1. Acid – Base Theory

2. Definitions:
Arrhenius:
An acid is a substance that increases the H+ (or H3O+) concentration in an aqueous solution.
HCl + H 2O  H3O+ + Cl-
HCl  H+ + Cl-
A base is a substance that increases the OH- concentration
in an aqueous solution.
NaOH(s)  Na+ + OH-
What about Na2CO3 ????

3. Bronsted-Lowry:
HCl(aq) + NaOH(aq) → HOH + NaCl
Acid = a proton donor in a RXN
Base = a proton acceptor in a RXN

4. H+ .. H:O:H .. .. :O:H- .. Lewis: An acid is an electron pair acceptor
A base is an electron pair donor
water ..
:O:H- ..

5. Produce water and a salt (and sometimes carbon dioxide).
Acid/Base reactions:
Produce water and a salt (and sometimes carbon dioxide).
Hint: concentrate on the water first. Remember, water has the formula HOH.
Complete and balance the following:
HCl + KOH 
HOH KCl
HCl Ca(OH)2  2
2HOH CaCl2
Require equal numbers

6. 1. Ba(OH)2 + H3PO4  2. HC2H3O2 + NaOH  3. H2SO4 + KOH 
Try completing and balancing the following reactions.
The answers are on the next slide.
Ba(OH) H3PO4 
HC2H3O NaOH 
H2SO KOH 
H2CO NaOH 
5. Na2CO HCl 

7. 1. 3Ba(OH)2 + 2H3PO4  6H2O + Ba3(PO4)2
HC2H3O NaOH  H2O NaC2H3O2
H2SO KOH  2H2O K2SO4
4. H2CO NaOH  2H2O + Na2CO3
decomposition
5. Na2CO HCl  2NaCl + H2CO3 → 2NaCl + H2O + CO2(g)

8. NH4OH H2SO4 
NH HCl 
Give a definition of an acid:
An acid is a proton donor (H+)
Give a definition of a base:
A base is a proton acceptor

9. Na2CO3 + 2HCl  H2O + CO2(g) + 2NaCl
Conjugate acids and Conjugate bases
HCl + KOH 
HOH KCl
acid
base
conj. acid
conj. base
Na2CO HCl  H2CO NaCl
base
acid
conj. acid
conj. base
Na2CO HCl  H2O + CO2(g) + 2NaCl
acid
base
conj. acid
conj. base

10. NH HCl  NH Cl-

11. What is a strong Acid? Strong Acids:
An Acid that is 100% ionized in water.
Strong Acids:
100% ionized (completely dissociated) in water.
HCl + H2O  H3O+ + Cl-
often written as:
HCl  H+ + Cl-

12. 100% ionized (completely dissociated) in water. HCl + H2O  H3O+ + Cl-
Strong Acids:
100% ionized (completely dissociated) in water.
HCl + H2O  H3O+ + Cl-
Strong Acids:
Perchloric HClO4
Chloric, HClO3
Hydrobromic, HBr
Hydrochloric, HCl
Hydroiodic, HI
Nitric, HNO3
Sulfuric, H2SO4

13. What is a strong Base? NaOH(s)  Na+ + OH-
A base that is completely dissociated in water (highly soluble).
NaOH(s)  Na+ + OH-
Strong Bases:
Group 1A metal hydroxides
(LiOH, NaOH, KOH,
RbOH, CsOH)
Heavy Group 2A metal hydroxides
[Ca(OH)2, Sr(OH)2, and
Ba(OH)2]

14. Weak Acids: “The Rest”

15. Strong Acids:
100% ionized (completely dissociated) in water.
HCl + H2O  H3O+ + Cl-
Note the “one way arrow”.
Weak Acids:
Only a small % (dissociated) in water.
HC2H3O2 + H2O  H3O+ + C2H3O2-
Note the “2-way” arrow.
Why are they different?

16. Strong Acids:
HCl HCl
HCl
(H2O)
ADD WATER to MOLECULAR ACID

17. Strong Acids:
Cl-
H3O+
(H2O)
Cl-
H3O+
H3O+
Cl-
H3O+
Cl-
H3O+
Cl-
Note: No HCl molecules remain in solution, all have been ionized in water.

18. Weak Acid Ionization:
HC2H3O2
HC2H3O2
(H2O)
HC2H3O2
HC2H3O2 
HC2H3O2
Add water to MOLECULES of WEAK Acid

19. This gives rise to an Equilbrium expression, Ka
Weak Acid Ionization:
HC2H3O2
HC2H3O2
H C2H3O2-
HC2H3O2
(H2O)
HC2H3O2 
H C2H3O2-
HC2H3O2
HC2H3O2
Note: At any given time only a small portion of the acid molecules are ionized and since reactions are running in BOTH directions the mixture composition stays the same.
This gives rise to an Equilbrium expression, Ka