Ionization

Rucete ✏ Chemistry In a Nutshell

1. Ionization of Acids

• Ionization refers to the process in which an acid donates a proton (H⁺) and becomes its conjugate base.
• Example for a monoprotic acid (HA):

HA ⇌ H⁺ + A⁻

• The extent to which an acid ionizes depends on its acid strength:
• Strong acids: completely ionize
• Weak acids: partially ionize (establish equilibrium)

2. Acid Strength and Ionization Constant (Ka)

• The acid dissociation constant (Ka) quantifies how much an acid ionizes in solution.
• Higher Ka → stronger acid (more ionization)
• Lower Ka → weaker acid (less ionization)

Ka = [H⁺][A⁻]/[HA]

3. pKa and Relationship to Strength

• pKa = –log(Ka)
• Lower pKa = stronger acid
• Higher pKa = weaker acid

4. Buffers and Ionization

• Buffers consist of a weak acid and its conjugate base (or weak base and its conjugate acid).
• They resist changes in pH when small amounts of acid or base are added.

5. Henderson–Hasselbalch Equation

$$\text{pH}=\text{pKa}+\log \left(\frac{[{\text{A}}^{-}]}{[\text{HA}]}\right)$$
$$\text{pOH}=\text{pKb}+\log \left(\frac{[{\text{BH}}^{+}]}{[\text{B}]}\right)$$$$$$

• This equation helps calculate the pH of buffer solutions.