This lesson begins with the definition of a Bronsted acid-base reaction: a proton transfer. Such a transfer is animated. The student is presented with reactions, and is asked to point to the proton donor, the proton acceptor, the acid, or the base. It is noted that some substances, notably water, may be acids or bases depending on what they react with.
Next, conjugate acids and bases are introduced, and the student is requested to find conjugate pairs in various reactions.
The student discovers that when something reacts with water as an acid, H3O+ is produced, and when something reacts as a base with water, OH- is produced. The dissociation constant, Ka, is introduced as a measure of strength.
These reactions are all graphically illustrated in a full-screen model of water structure, in which H3O+ appears as a proton-rich cluster, and OH- as a proton-deficient one.
Acids are qualitatively classified as strong (compete reaction), weak (partial reaction) and very weak (no reaction). Bases are correspondingly classified. One finds that it is easy to determine all of the approximate ionic concentrations in a solution of a strong acid or base. There is practice in recognising what ionic concentrations are appropriate to solutions of all six types (strong, weak, very weak acid or base) in water.
The final review quiz tests all of the concepts, and includes a challenging question in which solutions are modeled graphically, and the student must identify one in terms of the six types defined in the lesson.
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Updated July 18, 2000