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Determining Predominate Species quiz #1

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  • How do you determine whether the conjugate acid or conjugate base of a molecule is the predominant species in solution?
    Compare the solution pH to the molecule's pKa: if pH < pKa, the conjugate acid (protonated form) predominates; if pH > pKa, the conjugate base (deprotonated form) predominates; if pH = pKa, both forms are present in equal concentrations.
  • What does the Henderson-Hasselbalch equation reveal about the relative concentrations of conjugate acid and base?
    The Henderson-Hasselbalch equation (pH = pKa + log[conjugate base]/[conjugate acid]) shows the ratio of conjugate base to conjugate acid, allowing you to determine which species is more abundant at a given pH.
  • What is the predominant species when the pH of a solution is equal to the pKa of an acid?
    When pH equals pKa, the concentrations of conjugate acid and conjugate base are equal, so neither species predominates; both are present at 50%.
  • If the pH of a solution is lower than the pKa of an acid, which form of the molecule is most abundant?
    The conjugate acid (protonated form) is most abundant when the pH is lower than the pKa.
  • If the pH of a solution is higher than the pKa of an acid, which form of the molecule is most abundant?
    The conjugate base (deprotonated form) is most abundant when the pH is higher than the pKa.
  • How do you determine which form (conjugate acid or conjugate base) of a molecule is predominant in solution?
    Compare the solution pH to the molecule's pKa: if pH < pKa, the conjugate acid predominates; if pH > pKa, the conjugate base predominates.
  • What does the Henderson-Hasselbalch equation tell you about the concentrations of conjugate acid and base?
    It shows the ratio of conjugate base to conjugate acid, allowing you to determine which species is more abundant at a given pH.
  • What is true about the concentrations of conjugate acid and base when pH equals pKa?
    When pH equals pKa, the concentrations of conjugate acid and conjugate base are equal, so neither species predominates.
  • Which form of a molecule is most abundant when the pH is lower than the pKa?
    The conjugate acid (protonated form) is most abundant when the pH is lower than the pKa.
  • Which form of a molecule is most abundant when the pH is higher than the pKa?
    The conjugate base (deprotonated form) is most abundant when the pH is higher than the pKa.