2.
Salt Hydrolysis: reaction of the anions or
cations in a salt with water to form an
acidic or basic solution.
3. Salt + water = ?
1. Neutral solution
2. Basic solution
3. Acidic solution
4. Salt + water = ?
1. Neutral solution:
Conjugate of strong Acid + conjugate of strong Base neutral solution
•Things to consider:
–Metal hydroxides of group I and II except Be are strong bases
–All other metal hydroxides are weak bases
5. Salt + water = ?
1. Neutral solution:
2. Basic solution:
Conj. of weak acid + Conj. of strong base basic solution
6.
Sodium Ethanoate
(CH3COONa)
› The salt of a weak acid
(CH3COOH) and a strong base
(NaOH)
› Completely ionizes in solution:
CH3COONa CH3COO- + Na+
› CH3COO- acts as a base
Will take H+ from water!
CH3COO- + H2O
OH-
CH3COOH +
Why is the resulting solution
basic?
7. Salt + water = ?
1. Neutral solution:
2. Basic solution:
3. Acidic solution:
Conj. of weak base + Conj. of strong acid acidic solution
8.
Ammonium Chloride (NH4Cl)
› NH4Cl is the salt of a strong acid (HCl) and a
weak base (NH3)
› Completely ionizes in solution:
NH4Cl NH4+ + Cl› NH4+ acts as an acid in water
NH4+ + H2O
H3O+ + NH3
Why is the resulting solution acidic?
9.
Determine if the following aqueous
solutions will be acidic, basic or neutral:
› NH4NO3
› KCl
› NaHCO3
› Na2SO3
10. When the negative ion is from a weak
acid then the salt is basic by hydrolysis
When the positive ion is from a weak
base then the salt is acidic by hydrolysis
If the salt is formed from a strong acid
and strong base then it is neutral
If the salt is formed from a weak acid
and weak base then its hydrolysis is
determined by the relative Ka and Kb
values
11.
This effect is typified in aluminium salts
(the aluminium ion has a charge of 3+)
which are very acidic in solution.
Notas del editor
NH4NO3 acidic because NH4 is a weak acid that can interact with water!KCl neutral because the salt is made from a strong acid and baseNaHCO3 is basic because HCO3- can act as a weak baseNa2SO3 is basic because SO32- can act as a weak base