5.112 Problem Set on Acids and Bases
Instructions: show all your work.
1. What is the % deprotonation of chlorous acid if the pH (aqueous solution) is 3.37? Hint:
Table 10.1 in your text will be helpful.
2. Draw a Lewis structure for chlorous acid. For each atom in the chlorous acid molecule
indicate (using δ+ or δ−) the expected partial charge.
3. What property of a solvent medium favors ionization of a Brønsted acid?
4. Draw Lewis dot structures for chlorous acid and hypochlorous acid, identify which is the
stronger acid and explain why.
5. Calculate the % deprotonation and pH of a 0.10 M aqueous solution of benzoic acid.
6. Draw the chemical structures of benzoic acid and trichloroacetic acid. Compare them in terms
of acidity and discuss their pKa values with reference to molecular structure.
7. The pKa of benzoic acid is lower than that of acetic acid. Which is the stronger acid?
8. Calculate the % deprotonation and pH of a 0.00015 M aqueous solution of hydrochloric acid.
9. A 0.35 M solution of a weak acid has a pH of 4.50. What is the value of Ka for the weak acid?
10. Calculate the % deprotonation and pH of a 0.00015 M aqueous solution of hypoiodous acid.
11. All three chloride ions per Al center become ionized when AlCl3 is dissolved in H2O and the
resulting solution has an acidic pH. What is going on?
12. Give an example of an amphoteric oxide, and explain what differentiates an amphoteric oxide
from an acidic or a basic oxide.
13. Draw the pink form of the indicator molecule phenolphthalein and discuss the structural
changes that accompany the colorless to pink indicator change.
14. Give a derivation of the Henderson-Hasselbalch equation and explain for what purpose it is
useful.
15. Answer the following questions from chapter 11 of your textbook: 11.2, 11.6, 11.12, 11.32.
16. Analyze Figure 11.14 in your text, page 426, with explanation of the significance of points
marked A-D.
Problems below this line are “extra problems” designed to help you prepare for the exam. They
will not be graded.
1. Explain the connection between hydrogen bonding and the rapid rate at which protons are
transported through water.
2. What is the pH of a 0.01 M aqueous solution of NaCl?
3. What is autoprotolysis and why must it be taken into account when calculating the pH of
dilute acid solutions?
4. Answer problems 11.22 and 11.38 from your textbook.
5. Explain the basis for the assumptions used in deriving the Henderson-Hasselbalch equation.
6. Why do you not need to know the pKa for HCl in order to calculate the pH of 0.10 M HCl?
7. If the conjugate base of an acid is a very weak base, then what can you say about the acid?
8. Within the donor/acceptor context, why is it correct to say that electrons are the currency of
chemistry?