MODULE 9 - ACIDS, BASES, & SALTS

Learning Outcomes

  • Define key terms: acids, bases, salts, neutralization, hydrolysis.

  • Describe properties of acids, bases, and salts.

  • Compare and contrast definitions from Arrhenius, Bronsted-Lowry, and Lewis theories.

  • Convert hydrogen-ion concentrations into pH values.

  • Convert hydroxide-ion concentrations into pOH values.

Definitions

Acids

  • Chemical species that donate protons (H+) or accept electrons.

  • Common in food: lemon juice (pH 2.00-2.60), grapes (2.90-3.82).

Bases

  • Chemical species that donate electrons, accept protons, or release OH- ions.

  • High pH in vegetables: cabbage (5.50-6.75), cauliflower (5.50-7.50).

Salts

  • Ionic compounds formed from neutralization reactions between acids and bases.

  • Consist of cations and anions.

Properties

Properties of Acids

  • Sour taste.

  • Corrosive to metals.

  • Change litmus paper to red.

  • Conduct electricity in solution.

  • pH less than 7.

Properties of Bases

  • Bitter taste.

  • Slippery in water.

  • Change litmus to blue.

  • Conduct electricity in solution.

  • pH more than 7.

Properties of Salts

  • Salty taste.

  • Crystallizes in cubes.

  • Soluble in water, slight solubility in alcohol.

Reactions

Neutralization Reaction

  • Reaction of an acid with a base producing water and salt.

  • Example: HCl + NaOH → H2O + NaCl.

Strong vs Weak Acids and Bases

  • Strong Acids: Fully dissociate in water (e.g., HCl, H2SO4).

  • Weak Acids: Partially dissociate (e.g., HCOOH, H2SO3).

  • Strong Bases: Fully dissociate (e.g., NaOH, KOH).

  • Weak Bases: Partially dissociate (e.g., NH3).

Measurement of Acidity and Basicity

  • Acidity and basicity measured using pH and pOH.

  • Formulas:

    • pH = -log[H+]

    • pOH = -log[OH-]

    • pH + pOH = 14.

Examples of Calculations

  • Sodium Hydroxide: Given [OH-] = 3 x 10-2 M. Calculate pH, pOH, [H+].

  • Hydrochloric Acid: Given pH = 1.8, calculate pOH and concentrations.

  • Formic Acid: Given [H+] = 0.15 M, calculate pOH.

Salt Hydrolysis

  • A salt ion reacts with water, producing acidic or basic solutions.

  • Acidic from strong acids and weak bases; Basic from weak acids and strong bases.