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Acids and Bases

Key Concepts:

Terms in this set (34)

Arrhenius Definition of Acids and Bases

Arrhenius Acid- Generates H+ in solution
Arrhenius Base- Generates OH- in solution

Bronsted-Lowry Definition of Acids and Bases

Acid- Generates H+ in solution (hydrogen donor)
Base- Accepts H+ in solution (hydrogen acceptor)

Lewis Definition of Acids and Bases

Acid- Acts an electron pair acceptor
Base- Acts an electron pair donor

H+ is never present alone in solution- Instead they combine with water to form hydronium (H3O+) ions

Definition of a Strong Acid

A strong acid completely dissociates in solution- becomes 100% ions
- Due to high ion concentrations, strong acids are good electrical conductors

Conductivity vs. pH

inversely proportional
- As pH decreases, conductivity increases

Equilibrium Expression of an Acid

Ka= [H3O+][conjugate base]/[acid]
**water is NEVER included in Ka expression

Equilibrium Expression of a Base

Kb= [OH-][conjugate acid]/[base]

Ka of a Strong Acid vs a Weak Acid

Strong acid Ka >>>1
Weak acid Ka <<<1

Strong acid
dissociates to H3O+ and Cl- in solution

Strong acid
dissociates to H3O+ and Br- in solution

Strong acid
dissociates to H3O+ and I- in solution

Strong acid
dissociates to H3O+ and NO3- in solution

Strong acid
dissociates to H3O+ and SO4- in solution

Strong acid
dissociates to H3O+ and ClO4- in solution

Identify the Acid and Base in the Forward Reaction:
HCl (g) + H2O (l) <--> H3O+ (aq) + Cl- (aq)

acid- HCl (g)
base- H2O (l)

Identify the Acid and Base in the Reverse Reaction:
HCl (g) + H2O (l) <--> H3O+ + Cl-

acid- H3O+ (aq)
base- Cl- (aq)

What is the Term for the Acid/Base Pairs on the Two Sides of the Equation:
HCl (g) + H2O (l) <--> H3O+ + Cl-

HCl/Cl- - HCl is the acid and Cl- is the conjugate base

H2O/H3O+ - H2O is the base and H3O+ is the conjugate acid

The molecule formed when an acid loses its proton (HA --> H3O+ + A-)
A- is the conjugate base

The molecule formed when a base accepts a proton (A- --> HA)
HA- is the conjugate acid

Equilibrium Constant of Water (Kw)

Ka of a Strong Acid

Ka of a Weak Acid

Relationship between Ka and Kb

The larger Ka (stronger acid) has a smaller Kb of its conjugate base (weaker base)
- inversely proportional

What does "p" stand for in pH questions?

-log of a concentration

Based on the Reaction-
HA (aq) + H2O (l) <--> A- (aq) + H3O+ (aq)
What Would be the Effect of Decreasing pH on the concentration of each molecule present?

[H3O+]- increases causing reaction to shift to the left
[HA]- increases
[A-]- decreases

Based on the Reaction-
HA (aq) + H2O (l) <--> A- (aq) + H3O+ (aq)
What Would be the Effect of Increasing pH on the concentration of each molecule present?

[H3O+]- decreases causing reaction to shift to the right
[HA]- decreases
[A-]- increases

Does the Overall Concentration Change as pH of a Solution Changes?

No- all molecules are present from beginning to end, but they shift between the acid and base form depending on the pH

Equivalence Point

[H3O+]=[A-]
pKa = pH at this point

protonated species is present

deprotonated species is present

Poly-protic Acids

Acids that have more than one H+ that could be donated in solution
- Each H+ has its own pKa

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