water

1. Salt Hydrolysis

2.  Hydrolysis is a term applied to reactions of
aquated ions that change the pH from 7
• When NaCl is placed in water, the resulting
solution is observed to be neutral (pH = 7)
• However when sodium acetate (NaC2H3O2) is
dissolved in water the resulting solution is basic
• Other salts behave similarly, NH4Cl and AlCl3
give acid solutions.
• These interactions between salts and water are
called hydrolysis

3. Hydrolysis of Salts
Salts can be acidic, basic, or neutral.
1. Neutral Salts
Consider NaCl
The neutralization equation used to produce NaCl will tell us what kind of salt it
is.

4. Hydrolysis of Salts
Salts can be acidic, basic, or neutral.
1. Neutral Salts
Consider NaCl
The neutralization equation used to produce NaCl will tell us what kind of salt it
is.
→ NaCl + HOH

5. Hydrolysis of Salts
Salts can be acidic, basic, or neutral.
1. Neutral Salts
Consider NaCl
The neutralization equation used to produce NaCl will tell us what kind of salt it
is.
H + OH → NaCl + HOH

6. Hydrolysis of Salts
Salts can be acidic, basic, or neutral.
1. Neutral Salts
Consider NaCl
The neutralization equation used to produce NaCl will tell us what kind of salt it
is.
HCl + NaOH → NaCl + HOH

7. Hydrolysis of Salts
Salts can be acidic, basic, or neutral.
1. Neutral Salts
Consider NaCl
The neutralization equation used to produce NaCl will tell us what kind of salt it
is.
HCl + NaOH → NaCl + HOH
strong acid strong base neutral salt

8. Hydrolysis of Salts
Salts can be acidic, basic, or neutral.
1. Neutral Salts
Consider NaCl
The neutralization equation used to produce NaCl will tell us what kind of salt it
is.
HCl + NaOH → NaCl + HOH
strong acid strong base neutral salt
When the acid and base parents are both strong the salt is always neutral.
-

9. A neutral salt will dissociate in water.
NaCl → Na+ + Cl-
Cross off the both ions that come from strong parents as they do not hydrolyze
or react further with water- they are neutral.
no ions to hydrolyze-
neutral

10. Hydrolysis of Salts
Salts can be acidic, basic, or neutral.
2. Basic Salts
Consider NaCN

11. Hydrolysis of Salts
Salts can be acidic, basic, or neutral.
2. Basic Salts
Consider NaCN
H + OH → NaCN + HOH

12. Hydrolysis of Salts
Salts can be acidic, basic, or neutral.
2. Basic Salts
Consider NaCN
HCN + NaOH → NaCN + HOH

13. Hydrolysis of Salts
Salts can be acidic, basic, or neutral.
2. Basic Salts
Consider NaCN
HCN + NaOH → NaCN + HOH
weak acid strong base basic salt

14. Hydrolysis of Salts
Salts can be acidic, basic, or neutral.
2. Basic Salts
Consider NaCN
HCN + NaOH → NaCN + HOH
weak acid strong base basic salt

15. A basic salt will first dissociate in water
NaCN → Na+ + CN-
Cross off the Na+ because it has a strong parent and does not hydrolyze- it is
neutral
Then the CN- ion, from the weak parent, will hydrolyze (react with water) as a
Bronsted base.
CN- + H2O ⇄ HCN + OH-
negative ion left- basic

16. Hydrolysis of Salts
Salts can be acidic, basic, or neutral.
3. Acidic Salts
Consider NH4Cl
→ NH4Cl

17. Hydrolysis of Salts
Salts can be acidic, basic, or neutral.
3. Acidic Salts
Consider NH4Cl
HCl + NH3 → NH4Cl

18. Hydrolysis of Salts
Salts can be acidic, basic, or neutral.
3. Acidic Salts
Consider NH4Cl
HCl + NH3 → NH4Cl
strong acid weak base acid salt

19. Hydrolysis of Salts
Salts can be acidic, basic, or neutral.
3. Acidic Salts
Consider NH4Cl
HCl + NH3 → NH4Cl
strong acid weak base acid salt

20. An acidic salt will first dissociate in water
NH4Cl → NH4
+ + Cl-
Cross off the Cl- because it has a strong parent and does not hydrolyze- it is
neutral
Then the NH4
+ ion, from the weak parent, will hydrolyze (react with water) as a
Bronsted acid.
NH4
+ + H2O ⇄ H3O+ + NH3
positive ion left- acidic

21. Summary
Acid-Base Properties of Salts
“Hydrolysis”

22. 22
Electrolytes and Nonelectrolytes

23. In water,
 strong electrolytes produce ions and
conduct an electric current
 weak electrolytes produce a few ions
 nonelectrolytes do not produce ions

24. Strong electrolytes
 dissociate in water, producing positive and
negative ions
 dissolved in water will conduct an electric
current
 in equations show the formation of ions in
aqueous (aq) solutions
H2O 100% ions
NaCl(s) Na+(aq) + Cl(aq)
H2O
CaBr2(s) Ca2+(aq) + 2Br(aq)

25. Complete each of the following equations for
strong electrolytes dissolving in water.
H2O
A. CaCl2 (s) ?
1) CaCl2(s) 2) Ca2+(aq) + Cl2
−(aq)
3) Ca2+(aq) + 2Cl−(aq)
H2O
B. K3PO4 (s) ?
1) 3K+(aq) + PO4
3−(aq) 2) K3PO4(s)
3) K3
+(aq) + P3−(aq) + O4
−(aq)

26. Complete each of the following equations for
strong electrolytes dissolving in water.
H2O
A. CaCl2 (s) ?
3) Ca2+(aq) + 2Cl−(aq)
H2O
B. K3PO4 (s) ?
1) 3K+(aq) + PO4
3−(aq)

27. A weak electrolyte
 dissociates only slightly in water
 in water forms a solution of a few ions and
mostly undissociated molecules
HF(g) + H2O(l) H3O+(aq) + F(aq)
NH3(g) + H2O(l) NH4
+(aq) + OH(aq)

28. Nonelectrolytes
 dissolve as
molecules in
water
 do not produce
ions in water
 do not conduct
an electric
current

30. An equivalent (Eq) is the amount of an
electrolyte or an ion that provides 1 mole of
electrical charge (+ or –).
1 mole Na+ = 1 Eq
1 mole Cl− = 1 Eq
1 mole Ca2+ = 2 Eq
1 mole Fe3+ = 3 Eq

32. In replacement solutions for
body
fluids, the electrolytes are given
in
milliequivalents/L (mEq/L).
Ringer’s Solution
Cations Anion_____
Na+ 147 mEq/L Cl− 155 mEq/L
K+ 4 mEq/L
Ca2+ 4 mEq/L
155 mEq/L = 155 mEq/L