dissociation constant

How is the strength of a weak acid or base explained

By its degree of ionisation at equilibrium in aqueous solution.

What is the general dissociation equation for a weak acid

HA(aq) + H₂O(l) ⇌ A⁻(aq) + H₃O⁺(aq).

What is the general dissociation equation for a weak base

B(aq) + H₂O(l) ⇌ BH⁺(aq) + OH⁻(aq).

What is the expression for Ka

Ka = [A⁻][H₃O⁺] / [HA].

What is the expression for Kb

Kb = [BH⁺][OH⁻] / [B].

What does a larger Ka or Kb value indicate

A stronger weak acid or base

What does a smaller Ka or Kb value indicate

A weaker acid or base, less ionisation, and lower conductivity.

What is the relationship between Ka and pKa

pKa = −log(Ka); smaller pKa means a stronger acid.

What is the relationship between Kb and pKb

pKb = −log(Kb); smaller pKb means a stronger base.

How are Ka and Kb for conjugate acid–base pairs related

Ka × Kb = Kw = 1 × 10⁻¹⁴.

What is the relationship between pKa and pKb

pKa + pKb = 14 at 25 °C.

Why is a strong acid’s conjugate base weak

Because the forward reaction is strongly favoured, leaving the conjugate base unable to react effectively.