Acids

Arrhenius acids • produce H+ ions in water.• are electrolytes.• have a sour taste. • turn litmus red.• neutralize bases.

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Note acid name endings: -ic (if anion was –ide or –ate)-ous (if anion was –ite)

Acids you need to know by name and formula (see Syllabus)

• Hydrochloric acid = HCl• Hydrofluoric acid = HF• Sulfuric acid = H2SO4

• Phosphoric acid = H3PO4

• Carbonic acid = H2CO3

• Nitric acid = HNO3

• Acetic acid = HC2H3O2 = CH3COOH• Hydrogen sulfide = H2S

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Dihydrogen phosphate ion = H2PO4-

Monohydrogen phosphate ion = HPO42-

Bicarbonate ion = HCO3-

Bases

Arrhenius bases • produce OH− ions

(hydroxide ions) in water.• taste bitter or chalky.• are electrolytes.• feel soapy and slippery.• neutralize acids.

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Hydroxides are typical Arrhenius Bases

BrØnsted-Lowry Acids and BasesAccording to the BrØnsted-Lowry theory,• acids donate a proton (H+). • bases accept a proton (H+).

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NH3, a BrØnsted-Lowry BaseIn the reaction of ammonia and water,

• NH3 is the base that accept H+.

• H2O is the acid that donates H+.

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NH3

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Comparing Acids and Bases

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Identify compound as acid or based by given property and formula.

Identify each as a characteristic of an

A) acid or B) base.

1. has a sour taste

2. produces OH- in aqueous solutions

3. has a chalky taste

4. is an electrolyte

5. produces H+ in aqueous solutions

Learning Check

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Strengths of Acids and Bases

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Strong and Weak Acids• In an HCl solution, the

strong acid HCl dissociates 100%.

• A solution of the weak acid CH3COOH contains mostly molecules and a few ions.

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• A strong acid completely ionizes (100%) in aqueous solutions. Is a strong electrolyte.HCl(g) + H2O(l) H3O+ (aq) + Cl− (aq)

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A weak acid dissociates only slightly in water to form a few ions in aqueous solutions.

H2CO3(aq) + H2O(l) H3O+(aq) + HCO3− (aq)

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Strong Bases

Strong bases

• are formed from metals of Groups 1A (1) and 2A (2).

• include LiOH, NaOH, KOH, and

Ca(OH)2.

• dissociate completely in water.

KOH(s) K+(aq) + OH−(aq)

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Weak Bases

Weak bases

• are most other bases.

• dissociate only slightly in water.

• form only a few ions in water.

NH3(g) + H2O(l) NH4+(aq) + OH−(aq)

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Ionization of Water

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H2O + H2O H3O+ + OH-

Pure Water is Neutral

In pure water, • the ionization of water molecules

produces small, but equal quantities of H3O+ and OH− ions.

• molar concentrations are indicated in brackets as [H3O+] and [OH−].

[H3O+] = 1.0 x 10−7 M

[OH−] = 1.0 x 10−7 M

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The ion product constant, Kw, for water

• is the product of the concentrations of the hydronium (H3O+ or H+ hydrogen ion) and hydroxide ions (OH-).

Kw = [ H3O+] [ OH− ]

• can be obtained from the concentrations in pure water.

Kw = [ H3O+] [ OH− ]

Kw = [1.0 x 10− 7 M] x [ 1.0 x 10− 7 M]

= 1.0 x 10− 14

Ion Product of Water, Kw

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Acidic Solutions

Adding an acid to pure water • increases the [H3O+].

• cause the [H3O+] to exceed 1.0 x 10-7 M.

• decreases the [OH−].

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Basic Solutions

Adding a base to pure water

• increases the [OH−].

• causes the [OH−] to exceed 1.0 x 10− 7M.

• decreases the [H3O+].

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acidic – neutral – basic solutions

[H3O+] determines acid or neutral or base

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1.0 x 10-7M = 0.0000001 = neutral

If < -7 (ie -1 through -6) = acidicIf > -7 (ie -8 through -14) = basic

Calculate [H3O+] or [OH-]

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Kw = 1.0×10-14 =[H3O+] x [OH- ] If [H3O

+ ] is known:

If [OH- ] is known:

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Calculating [H3O+]

What is the [H3O+] of a solution if [OH−] is 5.0 x 10-8 M?

STEP 1: Write the Kw for water.

Kw = [H3O+ ][OH− ] = 1.0 x 10−14

STEP 2: Rearrange the Kw expression.

STEP 3: Substitute [OH−].

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][OH

100.1]OH[

-

14

3

8-

14

3 105.0

100.1]OH[ 2.0 × 10-7 M

If lemon juice has [H3O+] of 2 x 10−3 M, what is the [OH−] of the solution?

Rearrange the Kw to solve for [OH- ]

Kw = [H3O+ ][OH− ] = 1.0 x 10−14

Learning Check

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3

14

3

w

102

100.1

]O[H

K]OH[ 5 x 10−12 M

The [OH−] of an ammonia solution is 4.0 x 10−2 M. What is the [H3O+ ] of the solution?

Learning Check

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][OH

100.1]OH[

-

14

3

2-

14

3 104.0

100.1]OH[ 2.5 x 10−13 M