2) The negatively charged electrons of the oxygen atom are attracted to the
positively charged proton.
- Other examples:
H O+ H O H
Acid
+
H
−O H H +
H
O H
Base
COH H
O
CO−
O
Acid
+ O H + O+ H
H
H 3 C H 3 C
H
Base
COH
O
CO−
O
H
Acid
H 3 C + −O H H 3 C + O H
Base
3.5 THE STRENGTH OF ACIDS AND BASES: Ka AND pKa
- In a 0.1 M solution of acetic acid at 25 °C only 1% of the acetic acid molecules
ionize by transferring their protons to water.
COH + +
O
H 3 CC−
O
H 2 OHH 3 C O 3 O+
3.5A THE ACIDITY CONSTANT, Ka
- An aqueous solution of acetic acid is an equilibrium:
Keq = [H[CHOCO]^ [CHH] [HCOO]]
3 2 2
3 3 2 −
- The acidity constant:
- For dilute aqueous solution: water concentration is essentially constant (~ 55.5
M)
