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Acids and Bases

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
Hydronium Ions
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
HCl
Strong acid
dissociates to H3O+ and Cl- in solution
HBr
Strong acid
dissociates to H3O+ and Br- in solution
HI
Strong acid
dissociates to H3O+ and I- in solution
HNO3
Strong acid
dissociates to H3O+ and NO3- in solution
H2SO4
Strong acid
dissociates to H3O+ and SO4- in solution
HClO4
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
Conjugate Base
The molecule formed when an acid loses its proton (HA --> H3O+ + A-)
A- is the conjugate base
Conjugate Acid
The molecule formed when a base accepts a proton (A- --> HA)
HA- is the conjugate acid
Equilibrium Constant of Water (Kw)
Kw= 1.0x10^-14
Ka of a Strong Acid
Ka >> 1
Ka of a Weak Acid
Ka << 1
Relationship between Ka and Kb
The larger Ka (stronger acid) has a smaller Kb of its conjugate base (weaker base)
- inversely proportional
(Ka)(Kb)
= Kw
What does "p" stand for in pH questions?
-log of a concentration
pKa + pKb
= pKw = 14
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
pH < pKa
protonated species is present
pH > pKa
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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