Acid/ Base Definitions

Arrhenius Definitions Acid – H+/H3O+ producer Base – OH- producer Good for strong acids and bases

Bronsted-Lowry Definition Acid – proton (H+) donor Base – proton acceptor Accounts for some weak bases which do not have an OH-

Lewis Definition Acid – electron pair acceptor Base – electron pair donor Encompasses even more than the Bronsted-Lowry definition

Identify the Lewis acid and base Ni2+ + 6NH3  Ni(NH3)62+ H+ + H2O  H3O+

Conjugate Acid/Base In every acid/base reaction, there are actually two acids and two bases NH3 + HF → F- + NH4+ On the reactant side, HF is an acid so it has a Ka, but on the product side F- the is a base so it has a Kb

Relationship Between Ka and Kb Ka x Kb = Kw pK = - log K pKa + pKb = 14.00

Example Calculate the Kb for the F- ion if the Ka for its conjugate acid is given in Appendix A5.1. Calculate the Ka for the ammonium ion, NH4+.

Example Calculate the pH of a .30M NaF solution. The Ka for HF is 7.2x10-4.