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