QUESTIONS

1. From where does the energy come to overcome the attractions between ions when a salt crystal dissolves?

2. What is the distinction between a strong acid and a weak acid? Give an example of each.

3. Are there also both strong and weak bases? If there are, give examples.

4. For an acid that dissociates to release a single proton, what is the general expression for the dissociation constant, K_a?

5. What is the expression for the base-dissociation constant, K_b, for a weak base?

6. It often is convenient to use an acid-dissociation constant, K_a, for a weak base instead of K_b. For NH₃, what is the acid form and what is the expression for K_a? Show that, in general, K_a x K_b = K_w.

7. What is the method of successive approximations, and when can it be used in solving acid-base equilibrium problems?

8. Why does the equilibrium-constant expression for the dissociation of water ordinarily not have an H₂O concentration term in the denominator? What happened to this concentration term? What is this H₂O-dissociation constant commonly called? How does its numerical value depend on temperature, and what value usually is used?

9. How can Le Chatelier's principle and the observed dependence of the ion-product constant upon temperature be used to decide whether the dissociation of water is exothermic or not? Check your prediction against information in Appendix 2.

10. What is the process of counteracting an acid with a base called? What ions are involved in this process, and how do they interact? What is the product?

11. What are the concentrations of H⁺ and OH^- ions in pure water? How do these concentrations change when the solution is made acidic?

12. What is the pH scale, and why is it convenient in expressing hydrogen ion concentration? What is pOH?

13. How are pH and pOH related in aqueous solution? What values, or range of values, do they have in acidic, neutral, and basic solutions?