AP CHEM Acids + Bases

Q1. A weak diprotic acid H₂A undergoes two dissociations. Which of the following correctly compares Ka1 and Ka2?

Ka1 > Ka2 because removing a proton from a negatively charged ion is harder

If the Ka of a weak acid increases, what happens to the Kb of its conjugate base?

Kb decreases because Ka and Kb are inversely related

Which of the following acids is the strongest?

Ka = 1.0 × 10⁻²

Two acids, HA and HB, are dissolved in water. HA has a pH of 2.5 and HB has a pH of 4.0 at the same concentration. Which of the following is true?

HA is stronger because it has a lower pH, meaning more H⁺ ions in solution

During a strong base / weak acid titration, what is true at the half-equivalence point?

pH = pKa of the weak acid

In a strong base / weak acid titration, a student adds base beyond the half-equivalence point but before the equivalence point. Which of the following best describes the solution?

[A⁻] > [HA] and pH > pKa

Consider the equilibrium: HA ⇌ H⁺ + A⁻. If NaA (a soluble salt that dissociates into Na⁺ and A⁻) is added to the solution, which of the following will occur?

The reaction shifts left, consuming H⁺ and increasing pH

Consider the equilibrium: HA ⇌ H⁺ + A⁻. A small amount of HCl is added. What happens?

Equilibrium shifts left to consume the excess H⁺

. The second dissociation of H₂SO₃ is represented as: HSO₃⁻ ⇌ H⁺ + SO₃²⁻. Compared to the first dissociation of H₂SO₃, this reaction has a:

Smaller Ka because it is harder to remove a proton from a negatively charged species