Bases

Introduced to this in AP Chemistry

Refer to Acid-Base Theories if needed

Arrhenius Model §

Strong base

• Acids produce H${}^{+}$ in aqueous solution
• Bases produce OH${}^{-}$ in aqueous solution

Bronstead-Lowry Model §

Weak base

• Acids are H${}^{+}$ donors
• Bases are H${}^{+}$ acceptors

Dissociation of Strong Bases §

MOH${}_{(s)}$ $\to$ M${}_{aq}^{+}$ + OH${}_{aq}^{-}$

• Strong bases are metallic hydroxides
  • Group I hydroxides (NaOH, KOH) are very soluble
  • Group II hydroxides (Ca, Ba, Mg, Sr) are less soluble
• pH of strong bases is calculated directly from the concentration of the base in solution
  • 0.10 M NAOH = 0.10 M OH${}^{-}$
• Formula for Calcium Hydroxide: Ca(OH)${}_2$

Reaction of Weak Bases with Water §

The base reacts with water producing its conjugate acid and hydroxide ion:

CH${}_3$NH${}_2$ (aq) + H${}_2$O (l) $\leftrightarrow$ CH${}_3$NH${}_3^{+}$ (aq) OH${}^{-}$ (aq)

CH${}_3$NH${}_3^{+}$ - Conjugate Acid

OH${}^{-}$ - Hydroxide ion

K${}_b$ = 4.38 * 10${}^{-4}$ = $\frac{[C{H}_{3}N{H}_3^{+}][O{H}^{-}]}{[C{H}_{3}N{H}_2]}$

All weak bases do this - DO NOT try to make this complicated

Weak Base Equilibrium Problem §