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Chemistry Chapter 19.3. Strengths of Acids and Bases. Strong and Weak Acids and Bases. Acids and bases are classified as strong or weak according to the degree to which they ionize in water. Strong acids are completely ionized in aqueous solution.
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Chemistry Chapter 19.3 Strengths of Acids and Bases
Strong and Weak Acids and Bases • Acids and bases are classified as strong or weak according to the degree to which they ionize in water. • Strong acids are completely ionized in aqueous solution. • Examples: Hydrochloric acid and sulfuric acid. • HCl(g) + H2O(l) → H3O+(aq)+ Cl- (aq) • HCl dissociates completely (100%) into ions when dissolved in water.
Weak acids ionize only slightly in aqueous solution. • Example: Acetic (ethanoic) acid • CH3COOH(aq) + H2O(l) ⇄ H30+(aq) + CH3COO-(aq) • The ionization is not complete. • The same principle is true for strong bases and weak bases.
Concentration and Strength • The strength or weakness of an acid or base ( the degree of ionization that occurs) is independent of its concentration. • The words concentrated and dilute refer to how much of an acid or base is dissolved in solution. • When you have a dilute solution of hydrochloric acid, it is still a strong acid (gastric juice). • Vinegar (acetic acid) is a dilute solution of a weak acid…a sample of pure acetic acid would still be a weak acid.
Salts in Solution (19.5) • Salts consist of an anion from an acid and a cation from a base. • Some salt solutions may be acidic or basic, but many are neutral (NaCl). • In general, salts that produce acidic solutions contain positive ions that release protons to water. Salts that produce basic solutions contain negative ions that attract protons from water.