Chapter 8

Acids, Bases, and pH

The pH scale

• pH scale is labeled 0-14

• 7 = neutral

• 0-7 = acids, 7-14 = bases

• “weak”, closer to 7

• “strong”, closer to 0 or 14

Acids (0-7)

• A compound that produces hydronium (H30+) ions when dissolved in H20

• Example: HCl + H20 H30+ + Cl-

• Sour taste, react with metals, produce color changes in indicators

• Examples: fruit, shampoo, vinegar

Bases (7-14)

• A compound that produces hydroxide ions (OH-) when dissolved in H20

• Example: NaOH + H2O Na+ + OH-

• Bitter taste, slippery feel, produces color changes in indicators.

• Example: deodorant, Tums (antacid), soap

Neutralization

• The rxn of acid + base

• Example: H+ + OH- H20

• Neutral substances will not produce color changes in indicators.

• The negative ions of an acid combine with the positive ions of a base to produce an ionic compound called a salt.

• The neutralization reaction between acid and base produces a salt and water.

• (H3O+ + Cl-) + (Na+ + OH-) 2HOH + (Na+ + Cl-)

acid base water salt

Neutralization and Salts

Indicators

• Something that indicates the pH of a solution or substance

• Examples:– Natural (some flowers, cabbage juice, red

onion juice)– pH paper (Litmus blue or red, universal)