1. Aqueous acetic acid (Ka = 1.8*10 -5 ) (Virtually no H 3 O + ions) ) Making a Buffer Solution: I Make a solution of a weak acid e.g., HCH 3 CO 2, or acetic acid (HAc for short) Strong Base (OH-) - - - - - - - - - Final Solution Effect of Strong Base Is Neutralized - - - - - - - -- - + => - + HAc Ac - H2OH2O OH - This solution counteracts the effect of a strong base by donating protons to the basic compound, forming water and preventing pH change + = Use this file in Presentation Mode

2. Aqueous CH 3 CO 2 - (Na ion not shown) Making a Buffer Solution: II Make a solution of Sodium Acetate (NaCH 3 CO 2 ) The conjugate base of Acetic Acid is formed (CH 3 CO 2 -, the “acetate ion”; Ac for short) The metal ion Na+ is a “spectator ion” and irrelevant to this chemistry Strong Acid (HCl) - - - - - - - - - + => + - - Ac - HAcCl - HCl This solution counteracts the effect of a strong base by donating protons to the basic compound, forming water and preventing pH change The chlorine ion is irrelevant to this chemistry + = Final Solution (Cl ions irrelevant)

3. Making a Buffer Solution: III A buffer is just a combination of the two solutions (weak acid plus its conjugate base) It combines the properties of these two solutions Neutralizes both strong acids and bases - - - - - - - - - Aqueous HAc (Ka = 1.8*10 -5 ) (Virtually no H 3 O+ ions) ) Conjugate Base (Ac - ) (Na irrelevant, not shown) - - - - - - - - - Buffer Solution Weak Acid, Conjugate Base Coexist in Solution Combine