Acid/Base Chemistry Part I

CHEM 2124 – General Chemistry II

Alfred State College

Professor Bensley

Learning Objectives

Define acid and base according to the Arrhenius concept.

Define acid and base according to the Brønsted–Lowry concept.

Define the term conjugate acid-base pair. Identify acid and base species. Define amphiprotic species. Understand the relationship between the

strength of an acid and that of its conjugate base.

Learning Objectives

Decide whether reactants or products are favored in an acid-base reaction.

Define the ion-product constant for water. Calculate the concentrations of H3O+ and OH-

in solutions of strong acids or bases. Define pH and calculate the pH from

hydronium-ion concentrations. Calculate the hydronium-ion concentration

from pH.

Opener

Introduction to Acids and Bases

A. Arrhenius Definition

B. The Brønsted–Lowry Definition

Acid/Base Chemistry

H A + B A − H B++

gain of H+

acid base conjugatebase

conjugateacid

loss of H+

C. Proton Transfer Reactions

Acid/Base Chemistry

When a covalent acid dissolves in water, the proton transfer that forms H3O+ is called dissociation.

D. Relating Acid and Base Strength

A strong acid, HCl, is completely dissociated

into H3O+(aq) and Cl−(aq).

A weak acid containsmostly undissociatedacid, CH3COOH.

Acid and Base StrengthRelating Acid and Base Strength

A strong base, NaOH, is completely dissociated

into Na+(aq) and −OH(aq).

A weak base containsmostly undissociatedbase, NH3.

Acid/Base Chemistry

A Brønsted–Lowry acid–base reaction represents an equilibrium.

H A + B A − H B++acid base conjugate

baseconjugate

acid

E. Acid/Base Equilibrium

H A + B A − H B++stronger

acidstronger

baseweaker

baseweaker

acid

Acid/Base Chemistry

H O H

base

H O H

H +

conjugate acid

H O H

acid conjugate base

HO−

+ +

loss of H+

gain of H+

F. Dissocciation of Water

Kw =

Acid/Base Chemistry

pH = −log [H3O+]

F. Calculating pH

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Focus on the Human BodyThe pH of Body Fluids