Counterintuitive Examples and Discrepant Events

1. Diluting a weak electrolyte (HC2H3O2) with water increases the electrical conductivity. (See Suggested Laboratory Activity, Strong vs. Weak Acids)

2. Carbon dioxide bubbled through limewater causes a precipitate to form. Continued bubbling causes the precipitate to disappear. (See Underground sculpture, ChemMatters (1984),1(2), pp. 10-11.

3. Some active metals react with either acids or bases to produce hydrogen gas. (For example, aluminum will react with either hydrochloric acid or sodium hydroxide, releasing hydrogen gas. See Suggestions for Other Demonstrations, Making hydrogen gas from an acid and a base.)

4. The same amount of hydrogen gas will be produced when a sample of an active metal is added to equal volumes of concentrated acid solution and dilute acid solution (if the metal is the limiting reactant).

5. Bicarbonate salts can be used to neutralize either an acid or a base. This can be illustrated by the following equations:

Metaphors and Analogies

1. [H⁺] vs. pH: a see-saw relationship (see Pictures in the Mind below); one goes up (increases) while the other goes down (decreases).

2. A proton shifting from an acid to a base can be likened to a baseball being thrown from a pitcher (the acid) to a catcher (the base).

3. Universal indicator color changes follow the colors in the rainbow as the pH moves from 2 to 10. The name ROY G BIV helps keep the colors straight: Red, Orange, Yellow, Green, Blue, Indigo, Violet. A pH of 7 produces a yellow-green hue.

Pictures in the Mind

1. Ionization. Graphical pictorial representation of the behavior of acids of different strengths in aqueous solution.

a) A strong acid is completely dissociated.

b) In a weak acid only a small fraction of molecules is dissociated in solution.

.

.

.

.

.

	TABLE OF CONTENTS	TOPIC OVERVIEW	CONCEPT/SKILLS DEVELOPMENT	LINKS/CONNECTIONS	EXTENSIONS