1. ATB Question of the Day Day 1 4-19 0.108
The pH for a 0.10 M solution of a monoprotic acid is 1.2, what is the Ka?
0.108
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2. Assignment Day 1 4-19 page 669 #s 27-34  due Tuesday Day 5 4-17
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3. III. Strong and Weak Acids and Bases
Base Dissociation Constant – Kb
Write the Keq for the dissociation of NH3(aq) above.
*** for dilute aqueous solutions the concentration of water is a constant so,
[NH4+] * [OH-]
Keq =
[NH3] * [H2O]
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4. III. Strong and Weak Acids and Bases
Base Dissociation Constant – Kb
Or in general form:
 the base dissociation constant (Kb) measures the extent to which a base dissociates in aqueous solution, and so can be used to represent the strength of a base. The stronger the base, the higher the Kb value.
[conjugate acid] * [OH-]
Kb =
[base]
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5. III. Strong and Weak Acids and Bases
Differentiating Concentration and Strength:
Strength refers to the extent of ionization or dissociation of an acid or base, while concentration indicates how much of a substance is dissolved.  Recall that substances can dissolve without dissociating (sugar).
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6. III. Strong and Weak Acids and Bases
Differentiating Concentration and Strength:
*** Strength is independent of concentration and vice versa.
Acidic Solution
Molar Concentration
Relative Concentration
Relative Strength
Hydrochloric acid
12 M HCl
Concentrated
Strong
Gastric Juice (stomach acid)
0.08 M HCl
Dilute
Acetic acid
17 M CH3COOH
Weak
Vinegar
0.2 M CH3COOH
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7. IV. Neutralization Reactions
Acid-Base Reactions = Neutralization Reactions
 In general acids and bases react to produce a salt (ionic substance) and water.
 The complete reaction of a strong acid and a strong base produces a neutral solution – neutralization reaction.
Example: HCl(aq) + NaOH(aq)  NaCl(aq) + H2O(l)
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8. IV. Neutralization Reactions
Acid-Base Reactions = Neutralization Reactions
 Mole Ratios and Neutralization Reactions (example problem)
How many moles of sulfuric acid are needed to neutralize 0.50 moles of sodium hydroxide?
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9. Conjugate Acids and Bases
Brønsted-Lowry Acids and Bases
Conjugate Acids and Bases
The figure below shows the reaction that takes place when sulfuric acid dissolves in water.
The products are hydronium ions and hydrogen sulfate ions.
Use the figure to identify the two conjugate acid-base pairs.
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10. Acid-Base Definitions
Interpret Data
This table compares the definitions of acids and bases.
Acid-Base Definitions
Type
Acid
Base
Arrhenius
H+ producer
OH– producer
Brønsted-Lowry
H+ donor
H+ acceptor
Lewis
electron-pair acceptor
electron-pair donor
The Lewis definition is the broadest.
It extends to compounds that the Brønsted-Lowry theory does not classify as acids and bases.
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11. Identifying Lewis Acids and Bases
Sample Problem 19.1
Identifying Lewis Acids and Bases
Identify the Lewis acid and the Lewis base in this reaction between ammonia and boron trifluoride.
NH3 + BF3 → NH3BF3
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12. Are hydrogen-ion donors also electron-pair acceptors?
Yes. All substances defined as acids by the Brønsted-Lowry definition (an acid is a hydrogen-ion donor) are also defined as acids by the Lewis definition (an acid is an electron-pair acceptor). That means that these substances are both hydrogen-ion donors and electron-pair acceptors.
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13. Key Concepts
According to Arrhenius, acids are hydrogen-containing compounds that ionize to yield hydrogen ions in aqueous solution. Bases are compounds that ionize to yield hydroxide ions in aqueous solution.
According to Brønsted-Lowry theory, an acid is a hydrogen-ion donor and a base is a hydrogen-ion acceptor.
According to Lewis, an acid accepts a pair of electrons and a base donates a pair of electrons.
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14. Glossary Terms
hydronium ion (H3O+): the positive ion formed when a water molecule gains a hydrogen ion
conjugate acid: the particle formed when a base gains a hydrogen ion; NH4+ is the conjugate acid of the base NH3
conjugate base: the particle that remains when an acid has donated a hydrogen ion; OH– is the conjugate base of the acid water
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15. amphoteric: a substance that can act as both an acid and a base
Glossary Terms
conjugate acid-base pair: two substances that are related by the loss or gain of a single hydrogen ion; ammonia (NH3) and the ammonium ion (NH4+) are a conjugate acid- base pair
amphoteric: a substance that can act as both an acid and a base
Lewis acid: any substance that can accept a pair of electrons to form a covalent bond
Lewis base: any substance that can donate a pair of electrons to form a covalent bond
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16. BIG IDEA
Reactions
Chemists define acids and bases according to the ions they yield in aqueous solution.
Chemists also define acids and bases based on whether they accept or donate hydrogen ions, and whether they are electron-pair donors or acceptors.
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17. [conjugate acid] * [OH-] Kb = [base]
[NH4+] * [OH-]
Kb = Keq * [H2O] =
[NH3]
[H3O+] * [CH3COO-]
Ka = Keq * [H2O] =
[CH3COOH]
[conjugate acid] * [OH-]
Kb =
[base]
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18. [NH4+] * [OH-] Keq = [NH3] * [H2O]
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