IV.13. HYDROLYSIS (Hebden p. 144 – 148). Hydrolysis of a Salt Rx between water and cation &/or...
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Transcript of IV.13. HYDROLYSIS (Hebden p. 144 – 148). Hydrolysis of a Salt Rx between water and cation &/or...
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 5 @ 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 10-14 / 5.9 x 10-2
= 1.7 x 10-13
Ka > Kb so solution is acidic
HC2O4- + H20 = H3O+ +C2O4
2-
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 10-14 / 4.6 x 10-4
= 2.2 x 10-11
Solution is acidic NH4
+ + H20 = H3O+ + NH3