Buffers help acid-base equilibrium systems to resist changes in pH.  There is extra help on Wednesday.  The test is on Thursday.
Homework:  Read p.615-620 and answer p.620 Practice #1, 2; Section #2-4

Indicators play an important role in titrations.  The choice of a good indicator depends on whether you use strong or weak acids or bases to react, and therefore, on whether the salt produced causes hydrolysis.  Text reference is p.595-613.
Your unit test for acid-base equilibrium is on Thursday, January 13, 2010.
Homework:  State the difference between "endpoint" and "equivalence".  Answer p.599 #1, 2; p.613 #10, 1, 2, 5; p.614 #10
Review for test: p.636 #2, 11, 13-15, 17-30, 32-39; p.641 #27-29, 32, 33, 38, 40, 42, 46, 48, 51

Some salt solutions are neutral, but some are acidic and some are basic.  Consult your text p.581-587 for the reason, and some examples.  Unit 4 Test, Part 2 is next Thursday. January 13.
Homework:  p.579 #16; p.588 #1, 2; p.594 #2, 4, 5

Read p.574 about Ka of polyprotic acids.  Kb is similar to Ka, but is for weak bases.  Consult p.570-573.  Some weak bases do not have their Kb values listed in the table in the back of the text.  To calculate these, see p.570.
Homework:  p.579 #9, 15; p.574 #13

Weak acids only partially ionize, setting up an equilibrium between the whole acid molecule and the ions it makes.  From this, we get an equilibrium constant for acids.  Consult the text, p.542-551, 563-570.
Homework:  p.568 #7, 8; p.570 #9

We reviewed the pH concept, learned about pOH and the autoionization constant of water, Kw.  The text reference is p.532-549.
Homework:  p.537 #5; p.540 #10; p.546 #13; p.549 #18