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pH of Weak Acids quiz #1 Flashcards

pH of Weak Acids quiz #1
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  • Would the pH at the equivalence point be acidic when titrating a weak acid with a strong base?
    Yes, the pH at the equivalence point will be greater than 7 (basic) when titrating a weak acid with a strong base, because the conjugate base of the weak acid is present and partially hydrolyzes to produce OH⁻ ions.
  • What is the pH of a 0.400 M solution of HF (Ka = 6.8 × 10⁻⁴)?
    To find the pH, set up an ICE chart for HF: HF ⇌ H⁺ + F⁻. Let x be the concentration of H⁺ at equilibrium. Ka = x² / (0.400 - x) ≈ x² / 0.400. Solve for x: x² = (6.8 × 10⁻⁴)(0.400) = 2.72 × 10⁻⁴, so x = √(2.72 × 10⁻⁴) ≈ 0.0165 M. pH = -log(0.0165) ≈ 1.78.
  • What does the acronym ICE stand for when analyzing weak acid equilibria?
    ICE stands for Initial, Change, Equilibrium, and is used to organize concentration changes during weak acid dissociation.
  • Why do weak acids require the use of an ICE chart for calculations?
    Weak acids only partially dissociate, so an ICE chart helps track the changes in concentrations to determine equilibrium values.
  • What unit is typically used for concentrations in an ICE chart for weak acids?
    Molarity (M) is the standard unit used for concentrations in an ICE chart for weak acids.
  • What constant is used to describe the dissociation of a weak acid?
    The acid dissociation constant, Ka, is used to quantify the extent of weak acid dissociation.
  • How does the percent ionization of a weak acid compare to that of a strong acid?
    The percent ionization of a weak acid is less than 100%, while a strong acid ionizes completely at 100%.
  • What information do you need to calculate the percent ionization of a weak acid?
    You need the equilibrium concentration of H3O+ and the initial concentration of the weak acid.
  • How can you determine the equilibrium concentration of hydronium ion for a weak acid?
    You can either be given the value or calculate it using an ICE chart based on the initial conditions and Ka.
  • What does percent ionization indicate about a weak acid in solution?
    Percent ionization shows the fraction of acid molecules that have ionized in solution, reflecting the acid's strength.