Dissociation constant

In this episode of the 'Chemical Equilibrium' course, we explore the dissociation constant, a vital parameter that measures the extent to which a substance dissociates into its ions in solution. Building on previous discussions of equilibrium constants, acid-base equilibrium, and pH, this episode explains how dissociation constants, represented as Ka and Kb, help quantify the strength of acids and bases. We'll discuss how these constants vary with the nature of the solute and solution conditions, and their practical applications in chemistry and biology. By the end, you'll understand why dissociation constants are essential for predicting reaction behavior in aqueous solutions.

Check your understanding

These are the same multiple-choice questions you will see in the Quiz section after you listen to the episode. Use them here to preview or review the answers.

What does the dissociation constant (Ka or Kb) measure?

  1. The strength of intermolecular forces.
  2. The extent of dissociation of a substance into its ions.
  3. The solubility of a substance in water.
  4. The temperature at which a reaction occurs.
  5. The ability of a substance to form covalent bonds.
  6. The stability of a compound under pressure.

What is the relationship between Ka and pKa?

  1. pKa = -log(Ka).
  2. Ka = -log(pKa).
  3. Ka and pKa are unrelated.
  4. Higher Ka means higher pKa.
  5. Lower Ka means stronger acid.
  6. Higher Ka means lower pKa.

What is an example of a weak acid with its Ka value?

  1. HCl, Ka = 1 × 10⁻³.
  2. H₂SO₄, Ka = 1 × 10⁻¹.
  3. CH₃COOH, Ka = 1.8 × 10⁻⁵.
  4. HNO₃, Ka = 1 × 10³.
  5. NH₃, Ka = 1 × 10⁻¹⁴.
  6. H₂CO₃, Ka = 4.3 × 10⁻⁷.

How does temperature affect the dissociation constant?

  1. Ka and Kb remain constant regardless of temperature.
  2. Ka and Kb increase with temperature for all reactions.
  3. Ka and Kb may increase for endothermic dissociation reactions.
  4. Temperature has no effect on weak acids and bases.
  5. Ka and Kb decrease with temperature for exothermic reactions.
  6. Temperature stabilizes strong acids but not weak ones.

What is a key application of dissociation constants in chemistry?

  1. Predicting boiling points.
  2. Designing buffer solutions.
  3. Calculating molecular weight.
  4. Determining reaction kinetics.
  5. Performing acid-base titrations.
  6. Calculating the rate of nuclear decay.

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