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Chapter 9Acids and Bases

Acids and Bases

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Acids and Bases – What they do in water

Acids produce H+ in aqueous solutions water

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

Bases produce OH- in aqueous solutions

water

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

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Acids

Produce H+ (as H3O+) ions in water

Produce a negative ion (-) too

Taste sour

Corrode metals

React with bases to form salts and water

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Bases

Produce OH- ions in water

Taste bitter, chalky

Are electrolytes

Feel soapy, slippery

React with acids to form salts and water

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Learning Check AB1

Describe the solution in each of the following as: 1) acid 2) base or 3)neutral.

A. ___soda

B. ___soap

C. ___coffee

D. ___ wine

E. ___ water

F. ___ grapefruit

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Solution AB1

Describe each solution as:

1) acid 2) base or 3) neutral.

A. _1_ soda

B. _2_ soap

C. _1_ coffee

D. _1_ wine

E. _3_ water

F. _1_ grapefruit

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Learning Check AB2

Identify each as characteristic of an A) acid or B) base

____ 1. Sour taste

____ 2. Produces OH- in aqueous solutions

____ 3. Chalky taste

____ 4. Is an electrolyte

____ 5. Produces H+ in aqueous solutions

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Solution AB2

Identify each as a characteristic of an A) acid or B) base

_A_ 1. Sour taste

_B_ 2. Produces OH- in aqueous solutions

_B_ 3. Chalky taste

A, B 4. Is an electrolyte

_A_ 5. Produces H+ in aqueous solutions

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Some Common Acids

HCl hydrochloric acid

HNO3 nitric acid

H3PO4 phosphoric acid

H2SO4 sulfuric acid

CH3COOH acetic acid

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Learning Check AB3

Give the names of the following

A. HBr (aq) 1. bromic acid

2. bromous acid

3. hydrobromic acid

B. H2CO3 1. carbonic acid

2. hydrocarbonic acid

3. carbonous acid

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Solution AB3

A. HBr 3. hydrobromic acid

The name of a nonoxy acid begins with the prefix hydro- and ends with -ic acid. In a nonoxy acid, the negative anion end in -ide.

B. H2CO3 1. carbonic acid

The name of an oxyacid is named with the stem of the anion (carbonate) changed to

-ic acid

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Some Common Bases

NaOH sodium hydroxide

KOH potassium hydroxide

Ba(OH)2 ________________________

Mg(OH)2 ________________________

Al(OH)3 aluminum hydroxide

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Learning Check AB4

Match the formulas with the names:

A. ___ HNO2 1) hydrochloric acid

B. ___ Ca(OH)2 2) sulfuric acid

C. ___ H2SO4 3) sodium hydroxide

D. ___ HCl 4) nitrous acid

E. ___ NaOH 5) calcium hydroxide

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Solution AB4

Match the formulas with the names:

A. _4__ HNO2 1) hydrochloric acid

B. _5__ Ca(OH)2 2) sulfuric acid

C. _2__ H2SO4 3) sodium hydroxide

D. _1__ HCl 4) nitrous acid

E. _3__ NaOH 5) calcium hydroxide

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Learning Check AB5

Acid, Base Nameor Salt

CaCl2 ______ _________________

KOH ______ _________________

Ba(OH)2 ______ _________________

HBr ______ _________________

H2SO4 ______ __________________

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Solution AB5

Acid, Base Nameor Salt

CaCl2 salt calcium chloride

KOH base potassiuim hydroxide

Ba(OH)2 base barium hydroxide

HBr acid hydrobromic acid

H2SO4 acid sulfuric acid

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Acids & Bases –What they do with H+

Acids are hydrogen ion (H+) donors

Bases are hydrogen ion (H+) acceptors

HCl + H2O H3O+ + Cl-

donor acceptor + -

+ +

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Neutralization Reactions

When acid and bases with equal amounts of hydrogen ion H+ and hydroxide ions OH- are mixed, the resulting solution is neutral.

NaOH (aq) + HCl(aq) NaCl + H2O

base acid salt water

Ca(OH)2 + 2 HCl CaCl2 + 2H2Obase acid salt water

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Neutralization

H3O+ and OH- combine to produce water

H3O+ + OH- 2 H2O

from acid from base neutral

Net ionic equation:

H+ + OH- H2O

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Ionization of Water

Occasionally, in water, a H+ is transferred between H2O molecules

. . . . . . . .H:O: + :O:H H:O:H + + :O:H-

. . . . . . . . H H H

water molecules hydronium hydroxide ion (+) ion (-)

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Pure Water is Neutral

Pure water contains small, but equal amounts of ions: H3O+ and OH-

H2O + H2O H3O+ + OH-

hydronium hydroxide

ion ion

1 x 10-7 M 1 x 10-7 MH3O+ OH-

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Ion Product of Water Kw

[ ] = Molar concentration

Kw = [ H3O+ ] [ OH- ]

= [ 1 x 10-7 ][ 1 x 10-7 ]

= 1 x 10-14

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Acids

Increase H+

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

(aq)

More [H3O+] than water > 1 x 10-7M

As H3O+ increases, OH- decreases

[H3O+] > [OH-]H3O+

OH-

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Bases

Increase the hydroxide ions (OH-)

H2O

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

More [OH-] than water, [OH-] > 1 x 10-7M

When OH- increases, H3O+ decreases

[OH] > [H3O+]

H3O+OH-

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pH

Indicates the acidity [H3O+] of the solution

pH = - log [H3O+]

From the French pouvoir hydrogene

(“hydrogen power” or power of

hydrogen)

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Concentration changes by powers of 10

pH =1 has 10x more than pH = 2

pH = 1 has 100x more than pH = 3

More Less

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

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In the expression for [H3O+]

1 x 10-exponent

the exponent = pH

[H3O+] = 1 x 10-pH M

pH

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pH Range

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

Neutral

[H+]>[OH-] [H+] = [OH-] [OH-]>[H+]

Acidic Basic

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Some [H3O+] and pH

[H3O+] pH

1 x 10-5 M 5

1 x 10-9 M 9

1 x 10-11 M 11

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7 8 9 10 11 12 133 4 5 62 141 9 10 11 123 4 5 621

Neutral Weak Alkali

Strong

Alkali

Weak Acid

Strong Acid

The pH Scale

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Detecting Acids and Bases

• You can detect an acid using an indicator.

• INDICATOR - A substance that changes color in the presence of an acid or a base.

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INDICATORS• Litmus paper is an indicatorAn acid turns blue litmus paper redA base turns red litmus paper blue

• Cabbage juice can be used as an indicator

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• There are several ways to test pHThere are several ways to test pH

– Blue litmus paper (red = acid)Blue litmus paper (red = acid)

– Red litmus paper (blue = basic)Red litmus paper (blue = basic)

– pH paper (multi-colored)pH paper (multi-colored)

– pH meter (7 is neutral, <7 acid, >7 base)pH meter (7 is neutral, <7 acid, >7 base)

– Universal indicator (multi-colored)Universal indicator (multi-colored)

– Indicators like phenolphthaleinIndicators like phenolphthalein

– Natural indicators like red cabbage, Natural indicators like red cabbage, radishesradishes

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