Download 4 Acid Base Solutions

South Pasadena • AP Chemistry
Name
4 ▪ Acid Base Solutions
Period
4.1
PROBLEMS
–
TYPES OF
ACIDS
Date
AND BASES
1. For each of the following, identify whether they are an acid, base, amphoteric, or neither. Write its conjugate
and dissociation equation.
Type
Compound
−
Conjugate
Dissociation Equation
HBr
(Br− is conjugate of SA)
(a)
Neither
Br
(b)
Base
C2H3O2−
HC2H3O2
HC2H3O2 + H2O  H3O+ + C2H3O2−
(c)
Acid
C5H5NH+
C5H5N
C5H5NH+ + H2O  H3O+ + C5H5N
(d)
Base
C6H5NH2
C6H5NH3+
C6H5NH2 + H2O  C6H5NH3+ + OH−
(e)
Neither
CH3OH
(f)
Base
CN−
HCN
CN− + H2O  HCN + OH−
(g)
Acid
H2CO3
HCO3−
H2CO3 + H2O  H3O+ + HCO3−
(h)
Base
H2NNH2
H2NNH3+
H2NNH2 + H2O  H2NNH3+ + OH−
(i)
Amphiprotic
HCO3−
H2CO3 / CO32−
HCO3− + H2O  H2CO3 + OH−
HCO3− + H2O  CO32− + H3O+
(j)
Acid
HF
F−
HF + H2O  H3O+ + F−
(k)
Acid
HNO3
NO3−
HNO3 → H+ + NO3−
(l)
Acid
HOCl
OCl−
HOCl + H2O  H3O+ + OCl−
(m)
Neither
K+
(n)
Acid
NH4+
NH3
NH4+ + H2O  H3O+ + NH3
(o)
Base
NO2−
HNO2
NO2− + H2O  HNO2 + OH−
(p)
Base
Zn(OH)2
(Alcohols are neither acids nor bases)
(K+ is the cation of a SB)
2. The monohydrogenphosphate ion, HPO42−, is
amphiprotic. Write the chemical equation for the
ion behaving as an acid and as a base. Identify on
the equation the acid, base, conjugate acid, and
conjugate base.
HPO42− + H2O  H3O+ + PO43−
Acid
Base
Conj Acid
Conj Base
Zn(OH)2  Zn2+ + 2 OH−
4. Write the net ionic equations for the acid-base
reactions between:
a. Hydrofluoric acid and sodium hydroxide
HF + OH− → F− + H2O
b. Ammonium chloride and potassium hydroxide
NH4+ + OH− → NH3 + H2O
HPO42− + H2O  H2PO4− + OH−
Base
Acid
Conj Acid
Conj Base
3. Arsenic acid, H3AsO4, is a triprotic acid. Write
the three dissociation equations for this acid.
H3AsO4 + H2O  H3O+ + H2AsO4−
H2AsO4− + H2O  H3O+ + HAsO42−
HAsO42− + H2O  H3O+ + AsO43−
c. Sodium bicarbonate and sulfuric acid
HCO3− + H+ → H2O + CO2
d. Chlorous acid and aqueous ammonia solution
HClO2 + NH3  ClO2− + NH4+
e. Disodium hydrogen phosphate and acetic acid
HPO42− + HC2H3O2  H2PO4− + C2H3O2−
5. Write the balanced molecular equations for the
neutralization reactions to form each salt.
a. Calcium bromate
2 HBrO3 + Ca(OH)2 → Ca(BrO3)2 + 2 H2O
8. Without using a calculator, determine the whole
number pH between which the solution lies.
a. A solution with pOH = 4.2 has a pH between
9.0 and 10.0.
b. Aluminum bisulfate
3 H2SO4 + 2 Al(OH)3 → Al2(SO4)3 + 6 H2O
b. A solution with [H+] = 8.9 × 10−8 M has a pH
between 7.0 and 8.0.
c. Monosodium dihydrogen phosphate
H3PO4 + NaOH → NaH2PO4 + H2O
c. A solution with [OH−] = 4.1 × 10−1 M has a
pH between 13.0 and 14.0.
6. A neutral amino acid is amphoteric. Draw the
structures of its conjugate acid and its conjugate
base.
H
N
H
H
O
C
C
O
H
[H+]
10. Consider the ratio: [OH−] .
R
Conjugate acid:
H
+
N
H
H
H
O
C
C
O
H
R
Conjugate base:
H
N
H
H
O
C
C
O
R
7. Many salts are acidic or basic when dissolved in
water. To determine the acidity of a salt, examine
whether each ion is acidic, basic, or neutral. For
example, NaF is a basic salt because Na+ is neutral
while F− is basic. For each of the following salts,
determine whether its acidic, basic, or neutral in
solution.
a. NH4Cl
Acidic (NH4+)
b. KNO3
Neutral
c. Na2CO3
Base (CO32−)
+
d. C2H5NH3Br
Acid (C2H5NH3 )
e. LiCN
Base (CN−)
f.
Base (C2H3O2−)
CsC2H3O2
g. RbClO4
9. At 0°C, the pH of pure water is 7.47. Find the
value of Kw at this temperature.
[H+] = [OH−] = 10−7.47 = 3.4 × 10−8 M
Kw = [H+][OH−] = (3.4 × 10−8)2 = 1.1 × 10−15
Neutral
a. What is the value of the ratio for:
[H+]
A neutral solution?
=1
[OH−]
[H+]
Acidic solution?
>1
[OH−]
[H+]
Basic solution?
<1
[OH−]
b. Kw of pure water at 40°C is 2.92 × 10−14.
Consider a 0.0010 M solution of HCl. What is
the [OH−] at:
25°C
Kw 1.0 × 10−14
[OH−] = + =
[H ]
0.0010
= 1.0 × 10−11 M
[H+]
1.0 × 10−3
= 1.0 × 108
− =
[OH ] 1.0 × 10−11
40°C
Kw 2.92 × 10−14
[OH−] = + =
[H ]
0.0010
−11
= 2.9 × 10 M
+
[H ]
1.0 × 10−3
=
= 3.4 × 107
[OH−] 2.9 × 10−11
c. Does the solution become more acidic,
become more acidic, or remain unchanged as
[H+]
the temperature increases? Use the [OH−]
ratio to justify your answer.
The solution became less acidic as the
[H+]
temperature increased because the
[OH−]
ratio decreased.