Chem 1405 Homework chap9
1. Which of the following substances would be classified as an acid? (Section 9.2)
a. LiOH
b. HI
c. NaCl
2. The pH of wine is approximately 3.5. Calculate the hydrogen ion concentration in
wine. (Section 9.3)
a. 3.2 × 10-4 M
b. 3.2 × 103 M
c. 3.5 M
Hint: [H+] = 10-pH
3. Calculate the pH of a 0.045 M solution of HBr, strong acid. (Section 9.3)
a. -1.3
b. 1.3
c. 1.1
Hint: HBr is a strong acid, which will completely dissociate in to ions pH=-log0.045=1.3
4. The pH of household ammonia is approximately 12. Calculate the concentration of
hydroxide ion in ammonia. (Section 9.3)
a. 0.010 M
b. 1.1 M
c. 1 × 10-12 M
Hint:pOH=14-pH=2, [OH-] = 10-pOH=10-2
5. The pH of tomato juice is 3.8. What is the pOH of tomato juice? (Section 9.3)
a. 3.8
b. 10.8
c. 10.2
Hint: pOH=14-pH
6.
a.
b.
c.
Which of the following statements about a weak acid is NOT true? (Section 9.4)
Weak acids do not contain a dissociable hydrogen.
Weak acids react only partly with water.
Weak acids dissociate only partially.
7. Which of the following acids would be the weakest: nitrous acid (pKa = 3.35); formic
acid (pKa = 3.75); carbonic acid (pKa = 6.35)? (Section 9.4)
a. Nitrous acid
b. Formic acid
c. Carbonic acid
8. Identify the conjugate base of the amino acid glycine (NC2H5O2H) in the reaction
NC2H5O2H(aq) + H2O(l)  NC2H5O2-(aq) + H3O+(aq). (Section 9.5)
a. NC2H5O2H
b. NC2H5O2c. H3O+
9. Given that the pKa for ammonium is 9.24, calculate the pKb of ammonia. (Section
9.5)
a. -9.24
b. 23.2
c. 4.76
Hint:pKa +pKb=14
10. Which of the following acids would be classified as polyprotic? (Section 9.6)
a. HCl
b. CH3COOH
c. H3PO4
11. Predict whether the salt sodium acetate, NaCH3COO, will produce a neutral, acidic,
or basic solution when dissolved in water. (Section 9.7)
a. Neutral
b. Acidic
c. Basic
Hint: NaCH3COO dissociate in water into Na+ + CH3COO-. Only CH3COO- will
hydrolyze. CH3COO- + H2O  CH3COOH +OH-
12. Calculate the pH of a solution containing 0.1 M formic acid (HCOOH) and 0.15 M
calcium formate (Ca(HCOO)2). The pKa of formic acid is 3.75. (Section 9.8)
a. 4.2
b. 3.9
c. 5.9
Hint:pH= pKa+log(concentration of conjugate base/concentration of acid)=
3.75+log(0.15/0.1)=3.9
13. A water pool in an abandoned mine has been shown to be contaminated with sulfuric
acid, H2SO4. A 20.0-mL sample of water requires 19.74 mL of 0.45-M NaOH to reach
the stoichiometric point. Calculate the concentration of H2SO4 in the mine water.
(Section 9.10)
a. 222 M
b. 0.44 M
c. 0.22 M
Hint: H2SO4 + 2NaOH  Na2SO4 + 2H2O
nNaOH= MV= 0.0194Lx0.45M= 0.00873mol
n H2SO4 = nNaOH x ( 1mol H2SO4 /2 mol NaOH)= 0.00873/2= 0.00437mol = MxV
M= 0.00437mol/0.02L=0.22M
14. 11. Predict whether the salt sodium acetate, AlCl3, will produce a neutral, acidic, or
basic solution when dissolved in water. (Section 9.7)
a. Neutral
b. Acidic
c. Basic
Hint: AlCl3dissociate in water into Al3+ and Cl- Only Al3+ will hydrolyze. Al3+ + 3H2O
 Al(OH)3+3H+