Chemistry (Chang), 9th EditionChapter 15:
Acids and BasesChapter Summary1. Brönsted acids donate protons, and Brønsted bases accept protons. These are the
definitions that normally underlie the use of the terms “acid” and “base.”
2. The acidity of an aqueous solution is expressed as its pH, which is defined as the
negative logarithm of the hydrogen ion concentration (in mol/L).
3. At 25°C, an acidic solution has pH < 7, a basic solution has pH > 7, and a neutral solution has pH = 7.
4. In aqueous solution, the following are classified as strong acids: HClO4, HI, HBr, HCl, H2SO4 (first stage of ionization), and HNO3. Strong bases in aqueous solution include hydroxides of alkali metals and of alkaline earth metals (except beryllium).
5. The acid ionization constant Ka increases with acid strength. Kb similarly expresses the strengths of bases.
6. Percent ionization is another measure of the strength of acids. The more dilute a
solution of a weak acid, the greater the percent ionization of the acid.
7. The product of the ionization constant of an acid and the ionization constant of its
conjugate base is equal to the ion-product constant of water.
8. The relative strengths of acids can be explained qualitatively in terms of their
molecular structures.
9. Most salts are strong electrolytes that dissociate completely into ions in solution.
The reaction of these ions with water, called salt hydrolysis, can produce acidic or
basic solutions. In salt hydrolysis, the conjugate bases of weak acids yield basic
solutions, and the conjugate acids of weak bases yield acidic solutions.
10. Small, highly charged metal ions, such as Al3+ and Fe3+, hydrolyze to yield acidic
solutions.
11. Most oxides can be classified as acidic, basic, or amphoteric. Metal hydroxides are
either basic or amphoteric.
12. Lewis acids accept pairs of electrons and Lewis bases donate pairs of electrons.
The term “Lewis acid” is generally reserved for substances that can accept electron
pairs but do not contain ionizable hydrogen atoms.
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