Free Powerpoint Presentations

Acids and Bases
Page
2

DOWNLOAD

PREVIEW

Slide 10

Monoprotic acid: One acidic proton (HCl)

Monoprotic acid: One acidic proton (HCl)

HCl(aq) H+(aq) + Cl-(aq)

Diprotic acid: Two acidic protons (H2SO4)

H2SO4(aq) H+(aq) + HSO4-(aq)

HSO4- (aq) H+(aq) + SO4 2-(aq)

Oxyacids: Acidic proton is attached to an oxygen atom (H2SO4)

Organic acids: Those with a carbon atom backbone, contain the carboxyl group (-COOH). CH3-COOH, C6H5-COOH

Slide 11

Water as an Acid and a Base

Water as an Acid and a Base

A substance is said to be amphoteric if it can behave either as an acid or as a base. Water is amphoteric (it can behave either as an acid or a base).

H2O + H2O  H3O+ + OH

conj conj

acid 1 base 2 acid 2 base 1

Kw = [H3O+][OH-] = [H+][OH-] = 1  1014 at 25C

Where, Kw is the ion-product constant or dissociation constant for water.

[H+] = [OH-] = 1.0 x 10-7 M at 25oC in pure water.

Slide 12

Figure 14.7 Two Water Molecules React to Form H3O+ and OH-

Figure 14.7 Two Water Molecules React to Form H3O+ and OH-

Slide 13

The pH Scale

The pH Scale

The pH scale provides a convenient way to represent solution acidity. The pH is a log scale based on 10.

pH  log[H+]

pH in water ranges from 0 to 14. The pH decreases as [H+] increases.

Kw = 1.00  1014 = [H+] [OH]

pKw = -log Kw = 14.00 = pH + pOH

As pH rises, pOH falls (sum = 14.00).

pOH = -log [OH-]

Slide 14

Figure 14.8 The pH Scale and pH Values of Some Common Substances

Figure 14.8 The pH Scale and pH Values of Some Common Substances

Slide 15

Calculating the pH of Strong Acid Solutions

Calculating the pH of Strong Acid Solutions

Calculate the pH of 1.0 M HCl.

Since HCl is a strong acid, the major species in solution are H+, Cl- and H2O

To calculate the pH we will focus on major species that can furnish H+. The acid is completely dissociates in water producing H+ and water also furnishes H+ by autoionization by the equilibrium

H2O(l) H+(aq) + OH-(aq)

In pure water at 25oC, [H+] is 10-7M and in acidic solution even less than that. So the amount of H+ contributed by water is negligible compared with the 1.0M H+ from the dissociation of HCl.

pH = -log [H+] = -log (1.0) = 0

Slide 16

Solving Weak Acid Equilibrium Problems

Solving Weak Acid Equilibrium Problems

List major species in solution.

Choose species that can produce H+ and write reactions.

Based on K values, decide on dominant equilibrium.

Write equilibrium expression for dominant equilibrium.

List initial concentrations in dominant equilibrium.

Go to page:
 1  2  3  4 

Contents

Last added presentations

2010-2019 powerpoint presentations