# IV.13. HYDROLYSIS (Hebden p. 144 – 148).

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IV.13. HYDROLYSIS (Hebden p. 144 – 148)

Hydrolysis of a Salt Rx between water and cation &/or anion in salt that produces an acidic or basic solution All salts are 100% ionized in water

Spectator Ions Do NOT react with water
The conjugates of STRONG acids and bases

Spectator Cations Alkali metals Alkaline earth metals
Ex: NaOH  Na+ + OH-

Spectator Anions 1st top of Acid/ Base Table (not HSO4- b/c it is a weak acid) Ex: HCl  H+ + Cl-

To determine the behavior of salt in water…
Determine ions Discard spectators Remaining ions are acids if on acid side of table or bases if on base side of table

Ex #1: NaCl Na+ + Cl- Both Na+ and Cl- are spectators
Therefore, solution is NEUTRAL

2. NH4Cl  NH4+ + Cl- Cl- is a spectator Solution is acidic
NH4+ + H2O = H3O+ + NH3

3. NaF  Na+ + F- Na+ is a spectator Solution is basic
F- + H20 = HF + OH-

4. NaHC2O4  Na++HC2O4- Na+ is a spectator Solution either acidic or basic b/c HC2O4- is amphiprotic We must determine which rx is predominant

Ka for HC2O4- = 6.4 x 10-5 Kb = Kw /Ka = 1.00 x / 5.9 x 10-2 = 1.7 x 10-13 Ka > Kb so solution is acidic HC2O4- + H20 = H3O+ +C2O42-

Must determine predominant rx
5. NH4NO2  NH4+ + NO2- No spectators Must determine predominant rx

Ka of NH4+ = 5.6 x 10-10 Kb of NO2- = Kw/Ka = 1.0 x / 4.6 x 10-4 = 2.2 x 10-11 Solution is acidic NH4+ + H20 = H3O+ + NH3

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