Chapter 21 Neutralization Neutralization Reactions Salts in Solution

Common Indicators IndicatorColor ChangepH Range Methyl RedRed - Yellow4.3 – 6.2 Phenol RedYellow - Red6.9 – 8.2 Alizarin YellowYellow - Pink10.0 – 12.0 PhenolpthaleinClear - Pink Congo RedBlue - Red3.0 – 5.2 Bromothymol BlueYellow - Blue6.0 – 7.5

Acid-Base Reactions Acid + Base  Salt + Water Salt – Compounds made up of anions from an acid and cations from a base

Neutralization Reaction Strong Acid + Strong Base  Salt and Water The number of hydronium ions must equal the number of hydroxide ions A reaction of a weak acid and weak base do not usually produce neutral solutions

Salts Ammonium Sulfate – Fertilizer Calcium Chloride – Road Salt Potassium Chloride – Sodium Free Salt Substitute Silver Nitrate - Cauterizing Agent Sodium Hydrogen Carbonate - Antacid

Titration Process of adding a known amount of a solution of known concentration to determine the concentration of another solution End Point – the point where the indicator changes color

Ch 21.2 Salts in Solution Salt Hydrolysis Buffers Common Ion Effect

Salt Hydrolysis Reaction of a strong acid and a weak base or a strong base and a weak acid The salt may be acidic or basic, not neutral (strong acid – strong base reaction) CH 3 COO - (aq) + H 2 O (l)  CH 3 COOH (aq) + OH - (aq) Hydrolysis – splits a hydrogen off a water molecule

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

Buffer The pH remains relatively constant with the addition of small amounts of acid or base Made up of a solution of a weak acid and its salt or a weak base and its salt

Human Blood Two main buffers to keep pH – Carbonic acid-hydrogen carbonate buffer system – Dihydrogen phosphate – monohydrogen phosphate buffer system

Common Ion Effect The lowering of solubility of a substance by the addition of a common ion