Chapter 16 Acids & Bases

Acids vs. Bases Section 16.1 Arrhenius model Brønsted-Lowry model Ex: Oldest model; only applies to compounds that contain H+ or OH- ions Brønsted-Lowry model Refers to a compound’s ability to donate or accept an H+ ion Ex: HCl NH3 H2O

Brønsted-Lowry Acids and Bases Section 16.2 Water as Brønsted-Lowry acid/base: No such thing as H+ ion in solution (too unstable) Only H3O+ Proton transfer reactions:

Brønsted-Lowry Example NH3(aq) + H2O(l) NH4+(aq) + OH-(aq) Which acts as Brønsted-Lowry base? acid? H2O behaves as an amphoteric compound Capable of accepting OR donating H+ ions

Conjugate Acids/Bases The reactants and products associated with a proton transfer reaction are known as a conjugate acid-base pair:

Relative Strength of Acids and Bases The strength of an acid depends primarily on the willingness to donate or accept electrons i.e. strength of conjugate acid/base Equilibrium for strong acids lies heavily on the side of the deprotonated form and vice versa

The Autoionization of Water Section 16.3 Water has a very interesting property due to its amphoterism Capable of autoionization:

Calculating the [H3O+] An acid is added to water so that the hydrogen ion concentration is 0.25 M. Calculate the hydroxide ion concentration. See Sample Exercise 16.4 (Pg. 674)

The pH Scale Section 16.4 Concentrations of either H3O+ or OH- are typically very small and therefore cumbersome The pH scale is a logarithmic scale and is much more convenient: pH = -log[H3O+] pOH = -log[OH-] pH + pOH = 14

pH of Common Substances

Strong Acids and Bases Section 16.5 For a compound to be classified as a strong acid or base it must completely dissociate into ions when placed into aqueous solution Very weak conjugate bases No equilibrium Ex: HCl(g) + H2O(l)  H3O+(aq) + NO3-(aq) There are 7 strong acids which you will have to remember: HCl, HBr, HI, HNO3, HClO3, HClO4, H2SO4