Strong Acids and Strong Bases

Definition and Properties

Strong acids and strong bases are substances that completely ionize in water, producing high concentrations of hydronium ions (H+) or hydroxide ions (OH-), respectively. This complete ionization allows for straightforward calculations of pH and pOH in aqueous solutions.

• Strong acids: Substances that donate protons (H+) completely in water.

• Strong bases: Substances that accept protons or release hydroxide ions (OH-) completely in water.

Key Point: For strong acids and bases, the concentration of the acid or base equals the concentration of H+ or OH- ions, respectively.

Examples of Strong Acids and Bases

• Strong Acids: HCl, HBr, HI, HNO3, H2SO4, HClO4

• Strong Bases: NaOH, KOH, LiOH, Ca(OH)2, Ba(OH)2

Ionization and Concentration Calculations

When strong acids or bases dissolve in water, they dissociate completely. For example:

• HCl → H+ + Cl-

• NaOH → Na+ + OH-

For polyprotic acids or bases (e.g., Ba(OH)2), the number of ions produced depends on the formula:

• Ba(OH)2 → Ba2+ + 2OH-

pH and pOH Calculations

Formulas

• pH:

• pOH:

• Relationship: (at 25°C)

Calculation Steps

1. Identify the concentration of the strong acid or base.

2. For bases like Ba(OH)2, multiply the concentration by the number of OH- ions produced per formula unit.

3. Apply the pH or pOH formula using the calculated ion concentration.

Example Calculation

Example: If the concentration of Ba(OH)2 solution is 0.398 M, calculate its pOH.

• Ba(OH)2 dissociates to produce 2 moles of OH- per mole.

• OH- concentration:

• pOH calculation:

• pOH ≈ 0.10

Practice Problems

• Find the molar concentration of HBrO3 solution with a pH of 4.34:

• Calculate the pH of 25 mL of 5.45 × 10-4 M LiOH solution:

• HI is a strong acid (Ka = 3.2 × 109). Calculate [H+], [OH-], pH, and pOH of a 7.1 × 10-4 M HI solution:

Common Ions of Strong Bases

Calculation of pH or pOH

• For strong bases, use the concentration of the base to determine [OH-].

• For bases that release more than one OH- per formula unit, multiply accordingly.

Summary Table: Strong Acid and Base Calculations

Additional info: The notes infer standard GOB Chemistry content on strong acids/bases and pH/pOH calculations, including examples and formulas, to provide a complete study guide.