Chemistry 19.1

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Chemistry 19.1

© Copyright Pearson Prentice Hall

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Acid-Base Theories

Bracken Cave, near San Antonio, Texas, is home to twenty to forty million bats. Visitors to the cave must protect themselves from the dangerous levels of ammonia in the cave. Ammonia is a byproduct of the bats’ urine. You will learn why ammonia is considered a base.

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Acid-Base Theories >

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Acid-Base Theories >Acid-Base Theories > Properties of Acids and Bases

Properties of Acids and Bases

What are the properties of acids and bases?

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Acid-Base Theories >Acid-Base Theories >Acid-Base Theories > Properties of Acids and Bases

Acids

Acids taste sour, will change the color of an acid-base indicator, and can be strong or weak electrolytes in aqueous solution.

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Acid-Base Theories >Acid-Base Theories >Acid-Base Theories >Acid-Base Theories >Acid-Base Theories >Acid-Base Theories > Properties of Acids and Bases

Citrus fruits contain citric acid. Tea contains tannic acid.

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Acid-Base Theories >Acid-Base Theories >Acid-Base Theories > Properties of Acids and Bases

Bases

Bases taste bitter, feel slippery, will change the color of an acid-base indicator, and can be strong or weak electrolytes in aqueous solution.

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Acid-Base Theories >Acid-Base Theories >Acid-Base Theories >Acid-Base Theories >Acid-Base Theories >Acid-Base Theories > Properties of Acids and Bases

Antacids use bases to neutralize excess stomach acid. The base calcium hydroxide is a component of mortar.

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Acid-Base Theories >Acid-Base Theories >Acid-Base Theories > Arrhenius Acids and Bases

Arrhenius Acids and Bases

How did Arrhenius define an acid and a base?

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Acid-Base Theories >Acid-Base Theories >Acid-Base Theories > Arrhenius Acids and Bases

Arrhenius said that acids are hydrogen-containing compounds that ionize to yield hydrogen ions (H+) in aqueous solution. He also said that bases are compounds that ionize to yield hydroxide ions (OH–) in aqueous solution.

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Acid-Base Theories >Acid-Base Theories >Acid-Base Theories >Acid-Base Theories >Acid-Base Theories >Acid-Base Theories >19.1 Arrhenius Acids and Bases

Hydrochloric Acid

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Acid-Base Theories >Acid-Base Theories >Acid-Base Theories >Acid-Base Theories >Acid-Base Theories >Acid-Base Theories > Arrhenius Acids and Bases

Arrhenius Acids

• Acids that contain one ionizable hydrogen, such as nitric acid (HNO3), are called monoprotic acids.

• Acids that contain two ionizable hydrogens, such as sulfuric acid (H2SO4), are called diprotic acids.

• Acids that contain three ionizable hydrogens, such as phosphoric acid (H3PO4) are called triprotic acids.

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Acid-Base Theories >Acid-Base Theories >Acid-Base Theories >Acid-Base Theories >Acid-Base Theories >Acid-Base Theories > Arrhenius Acids and Bases19.1

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Arrhenius Bases

Hydroxide ions are one of the products of the dissolution of an alkali metal in water.

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Acid-Base Theories >Acid-Base Theories >Acid-Base Theories >Acid-Base Theories >Acid-Base Theories >Acid-Base Theories > Arrhenius Acids and Bases19.1

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Milk of magnesia is a base used as an antacid.

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Acid-Base Theories >Acid-Base Theories > Brønsted-Lowry Acids and Bases

Brønsted-Lowry Acids and Bases

What distinguishes an acid from a base in the Brønsted-Lowry theory?

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Acid-Base Theories >Acid-Base Theories >Acid-Base Theories > Brønsted-Lowry Acids and Bases

The Brønsted-Lowry theory defines an acid as a hydrogen-ion donor, and a base as a hydrogen-ion acceptor.

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Acid-Base Theories >Acid-Base Theories >Acid-Base Theories >Acid-Base Theories >Acid-Base Theories >Acid-Base Theories > Brønsted-Lowry Acids and Bases

Why Ammonia is a Base

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Conjugate Acids and Bases

• A conjugate acid is the particle formed when a base gains a hydrogen ion.

• A conjugate base is the particle that remains when an acid has donated a hydrogen ion.

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• A conjugate acid-base pair consists of two substances related by the loss or gain of a single hydrogen ion.

• A substance that can act as both an acid and a base is said to be amphoteric.

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Acid-Base Theories >Acid-Base Theories >Acid-Base Theories >Acid-Base Theories >Acid-Base Theories >Acid-Base Theories > Brønsted-Lowry Acids and Bases19.1

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A water molecule that gains a hydrogen ion becomes a positively charged hydronium ion (H3O+).

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Acid-Base Theories >Acid-Base Theories > Lewis Acids and Bases

Lewis Acids and Bases

How did Lewis define an acid and a base?

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Acid-Base Theories >Acid-Base Theories >Acid-Base Theories > Lewis Acids and Bases

Lewis proposed that an acid accepts a pair of electrons during a reaction, while a base donates a pair of electrons.

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Acid-Base Theories >Acid-Base Theories >Acid-Base Theories >Acid-Base Theories >Acid-Base Theories >Acid-Base Theories > Lewis Acids and Bases

• A Lewis acid is a substance that can accept a pair of electrons to form a covalent bond.

• A Lewis base is a substance that can donate a pair of electrons to form a covalent bond.

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Acid-Base Theories > Lewis Acids and Bases

Animation 25

Compare the three important definitions of acids and bases.

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Acid-Base Theories >Acid-Base Theories >Acid-Base Theories >Acid-Base Theories >Acid-Base Theories >Acid-Base Theories > Lewis Acids and Bases19.1


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Practice Problems for Conceptual Problem 19.1

Problem Solving 19.1

Solve Problem 1 with the help of an interactive guided tutorial.


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Section Quiz

-or-Continue to: Launch:

Assess students’ understanding of the concepts in Section

19.1 Section Quiz.

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1. Which of the following is NOT a characteristic of acids?

a. taste sour

b. are electrolytes

c. feel slippery

d. affect the color of indicators

19.1 Section Quiz.


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2. Which compound is most likely to act as an Arrhenius acid?

a. H2O

b. NH3.

c. NaOH.

d. H2SO4.

19.1 Section Quiz.


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19.1 Section Quiz.

3. A Lewis acid is any substance that can accept

a. a hydronium ion.

b. a proton.

c. hydrogen.

d. a pair of electrons.

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Chemistry 19.1

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