Acids of Bases

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HOBr is a weaker acid
than HBrO3. Account
for this fact.
Strong Acid/Weak Acid

The number of oxygen atoms will effect the strength
of the acid. HOBr has a single oxygen atom while
HBrO3 contains three.


Charge of X



Oxygen is a very electro negative atom and will draw
electrons away from the H-Br bond thus weakening the bond
making it easier to dissociate when in dissolved in water. The
more oxygen atoms the weaker the H-Br bond.
The charge on the X which in this case is the Br atom has a
different charge in HOBr (+1) than in HBrO3 (+5)
Strength of O-H Bond
Strength of X-O Bond
Arrhenius Acid Base Concept
Arrhenius Acid/Base Concept




Acids produce Hydrogen ions (H+) within an aqueous
solution
Bases produce Hydroxide Ions (OH-) in solution
Definition is limited because it applies only to acids and bases
that can dissociate OH- and H+ ions
Examples:
-
NaOH will dissociate into Na+ and OHHCl will dissociate into H+ and Cl-
Bronsted-Lowry Model

The model definition of Acid/Base





Bronsted Acid – A proton “donor”
Bronsted Base – A proton “acceptor”
The definition applies to many more molecules that may
exhibit Acid/Base qualities but do not directly produce OHor H+ ions.
Every Acid and Base has a conjugate Acid or Base
Water can act as an acid and a base

H3O+ (Hydronium ion) (acid) and OH- (Base)
Bronsted-Lowry Model

Example of Bronsted Base

NH3(aq) + H2O(l)  NH4+(aq) + OH-(aq)
Base

Acid
Conjugate Acid
Conjugate Base
Example of Bronsted Acid

HC2H3O2(aq) + H2O(l)  H3O+(aq) + C2H3O2-(aq)
Weak Acid
Base
Conjugate Acid
Conjugate Base
Lewis Acid/Base Definition

Lewis Acid/Base Definition
Lewis Acid – Electron Pair Acceptor
 Lewis Base – Electron Pair Donor
 Encompasses an even wider variety of molecules
(Bronsted and Arrhenius) even ones that do not
donate protons or produce OH- ions.
 Must be aware of the Lewis structure of a particular
molecule to determine whether it is a Lewis Acid or
Base.

Lewis Acid/Base Definition

Examples

BF3(g) + NH3(g)  F3BNH3(g)
BF3 is the Lewis Acid because it has no free unpaired
electrons with only has 6 electrons around the central
atom (Boron will require one more pair of electrons to
complete the valence shell)
 NH3 is the Lewis Base because the molecule has a
completed octet valence shell with free unpaired electrons
on the central atom. The BF3 will accept these unpaired
electrons and form a covalent bond.

Lewis Acid/Base Definition

Example

Ni2+(aq) + 6NH3(aq)  [Ni(NH3)6]2+(aq)
Ni2+ is the Lewis Acid because it is a cation which will
attract negatively charged electrons to toward itself.
 The NH3 is the Lewis Base because it provides the free
unpaired electrons for the Ni2+

Lewis Acid/Base Definition

Example
Even earlier definitions are encompassed in the
Lewis Acid Model
 H+ + H2O  H3O+

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