Chapter 14 · Acids and Bases
14.7Strong and Weak Acids and Bases
11 min · two checks
Predict
Does a 1 M weak acid contain about 1 M H₃O⁺?
The idea
- Separate strong from weak, and concentrated from dilute.
- Recognize the common strong acids and bases.
A strong acid ionizes completely: HCl → H⁺ + Cl⁻ goes to completion, so 0.10 M HCl is 0.10 M in H₃O⁺. The strong acids to memorize: HCl, HBr, HI, HNO₃, HClO₄, H₂SO₄ (first proton). A weak acid sets up an equilibrium and remains mostly molecules. Vinegar is concentrated enough to taste and still weak. “Strong” never meant “dangerous concentration.” A dilute strong acid can be milder than a concentrated weak acid, and the words answer different questions.
Strong bases ionize completely and are the soluble hydroxides: NaOH, KOH, and the other Group 1 hydroxides, plus Ca(OH)₂, Sr(OH)₂, and Ba(OH)₂ for many problems. Ammonia and most amines are weak bases. In a net ionic equation, split strong acids and strong hydroxide bases. Leave weak acids, weak bases, and water written as molecules.
Keep these
- Strong: complete ionization. Weak: partial, an equilibrium.
- Concentration is separate from strength.
- Memorize the six strong acids and the soluble strong hydroxides.