South Pasadena AP Chemistry
18
1.
Name _______________________________
Period ___ Date ___/___/___
Acid-Base Reactions
¯10
HCN is a weak acid (Ka = 6.2 x 10 ). NH3
is a weak base (Kb = 1.8 x 10¯5). A 1.0 M
solution of NH4CN would be
a) strongly acidic
c) neutral
b) weakly acidic
d) weakly basic
2. If you mix equal molar quantities of NH3
(Kb = 1.8 x 10 5) and HF (Ka = 7.2 x 10 4),
the resulting solution will be
a) acidic because Ka of NH4+ > Kb for F
b) acidic because Ka of NH4+ > Ka for HF
c) basic because Kb of NH4+ > Kb for F
d) basic because Ka of NH4+ > Kb for F
e) neutral
3.
4.
How many moles of HCOONa must be
added to 1.0 L of 0.10 M HCOOH to
prepare a buffer solution with a pH of 3.4?
(HCOOH Ka = 2 x 10¯4)
a) 0.01
c) 0.1
b) 0.05
d) 0.2
The acid-base indicator methyl red has a Ka
of 1 x 10¯4. Its acidic form is red while its
alkaline form is yellow. If methyl red is
added to a colorless solution with a pH = 7,
the color will be
a) pink
c) orange
b) red
d) yellow
5. Which would make the best aqueous buffer
solution?
a) 0.30 M NH3 / 0.30 M NH4Cl
b) 0.010 M NH3 / 0.30 M NH4Cl
c) 0.10 M NH3 / 0.20 M HCl
d) 0.30 M KOH / 0.30 M HCl
P R A C T I C E T E S T
6. If you mix equal molar quantities of the
following substances, how many will
produce an acidic solution?
Set 1: NaOH + HCl
Set 2: NaOH + HNO3
Set 3: NH3 + HCl
Set 4: NaOH + HC2H3O2
a) four
d) one
b) three
e) zero (none)
c) two
7. A 25.0 mL sample of a 0.20 M solution of a
weak monoprotic acid is titrated with a 0.10
M KOH solution. What volume of base is
needed to reach the equivalence point?
a) 20.0 mL
c) 35.0 mL
b) 25.0 mL
d) 50.0 mL
8. We add 200. mL of 0.10 M KOH to 50.0 mL
of 0.40 M HF. What is the pH of the
resulting solution? Kb for F = 1.4 x 10 11
a) 5.97
d) 8.37
b) 6.32
e) 9.32
c) 8.02
9. What are the products of the following acidbase reaction?
NaOH(aq) + HF(aq)
a) NaF(aq) and H2O(l)
b) NaH(aq) and HOF(aq)
c) H2O only.
d) H2O(l), F2(aq), and Na(s)
e) NaF(aq) and OH (aq)
10. The titration curve below represents the
titration of a weak acid with a strong base.
Use the sample data below to answer the
next 4 questions.
PART I STANDARDIZATION OF THE
BASE with Solid Acid
Trial #1
What is the Ka of the weak acid?
a) 1.6 x 10-4
c) 1.0 x 10-7
b) 2.0 x 10-6
d) 1.0 x 10-9
11. The salt produced by the reaction of an equal
number of moles of KOH and HNO3 will
react with water to give a solution which is
a) acidic.
d) non-ionic.
b) basic.
e) impossible to
c) neutral.
determine.
12. If you mix 100. mL of 0.11 M HCl with 50.0
mL of 0.22 M NH3, what is the pH of the
resulting solution?
The Ka of NH4+ = 5.6 x 10 10
a) 4.63
d) 8.37
b) 5.19
e) 9.37
c) 6.02
Acid
Base
(NaOH)
Final
Value
Initial
Value
Mass or
Volume
Used
2.56
grams
3.28
grams
?
22.50
mL
0.00 mL
Trial #2
Acid
Base
(NaOH)
Final
Value
Initial
Value
Mass or
Volume
Used
1.85
grams
2.56
grams
?
RATIO:
vol base /
mass acid
?
RATIO:
vol base /
mass acid
45.50 mL
22.50 mL
?
13. What is the percentage difference between
the two calculated ratios for trials 1 and 2?
a) 0.45 %
c) 2.4 %
b) 1.2 %
d) 3.5 %
14. Based on the answer to question #21, should
this student run a third trial for Part I?
a) Yes
b) No
c) More information is needed
15. If the solid acid used above was potassium
hydrogen tartrate (KHC4H4O6 M.W. =
188.15), how many moles of OH in trial #1
were needed to completely neutralize the
acid?
a) 0.0174 moles
b) 0.00766 moles
c) 0.00377 moles
d) 0.00383 moles
16. Based on the data from trial #2, what is
the calculated concentration of the NaOH?
a) 0.16 M
c) 0.19 M
b) 0.18 M
d) 0.20 M
**************************
17. A 10.0 mL sample of 0.15 M HCl is titrated
with an NaOH solution. When a 10.0 mL
sample of 0.15 M HF (Ka = 7.2 x 10 4) is
used, the volume of base needed is
a) the same
d) slightly more
b) much more
e) slightly less
c) much less
18. A buffer solution is prepared with a pH of
5.50. The solution is diluted by adding an
equal volume of distilled H2O. The pH of
the solution will
a) increase slightly
b) decrease slightly
c) increase greatly
d) decrease greatly
e) remain the same
19. Which graph shows a strong base being
titrated with a strong acid?
20. If you titrate HC2H3O2 with NaOH, what
species are present at the endpoint?
a) Na+, C2H3O2 , OH , and H2O
b) Na+, C2H3O2 , HC2H3O2, OH , and H2O
c) Na+, HC2H3O2, OH , and H2O
d) Na+, C2H3O2 , H3O+, and H2O
e) Na+, HC2H3O2, H3O+, and H2O
21. In the titration lab, the student is supposed to
dissolve the solid acid in 50.0 mL of water.
How would the amount of base needed
change if 100. mL of water was used instead?
a) increase greatly
d) decrease slightly
b) increase slightly
e) decrease greatly
c) not change
Answers to Practice Test:
1.
11.
2.
12.
3.
13.
4.
14.
5.
15.
6.
16.
7.
17.
8.
18.
9.
19.
10.
20.
21.
a) Graph (A)
b) Graph (B)
c) Graph (C)
d) Graph (D)
e) none of these
Answers to Practice Test:
1.
D
11.
C
2.
A
12.
B
3.
B
13.
D
4.
D
14.
A
5.
A
15.
D
6.
D
16.
A
7.
D
17.
A
8.
C
18.
E
9.
A
19.
C
10.
A
20.
B
21.
C
Formulas from the AP Exam: