AP Chemistry – Chapter 14 Review Packet
Name______________________________
1.
For the stepwise dissociation of aqueous H3PO4, which of the following is NOT a
conjugate acid-base pair?
H3PO4 + H2O ↔ H3O+1 + H2PO41
2
3
a. HPO4 and PO4
acid
base
c.a.
c.b.
b. H3PO4 and H2PO41
c. H2PO41 and HPO42
H2PO41 + H2O ↔ H3O+1 + HPO42
1
3
d. H2PO4 and PO4
acid
base
c.a.
c.b.
e. H3O+1 and H2O
HPO42 + H2O ↔ H3O+1 + PO43
acid
base
c.a.
c.b.
2.
What is the equilibrium constant for the following reaction?
N31 + H3O+1 ↔ HN3 + H2O
The Ka value for HN3 = 1.9 x 105
a. 5.3 x 1010
b. 1.9 x 109
c. 1.9 x 105
d. 5.3 x 104
e. 1.9 x 109
3.
K = 1/Ka = 1/(1.9 x 105) = 5.3 x 104
The hydrogen sulfate (or bisulfate) ion HSO41 can act as either an acid or a base in water
solution. In which of the following equations does HSO41 act as an acid?
a.
b.
c.
d.
e.
HSO41 + H2O → H2SO4 + OH1
HSO41 + H3O+1 → SO3 + 2 H2O
HSO41 + OH1 → H2SO4 + O2
HSO41 + H2O → SO42 + H3O+1
none of these
HSO41 + OH1 → H2SO4 + O2
base
acid
c.a.
c.b.
4.
HN3 + H2O ↔ H3O+1 + N31
Ka = 1.9 x 105
So K for the given rxn is 1/Ka or
HSO41 + H2O → H2SO4 + OH1
base
acid
c.a.
c.b.
HSO41 + H3O+1 → SO3 + 2 H2O
base
acid
c.a.
c.b.
HSO41 + H2O → SO42 + H3O+1
acid
base
c.b.
c.a.
Using the following Ka values, indicate the correct order of base strength.
HNO2
Ka = 4.0 x 104
HCl > HF > HNO2 > H2O > HCN
HF
Ka = 7.2 x 104
Because
HCN
Ka = 6.2 x 1010
KaHCl > KaHF > KaHNO2 > KaH2O > KaHCN
Therefore
a. CN1 > NO21 > F1 > H2O > Cl1
Cl1 < F1 < NO21 < H2O <CN1
b. Cl1 > H2O > F1 > NO21 > CN1
c. CN1 > F1 > NO21 > Cl1 > H2O
d. H2O > CN1 > NO21 > F1 > Cl1
e. none of these
5.
Which of the following is the equilibrium constant expression for the dissociation of the
weak acid HOCl?
a. K = [H+1] [OCl1]
HOCl + H2O ↔ H3O+1 + OCl1
[HOCl]
+1
1
b. K = [H ] [OCl ]
c. K =
Ka = [H3O+1] [OCl1]
[HOCl]
[HOCl]____
[H+1] [OCl1]
d. K = [H+1] [O2] Cl1]
[HOCl]
e. none of these
Use the following equations for questions 6 and 7. The following three equations represent
equilibria that lie far to the right.
HNO3 (aq) + CN−1 (aq) ↔ HCN (aq) + NO3−1 (aq)
acid
base
c.a.
c.b.
HCN (aq) + OH−1 (aq) ↔ H2O (ℓ) + CN−1 (aq)
acid
base
c.a.
c.b.
H2O (ℓ) + CH3O−1 (aq) ↔ CH3OH (aq) + OH−1 (aq)
acid
base
c.a.
c.b.
6.
Identify the strongest acid.
a. HCN – weak acid
b. HNO3 – strong acid
c. H2O - neutral
d. OH−1 – strong base
e. CH3OH – weak acid
Acid Strength:
HNO3 > HCN or CH3OH > H2O > OH1
Therefore, Base Strength:
NO31 < CN1 or CH3O1 < OH1 < O2
Because the equilibriums lie far to the right:
CN−1 is a stronger base then NO3−1
OH−1 is a stronger base then CN−1
CH3O−1 is a stronger base then OH−1
therefore, the strongest base is CH3O−1
7.
Identify the strongest base.
a. CH3O−1
b. CH3OH
c. CN−1
d. H2O
e. NO3−1
8.
In which of the following reactions does the H2PO41 ion act as an acid?
a. H3PO4 + H2O ↔ H3O+1 + H2PO41
See work on question #1
b. H2PO41 + H2O ↔ H3O+1 + HPO42
1
1
2
c. H2PO4 + OH ↔ H3PO4 + O
d. The ion cannot act as an acid.
e. Two of these
9.
Which of the following is true for the dissociation of a weak acid?
a. Ka is large.
HA ↔ H+1 + A−1
b. The equilibrium lies far to the right. Ka = [H+1] [A−1]
c. The equilibrium lies far to the left.
[HA]
d. [H+1] >>[HA]
A weak acid’s equilibrium will lie to the left.
e. The conjugate base will be weak.
(For the equilibrium to lie to the right, it has to be
a strong acid. For a strong acid, [H+1] >>[HA].)
10.
Which of the following reactions is associated with the definition of Kb?
a. Zn(OH)6+2 ↔ [Zn(OH)5(OH)]+1 + H+1
b. CN1 + H+1 ↔ HCN
Kb always refers to the reaction of a base with
c. F1 + H2O ↔ HF + OH1
+3
+3
water
to form the conjugate acid and the
d. Cr + 6 H2O ↔ Cr(OH2)6
hydroxide ion (conjugate base.)
e. none of these
11.
Use the following Ka’s to answer the question.
HAc
Ka = 1.8 x 105
H2CO3
Ka1 = 4.3 x 107
Ka2 = 5.6 x 1011
a.
b.
c.
d.
e.
HAc
NaAc
Na2CO3
H2CO3
NaHCO3
OMIT
H2CO3 + H2O ↔ H3O+1 + HCO31
acid
base
c.a.
c.b.
HCO31 + H2O ↔ H3O+1 + CO32
acid
base
c.a.
c.b.
12.
The conjugate acid and conjugate base of the bicarbonate ion, HCO31, are, respectively:
a. H3O+1 and OH1
b. H3O+1 and CO32
See work on question #11
c. H2CO3 and OH1
2
d. H2CO3 and CO3
e. CO32 and OH1
13.
Which of the following species is present in the greatest concentration in a 0.100 M
H2SO4 solution in H2O?
a. H3O+1
H2SO4 + H2O → H3O+1 + HSO41
dissociates
1
b. HSO4
acid
base
c.a.
c.b.
completely
c. H2SO4
d. All species are in
HSO41 + H2O ↔ H3O+1 + SO42
equilibrium and
acid
base
c.a.
c.b.
therefore have the
same concentration.
e. SO42
14.
The sodium salt, NaA, of a weak acid is dissolved in water; no other substance is added.
Which of these statements (to a close approximation) is true?
a. [H+1] = [A1]
NaA → Na+1 + A1
dissociates completely
b. [H+1] = [OH1]
1
+1
So [A ] is large. [H ] is not in either reaction.
c. [A1] = [OH1]
A1 + H2O ↔ HA + OH1
d. [HA] = [OH1]
[HA] = [OH1], 1:1 ratio; The exact concentration
e. none of these
depends on the percent dissociation.
15.
The hydrogen halides (HF, HCl, HBr, and HI) are all polar molecules. The strength of
the acid each forms in water is based on which of the following?
a. the polarity of the moelcule As electronegativity increases, acid strength increases.
b. the size of the molecule
As the strength of the H-X bond increases, acid
c. the strength of the bond
strength increases.
d. two of these
(Answers “a” and “c” are correct.
e. none of these
16.
Which factor listed below is most important in determining the strength of an oxyacid?
a. the size of the molecule
b. the ability of the molecule to change atomic orientation Acid strength increases
with an increase in the
c. the identity of the central atom in the molecule
number of oxygen
d. the number of oxygen atoms present in the molecule
atoms attached to the
e. none of these
central atom.
For questions 17-19, use the following information.
If the following substance is dissolved in pure water, will the solution be acidic, neutral,
or basic?
This is a tug-of-war. Strong-strong is a tie (neutral).
a. Acidic
In a weak-strong situation, the strong one always wins.
b. Neutral
c. Basic
17.
solid sodium nitrate b. Neutral
NaNO3 Na comes from NaOH, a strong base and NO3 comes from HNO3, a strong acid.
18.
solid silver chloride a. Acidic
AgCl Ag comes from AgOH, a weak base and Cl comes from HCl, a strong acid.
19.
solid sodium carbonate c. Basic
Na2CO3 Na comes from NaOH, a strong base; CO3 comes from H2CO3, a strong acid.
20.
As water is heated, its pH decreases. This means that
a. the water is no longer neutral.
b. the Kw value is decreasing.
c. the water has a lower [OH−1] than cooler water.
d. the dissociation of water is an endothermic process.
e. none of these