Chapter 18: Acids, Bases, and Salts

Strong Acid

An acid that completely ionizes in aqueous solution, producing a high concentration of H⁺ ions.

Weak Acid

An acid that only partially ionizes in aqueous solution, producing a lower concentration of H⁺ ions.

Strong Base

A base that completely dissociates in aqueous solution, releasing a high concentration of OH⁻ ions.

Weak Base

A base that only partially dissociates in aqueous solution, releasing fewer OH⁻ ions.

pH

A scale that measures the acidity or basicity of a solution based on the concentration of H⁺ ions, ranging from 0 (acidic) to 14 (basic), with 7 being neutral.

Factors Affecting Acid and Base Strength

• Degree of ionization or dissociation in water.
• Bond strength between hydrogen and the acid molecule.
• Stability of the conjugate base after ionization.

Measuring pH

pH Formula

$\mathrm{pH}=-log\left(\mathrm{[H⁺]}\right)$

pH Indicators

• Litmus paper: Turns red for acids and blue for bases.
• Universal indicator: Changes color based on pH range.
• pH meter: Provides precise pH measurements electronically.

Examples of Acids and Bases

Strong Acids

Examples include HCl, H₂SO₄, and HNO₃.

Weak Acids

Examples include CH₃COOH and HF.

Strong Bases

Examples include NaOH and KOH.

Weak Bases

Examples include NH₃ and C₆H₅NH₂.

Questions for Students

1. Define strong and weak acids. How do they differ in terms of ionization?
2. What factors determine the strength of an acid or base?
3. Write the formula for calculating pH and explain its significance.
4. Give examples of strong and weak acids and bases. How do their properties differ?
5. How does the pH scale help identify acidic, basic, and neutral solutions?