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+