Salts in Solution Mrs. Coyle

Solutions of Salts -Strong Acids and Strong Bases Produce a neutral solution (pH=7) Example: HCl + NaOH  NaCl + H 2 O Strong Acid Strong Base Neutral Solution

Solutions of Salts -Strong Acids and Weak Bases Produce an acidic solution (pH<7) Example: HCl + NH 3  NH 4 Cl + H 2 O Strong Acid Weak Base Acidic Solution

Solutions of Salts -Weak Acids and Strong Bases Produce a basic solution (pH>7) Example: H 2 C O 3 + KOH  K 2 C O 3 + H 2 O Weak Acid Strong Base Basic Solution

Solutions of Salts -Weak Acids and Weak Bases The pH of their salt’s solution depends on their relative strength.

Summary Strong Acid + Strong Base  Neutral Solution Strong Acid + Weak Base  Acidic Solution Weak Acid + Strong Base  Basic Solution

Why does this happen? Salt Hydrolysis Ions of the dissociated salt, remove or donate H +, to the solution.

Example NH 4 Cl (aq)  NH 4 + (aq) + Cl - (aq) NH 4 + (aq) + H 2 O (l)  NH 3 (aq) + H 3 O + (aq) The H 3 O + concentration is greater than that of OH -, so the solution is acidic.

Titration of Weak Acid with Strong Base Equivalence Point is pH=8.7 Note: Equivalence point of pH=7 for HCl(strong) and NaOH(strong)

Buffers Solution in which the pH remains relatively constant when a small amount of acid or base is added to the solution. They are generally a weak acid and its salt or a weak base and its salt.

Examples of Buffers H 2 CO 3 and the salt of HCO 3 - (in human blood) NH 3 and the salt of NH 4 +

Indicators