown in the reaction. Lactic acid has a pKa of 7.18.
0 0
OH 0
S
Lactic acid
on Lactate A
A solution containing a mixture of lactic acid and lactate was found to have a pH of 7.55. Calculate the
ratio of the lactate concentration to the lactic acid concentration in this solution. Show your work for
partial or full credit.
= o Pka +é Wl
o] o7 tss-tag e/?UMI
K] e
o
031
= ZEoe} 2e¢s
(kA
~ [A‘l ¢
¢
2.39°¢ mfi lv
Question 6 (22 points)
A 40 mL of 0.3 M monoprotic base is titrated with a 0.4 M strong acid. Weak base has Ky value of 2.4 x
103, Show your work for partial or full credit.
A. What is the volume required to reach the equivalence point in mL?
0.4M
_AME; E-mail: EXAM GRADE:
Question 1 (5 points
Which of the following statements is NOT true for a buffer solution?
A. Buffer is a mixture of a weak acid and its conjugate base.
B. Buffer is a mixture of a weak base and its conjugate acid.
@ Buffer solution resists pH changes at all times.
D. Buffer capacity is the greatest when pH is equal to pKa.
E. Buffer reacts with the acid and base added.
Question 2 {5 points)
Which weak acid would be best to use when preparing a buffer solution with a pH of 4.8?
@An acid with K,=2.5x10"5
B. An acid with K,=2.5x1078
C. An acid with K3=3.2x1077
D. An acid with K;=1.7x107%0
E. An acid with K;=1.0x10™1
Question 3 (5 points)
At which point of a titration pH is equal to pKa?
(V is for volume of titrant added, Ve is for equivalence point volume)
A. atV=0mL
B. atV=Ve
C.\atV=1/2 Ve
D. atV=2Ve
E. atV=1/5Ve
, CHEM 2001 EXAM 3 Spring 2026
Question 4 (6 points)
Fill in the blanks below.
et S EQUiVPEP(E is the point when the quantity of titrant added is the exact amount necessary
for stoichiometric reaction with analyte.
3pt) £ pereT isthe point that is marked by a sudden change in the physical property of the
solution when a titrant is added to the analyte during a titration.
Question 5 (5 points)
The dissociation of lactic acid to lactate is shown in the reaction. Lactic acid has a pKa of 7.18.
0 0
OH 0
S
Lactic acid
on Lactate A
A solution containing a mixture of lactic acid and lactate was found to have a pH of 7.55. Calculate the
ratio of the lactate concentration to the lactic acid concentration in this solution. Show your work for
partial or full credit.
= o Pka +é Wl
o] o7 tss-tag e/?UMI
K] e
o
031
= ZEoe} 2e¢s
(kA
~ [A‘l ¢
¢
2.39°¢ mfi lv
Question 6 (22 points)
A 40 mL of 0.3 M monoprotic base is titrated with a 0.4 M strong acid. Weak base has Ky value of 2.4 x
103, Show your work for partial or full credit.
A. What is the volume required to reach the equivalence point in mL?
0.4M
