Acid/Base Chemistry Part II

CHEM 2124 – General Chemistry II

Alfred State College

Professor Bensley

Learning Objectives

• Write the chemical equation for a weak acid undergoing acid ionization in aqueous solution.

• Define acid dissociation constant.• Determine Ka from a solution pH.• Calculate concentrations of species in

a weak acid solution using Ka.• Write the hydrolysis reaction of an ion

to form an acidic solution.

Learning Objectives

• Recognize common acid-base reactions.

• Predict whether a salt solution is acidic, basic, or neutral.

• Calculate concentrations of acid or base solutions through titrations.

• Define buffer.

Learning Objectives

• Describe the pH change of a buffer solution with the addition of an acid or a base.

• Calculate the pH of a buffer from given volumes of solution.

• Calculate the pH of a buffer when a strong acid or a strong base is added.

• Learn and apply the Henderson-Hasselbalch equation.

Acid/Base Chemistry – Part II

A. Equilibrium and Acid Dissociation Constants

B. The relationship between [H3O+], pH, and Ka

[H3O+] = √KaC0

pH = ½ pKa – ½ log C0

Acid/Base Chemistry – Part II

Acid/Base Chemistry – Part II

1. Neutralization reaction

C. Common Acid/Base Reactions

2. Net Ionic Reaction of Neutralization reactions:

3. Bicarbonate Base reactions

D. The Acidity and Basicity of Salt Solutions

NaCl

Na+

from NaOHstrong base

Cl−

from HClstrong acid

NaHCO3

Na+

from NaOHstrong base

HCO3−

from H2CO3

weak acid

NH4Cl

NH4+

from NH3

weak base

Cl−

from HClstrong acid

E. Buffers

A buffer is a solution whose pH changes very littlewhen acid or base is added.

Acid/Base Chemistry – Part II

Acid/Base Chemistry – Part II

F. Calculating the pH of a Buffer

Henderson-Hasselbalch Equation

pH = pKa + log ([A-]/[HA])

pH = pKa + log Cs – log Ca