I. Introduction to Acids & Bases
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Transcript of I. Introduction to Acids & Bases
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I. Introduction toAcids & Bases
I. Introduction toAcids & Bases
Ch. 19 – Acids & BasesCh. 19 – Acids & Bases
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A. PropertiesA. Properties
electrolytes electrolytes
turn litmus red
sour taste
react with metals to form H2 gas
slippery feel
turn litmus blue
bitter taste
vinegar, milk, soda, apples, citrus fruits
ammonia, lye, antacid, baking soda
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B. DefinitionsB. Definitions
ArrheniusArrhenius
HCl + H2O H3O+ + Cl–
•Acids Acids contain hydrogencontain hydrogen
•AcidsAcids form hydronium ions (H3O+) in aqueous solution
H
HH H H
H
ClClO O
–+
acid
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B. DefinitionsB. Definitions
ArrheniusArrhenius•Bases Bases contain a hydroxide groupcontain a hydroxide group•BasesBases form hydroxide ions (OH-) in
aqueous solution
NaOH Na+ + OH-
base
H2O
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B. DefinitionsB. Definitions
Brønsted-LowryBrønsted-Lowry
HCl + H2O Cl– + H3O+
•AcidsAcids are proton (H+) donors
•BasesBases are proton (H+) acceptors
conjugate acidconjugate base
baseacid
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B. DefinitionsB. Definitions
Brønsted-LowryBrønsted-Lowry
HBr + NaOH NaBr + H2O
•Conjugate AcidsConjugate Acids are the result after a base accepts a hydrogen ion
•Conjugate BasesConjugate Bases are the result after an acid donates a hydrogen ion
conjugate acidconjugate base
baseacid
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B. DefinitionsB. Definitions
H2O + HNO3 H3O+ + NO3–
CBCAAB
H2O + NH3 NH4+ + OH-
CA CBBA
Amphoteric – can be an acid or a base – can be an acid or a base
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B. DefinitionsB. Definitions
F -
H2PO4-
H2O
HF
H3PO4
H3O+
Give the conjugate base for each of the following:
Polyprotic – an acid with more than one H – an acid with more than one H++
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B. DefinitionsB. Definitions
Br -
HSO4-
CO32-
HBr
H2SO4
HCO3-
Give the conjugate acid for each of the following:
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C. StrengthC. Strength
Strong Acid/BaseStrong Acid/Base• 100% ionized in water• strong electrolyte
- +
HCl
HNO3
H2SO4
HBr
HI
HClO4
NaOH
KOH
KOH
RbOH
CsOH
Ca(OH)2
Ba(OH)2
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C. StrengthC. Strength
Weak Acid/BaseWeak Acid/Base• does not ionize completely• weak electrolyte
- +
HF
CH3COOH
H3PO4
H2CO3
HCN
NH3
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Ch. 19 – Acids & BasesCh. 19 – Acids & Bases
II. pH
(p. 644 – 658)
II. pH
(p. 644 – 658)
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pH water equilibriumpH water equilibrium
Pure water ionizes to a small extent to produce hydrogen ions and hydroxide ions
According to LeChatlier’s principle if an acid is dissolved in water the equilibrium will shift to the left decreasing the hydroxide ion concentration.
If a base is dissolved in water this decreases the hydrogen ion concentration.
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A. Ionization of WaterA. Ionization of Water
H2O (l)+ H2O (l) H3O+(aq)+ OH-
(aq)
Self-Ionization of Water
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Ion Product Constant for Water
• For all aqueous solutions, the product of the hydrogen-ion concentration and the hydroxide-ion concentration equals 1.0 x 10-14
• The ion production of water, Kw = [H3O+][OH–]
• Pure water contains equal concentrations of H+ and OH– ions, so [H3O+] = [OH–]
A. Ionization of WaterA. Ionization of Water
Kw = [H3O+][OH-] = 1.0 10-14
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A. Ionization of WaterA. Ionization of Water
Find the hydroxide ion concentration of 3.0 10-2 M HCl.
[H3O+][OH-] = 1.0 10-14
[3.0 10-2][OH-] = 1.0 10-14
[OH-] = 3.3 10-13 M
HCl → H+ + Cl-
3.0 10-2M 3.0 10-2M
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A. Ionization of WaterA. Ionization of Water
Find the hydronium ion concentration of 1.4 10-3 M Ca(OH)2.
[H3O+][OH-] = 1.0 10-14
[H3O+][2.8 10-3] = 1.0 10-14
[H3O+] = 3.6 10-12 M
Ca(OH)2 → Ca2+ + 2 OH-
1.4 10-3M 2.8 10-
3M
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pH = -log[H3O+]
B. pH ScaleB. pH Scale
0
7INCREASING
ACIDITY NEUTRALINCREASING
BASICITY
14
pouvoir hydrogène (Fr.)“hydrogen power”
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B. pH ScaleB. pH Scale
pH of Common SubstancespH of Common SubstancespH of Common SubstancespH of Common Substances
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B. pH ScaleB. pH Scale
pH = -log[H3O+]
pOH = -log[OH-]
pH + pOH = 14
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B. pH ScaleB. pH Scale
What is the pH of 0.050 M HNO3?
pH = -log[H3O+]
pH = -log[0.050]
pH = 1.30
Acidic or basic?Acidic
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B. pH ScaleB. pH Scale
What is the pH of 0.050 M Ba(OH)2?
[OH-] = 0.100 M
pOH = -log[OH-]
pOH = -log[0.100]
pOH = 1.00
pH = 13.00
Acidic or basic? Basic
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B. pH ScaleB. pH Scale
What is the molarity of HBr in a solution that has a pOH of 9.60?
pH + pOH = 14
pH + 9.60 = 14
pH = 4.40
Acidic
pH = -log[H3O+]
4.40 = -log[H3O+]
-4.40 = log[H3O+]
[H3O+] = 4.0 10-5 M HBr