Summary of Titration Process

Titration of Benzoic Acid with Lithium Hydroxide

Reaction Details

  • Benzoic Acid (C6H5COOH)
    • Concentration: 1.00 M
    • Volume: 75.0 mL
  • Lithium Hydroxide (LiOH)
    • Concentration: 0.50 M
  • Ka of Benzoic Acid: 6.30 x 10^-5

Key Questions

a. Net Ionic Equation
  • Reaction:
    • C6H5COOH (aq) + LiOH (aq) → C6H5COO^-Li^+ (aq) + H2O (l)
b. Initial pH Before Titration
  • Formula Used: pH = -log[H^+]
  • Initial Concentration of Benzoic Acid: 1.00 M (before any reaction with LiOH)
  • Calculation:
    • [H+] = √(Ka × [C6H5COOH]) = √(6.30 x 10^-5 × 1.00)
    • pH ≈ 4.20
c. pH at Half-Way to Equivalence Point
  • At Halfway Point: [C6H5COOH] = [C6H5COO^-]
  • pH:
    • pH = pKa = -log(6.30 x 10^-5) ≈ 4.20
d. pH at Equivalence Point
  • At Equivalence Point: The solution contains lithium benzoate, a weak base.
  • K_b Calculation:
    • Kb = Kw / Ka = 1.00 x 10^-14 / 6.30 x 10^-5
    • Find [OH^-] using K_b and then convert to pH.
  • Estimated pH: Approximately 9.25 (requires calculation).
e. Titration Curve
  • Sketch Required: Show a rising curve that levels off after the equivalence point, indicating pH change through titration.
f. Concentration at pH 3.42
  • Comparison: At pH 3.42,
      • [H+] = 3.79 x 10^-4 M relates to benzoic acid which remains in solution.
    • Since the solution is still acidic (pH < pKa), benzoic acid concentration is higher than that of lithium benzoate.
  • Conclusion: Benzoic Acid has a higher concentration than lithium benzoate or lithium hydroxide at pH 3.42 due to its weak acidic nature and the dissociation equilibrium.