Chapter 17Acid-Base Equilibria

Brønsted-Lowry Acids

HNO3 + H2O → H3O+ + NO3-

Acid

Brønsted-Lowry Bases

+ -( aq) ( l) ( aq) ( aq)3 2 4

BaseNH +H O →NH +OH

Base

Arrhenius

Acids and Bases

NH3+ H2O → NH4+ + OH-

HCl + H2O → H3O+ + Cl-

Acids and Bases

LewisBH3 + NH3 → BH3NH3

Acid Base

BH H

HN H

H

H

: B N H

H

H

H

H

H

Examples of Lewis Acid and Bases

Acid Base

Conjugate Acid-Base Pairs

Conjugate Acid-Base Pairs

Multiprotic acids

A B

A B

Multiprotic acids

Ionization Constants for Acids

Ionization Constants for Bases

] + -

- +2 b( aq) K( aq) ( l) ( l)+

[HB ][OHB +H O OH HB =

[B]

Molecular basis of acid/base strength

Increasing acid strength

HF HCl HBr HI

H–A bond strength (kJ/mol) 569 431 368 297

Electron affinity of A (kJ/mol) 328 349 325 295

Electron affinity

Cl O H Cl O HO+-

Cl O HO

O-

Cl O HO

O

O-

-

--

2+3+

:..

::..

..

..:

..

..

..

..

..

..:

..

..

..

..

..

..:

..

..

....

..

..::

::

hypochlorous acid chlorous acid chloric acid perchloric acid

Summary

3.2 × 10 5

Concepts from Chapter 17

Definitions of acids and bases (Lewis, Brønsted and Arrhenius)

Conjugate acid-base pairs

Ionization constants (Ka, Kb, Kw) and ionization constant expressions

pH, pOH, pKw,

Factors contributing to acidity

Solvent leveling

The strong acids and strong bases (names and formulæ)

Acid-base reactions (strong-strong, strong-weak, weak-strong, and weak-weak)

Calculations

Method of iterative approximation