Bases, Neutralization, & Buffers

Bases Water solutions are slippery – bitter Litmus dye: red → blue Some dissolve fats (soap)

Arrhenius Definition Base – releases OH - ion in water

Bronsted-Lowry Definition Base – proton acceptor (H + )

Strength of Bases Strong Bases – Ionize all the way –NaOH –KOH Weak bases – Only ionize a little –NH 3 (ammonia) –Ca(OH) 2 Water can be either a weak base or a weak acid H 2 O + H 2 O ↔ H 3 O + + OH - Can damage tissue If concentrated

Use of a Weak Acid Ca(OH) 2 is added to seawater (or better, Great Salt Lake water) (Magcorp) The magnesium in the water reacts with the OH- ion and forms Mg(OH) 2 which precipitates out (not very soluble) Collect the Mg(OH) 2 solid and acidify which produces a concentrated Mg 2+ solution Recover pure Mg by electrolysis

Neutralization For strong acids and bases and some others –Acid + base = salt + water HCl + H 2 O → H + + Cl - + H 2 O NaOH + H 2 O → Na + + OH - + H 2 O

Use of salts How do they make salt and vinegar potato chips? –If you react NaOH with vinegar (acetic acid, HAc) what do you get? –The sodium salt of acetic acid – sodium acetate is sprinkled on chips –What happens to the NaAc when it hits the water in your mouth? (remember acetic acid is a weak acid)

Buffers Systems that minimize changes in pH –As in blood Weak acid with a salt of the weak acid Weak base with a salt of the weak base

H27 – C11 21, , 61, , 76, 77, 80