1. Chapter 16
Acids and Bases

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Acids and Bases
Characteristics of acids: sour, corrosive, conducts electricity
Characteristics of bases: bitter, slippery, corrosive, conducts electricity
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3. pure water, sugar solution
Electrolytes
Strong - conduct current efficiently
NaCl, HNO3
Weak - conduct only a small current
vinegar, tap water
Non - no current flows
pure water, sugar solution

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Acids
Strong acids -dissociate completely to produce H+ in solution
hydrochloric and sulfuric acid
Weak acids - dissociate to a slight extent to give H+ in solution
acetic and hydrofluoric
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5. HCl(aq) is completely ionized.

6. Acetic acid (HC2H3O2) exists in water mostly as undissociated molecules. Only a small percentage of the molecules are ionized.

7. Models of Acids and Bases
Arrhenius Concept:
Acids produce H+ in water
Bases produce OH in water
HCl  Cl + H+
NaOH  Na+ + OH-
NH3 + H2O  NH OH-
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Brønsted-Lowry:
Acids are H+ donors
Bases are H+ acceptors
examples: HCl + H2O  Cl + H3O+
acid base
NaOH + HCl  NaCl + H2O
NH3 + HCl  NH Cl-
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9. Conjugate Acid/Base Pairs
HA(aq) + H2O(l)  H3O+(aq) + A(aq)
conj conj conj conj
acid base acid base 1
conjugate base: like the conjugate acid, but with one less H
conjugate acid: like the conjugate base, but with one more H
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Question
Identify the conjugate acid base pairs:
HF + OH-  F- + H2O
NH3 + H2SO4  NH HSO4-
HClO4 + H2O  H3O+ + ClO4-
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11. Conjugate Acid/Base Strength
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12. Water as an Acid and a Base
Water is amphoteric (it can behave either as an acid or a base).
H2O  H+ + OH
Kw = 1  1014 = [H+][OH-]
If [H+] > [OH-] acidic
If [H+] < [OH-] basic
If [H+] = [OH-] neutral
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13. Reaction of Acid with Water
HCl + H2O  H3O+ + Cl-
H3O+ is called the hydronium ion
H3O+ is equivalent to H+
So we usually just write it like:
HCl  H Cl-
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Question:
Calculate the [H+] if [OH-] = 1.0 x 10-5 M
Is the solution acidic or basic?
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Question:
Calculate the [OH-] if the [H+] = 2.6 x 10-8 M
Is the solution acidic or basic?
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Question:
Calculate the [H+] and [OH-] for a 0.15 M HCl solution.
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Question:
Calculate the [H+] and [OH-] for a M H2SO4 solution.
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The pH Scale
pH = log[H+]
pH in water ranges from 0 to 14.
Kw = 1.00  1014 = [H+] [OH]
pKw = = pH + pOH
pOH = -log[OH-]
As pH rises, pOH falls (sum = 14.00).
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Question
Calculate the pH for the following:
[H+] = 1 x 10-9 M
[H+] = 3.2 x 10-3 M
[OH-] = 4 x 10-8 M
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The pH scale.
Acidic: pH < 7
Basic: pH > 7
Neutral: pH = 7
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Question
Calculate the pH for the following:
0.004 M HCl
1.5 M NaOH
0.015 M H2SO4
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Question
Calculate the [H+] for the following:
pH = 4.5
pH = 11.5
pOH = 5.6
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Indicators – turn a certain color at a particular pH
Litmus paper:
Is red in acidic solution
Is blue in basic solution
pH paper: has a combination of indicators to give a more precise measurement of pH
pH meter: uses voltage to measure the pH very accurately
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24. Figure 16.4: Useful pH ranges for several common indicators.
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Titration
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Titration
Standard solution: the solution of accurately known concentration
The buret holds the standard solution; the solution of unknown concentration is in the beaker
An indicator is in the beaker solution which will change color when the correct amount of standard solution is added (equivalence point)
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Titration
Equivalence point: equivalent amounts of acid and base have reacted
For a strong acid + strong base, the equivalence point occurs at pH = 7
The pH of the solution changes dramatically near the equivalence point
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The pH curve for the titration of mL of ? M HNO3 with M NaOH.
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Question
For the titration in the previous slide, calculate the concentration of the HNO3.
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Question
A 100 mL sample of 0.15 M HCl is titrated with 0.60 M KOH. What volume of KOH would be required to reach the endpoint?
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