Lesson Plan

GLEs

GLE 32: Determine the concentration of an unknown acid or base by using

data from a titration with a standard solution and an indicator

(PS-H-D2).

GLE 33: Calculate pH of acids, bases, and salt solutions based on the

concentration of hydronium and hydroxide ions (PS-H-D2). GLE 35: Predict products (with phase notations) of simple reactions,

including acid/base, oxidation/reduction, and formation of

precipitates (PS-H-D3).

Lesson Plan

Essential Question(s) What does the pH of a solution mean?

Objective(s)

SWABT 1. How H+ and OH- are related in an aqueous solution. 2. Classify a solution as neutral, acidic, or basic using pH. 3. Identify two methods that are used to measure pH.

Vocabulary

u  Self-ionization u  Neutral solution u  ion-product constant for water (Kw) u  Acidic solution u  Basic solution u  pH

To Do Now

1. Arrhenius acid or base? a. HBr b. KOH c. CH3COOH d. KCl

2. Identify the monoprotic acids in the above examples.

3. F-(aq) + H2O è HF(aq) + OH-

Identify the acid, base, conjugate acid, conjugate base.

4. True or False.

An acid is a Hydrogen ion acceptor and a base is a Hydrogen ion donor.

19.2 H ions & Acidity

Unit 7: SOLUTIONS & ACIDS & BASES

19 ACIDS, BASES, AND SALTS

Acids Bases

Self-Ionization

A small amount of water ionizes to produce H3O+ and OH-.

1

2 water molecules out of every billion water molecules

Pure Water: Neutral

At 250C, in pure water, the concentration of H+ (or H3O+) and OH- is only 1 x 10-7 M. Since the concentrations of H+ and OH- are equal, water is a neutral solution.

2

Ion-Product Constant for Water (Kw)

For water, the product of the H+ and OH- concentrations is called Kw and Kw = 10-14. Kw = [H+] x [OH-] = 1 x 10-7 x 1 x 10-7 = 10-14

3

Acidic Solutions

When an acid is added to water, the acid releases H+, thus increasing the total concentration of H+ to greater than 1 x 10-7M. Solutions in which the H+ concentration is greater than OH- concentration are called Acidic solutions.

4

HCl + H2O H3O+(aq) + Cl-(aq)

Basic Solutions

When a base is added to water, the base releases OH- thus increasing the total concentration of OH- to greater than 1 x 10-7M. Solutions in which the OH- concentration is greater than H+ concentration are called Basic (or Alkaline) solutions.

5

NaOH + H2O Na+(aq) + OH-(aq)

pH Concept

The pH is defined as the negative logarithm of the H+ ion concentration. pH = -log10 [H+]

6

pH of Water

pH = -log10 [H+] pH = -log (1 x 10-7) = -(log 1 + log 10-7) = -(0.0 + (-7log10)) = -(-7 x 1) = 7

7

pH and Acidic, Basic & Neutral Solutions

A solution with a pH less than 7.0 is acidic. A solution with a pH greater than 7.0 is basic. A solution with a pH equal to 7.0 is neutral.

8

pH Scale

9

H+

(mol/L) 100 10-1 10-2 10-3 10-4 10-5 10-6 10-7 10-8 10-9 10-10 10-11 10-12 10-13 10-14

OH-

(mol/L) 10-14 10-13 10-12 10-11 10-10 10-9 10-8 10-7 10-6 10-5 10-4 10-3 10-2 10-1 100

A side B side

Acidic Basic

pH 0 1 2 3 4 5 6 7 8 9 10 11 12 13 14

pH of Common Substances

Measuring pH: 1. pH Indicators

Measuring pH: 1. pH Indicators

Measuring pH: 2. pH Meters

Guided Practice

Guided Practice

1. How are the concentrations of Hydrogen ions and Hydroxide ions related in an aqueous solution?

Guided Practice

2. What is the range of pH values in the following solutions?

basic

acidic

neutral

Guided Practice

3. What methods can you use to measure the pH of a solution?

Guided Practice

4. What happens to the [H+] as the pH of a solution decreases?

Guided Practice

5. In terms of H+ and OH-, how do basic solutions differ from acidic solutions?

Exit Ticket

1. A solution has a H+ concentration of 1 x 10-6. Is this solution acidic, basic, or neutral?

2. What is the OH- concentration of the above solution?

3. How can you increase the pH of a solution from 6.0 to

10.0?