pH Scale Strengths of Acids and Bases Chapter 23.2 pH Scale Strengths of Acids and Bases

Strong and Weak Acids Strong acid: nearly all the acid molecules dissociate into ions Example: HCl, Sulfuric Acid Weak acid: only a small fraction of molecules dissolve in water Example: vinegar

Strong and Weak Bases Strong base: Dissociates completely in a solution. Example: Sodium hydroxide Weak base: does not dissociate completely in a solution Example: ammonia

Indicators Indicator: Organic substance that changes color in an acid or base Examples: litmus - red/blue phenolphthalein - colorless/pink red cabbage juice - pink/green

pH of a Solution The pH of a solution is a measure of the concentration of H+ ions in it. The pH measures how acidic or basic a solution is. The greater the H+ concentration is, the lower the pH is and the more acidic the solution is.

pH Scale pH Scale ranges from 0 to 14 Less than 7 = Acid Equal to 7 = neutral Greater than 7 = Base 7 INCREASING ACIDITY NEUTRAL BASICITY 14

How to remember what’s what Acid comes before Base in the alphabet Low numbers come before high numbers Acids = low numbers Bases = high numbers

pH of Common Substances pH Scale pH of Common Substances