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– NH3 (ammonia)– Ca(OH)2

• Water can be either a weak base or a weak acid

H2O + H2O ↔ H3O+ + OH-

Can damage tissueIf 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 Mg2+ solution

• Recover pure Mg by electrolysis

Neutralization

• For strong acids and bases and some others– Acid + base = salt + water

HCl + H2O → H+ + Cl- + H2O

NaOH + H2O → Na+ + OH- + H2O

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, 34 - 36, 61, 64 - 69, 76, 77, 80