Ka, pKa and weak acid pH

Ka, pKa and weak acid pH Quiz

Edexcel A-Level Chemistry: Quiz

Studying this course? Keep your progress in one place.

Pick an answer for each. Quizzes never use energy.

5 questions, one answer each

Each answer is checked as you go, with why.

See all 5 questions

  1. 1. A weak acid HA has KaK_a = 4.0 × 10⁻⁶ mol dm⁻³. What is its pKₐ to 2 d.p.?

    • A. 5.40
    • B. 6.00
    • C. 5.60
    • D. −5.40

  2. 2. What is the pH of 0.0200 mol dm⁻³ HA with KaK_a = 5.0 × 10⁻⁶ mol dm⁻³?

    • A. 1.70
    • B. 3.50
    • C. 2.20
    • D. 4.00

  3. 3. Which assumption is NOT used when calculating the pH of a weak acid?

    • A. [H+]=[A−][H^+]=[A^-]
    • B. The equilibrium [HA] is about its initial value
    • C. Water's ionisation is negligible
    • D. The acid is fully dissociated

  4. 4. Acid X has pKₐ 3.2 and acid Y has pKₐ 4.8, both at the same concentration. Which is correct?

    • A. Y is stronger with a larger KaK_a
    • B. X has the larger KaK_a and is stronger
    • C. They have the same KaK_a
    • D. X has the smaller KaK_a

  5. 5. In a titration of a weak acid with NaOH, the pH at half the equivalence volume is 4.76. What is KaK_a?

    • A. 4.76 mol dm⁻³
    • B. 1.74 × 10⁻⁵ mol dm⁻³
    • C. 5.75 × 10⁻⁴ mol dm⁻³
    • D. 1.74 × 10⁻⁹ mol dm⁻³

Quiz