Acids
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Transcript of Acids
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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)
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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-
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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
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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.
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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-
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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
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[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
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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
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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
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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