CHEM 4400 Fall 

  Acid-Base Equilibria: a drink from the fountain of knowledge. 

  Acid base review, to equilibrate or not to equilibrate.

Ka for KOH is very large . Ka for acetic acid is 1.8 x 10-5

  1. What is the pH of 500 mL of a 0.015 M solution of KOH?

  2. What is the pH of a solution made by adding 25 ml of 2.0M HCl  to 475 mL of water.

  3. What is the pH of a 0.02 M solution of acetic acid?

  Hydroxide drops keep falling in my flask....

4.  Draw the titration curve for the titration of a 0.05 M solution of acetic acid with 0.1 M sodium hydroxide.

5.  Draw the titration curve for the titration of 0.1M glycine with 0.1M sodium hydroxide.  Glycine has a pKa of 2.35 for the carboxylic acid group and a pKa of 9.78 for the amino group.  The complete structure is in your book.


Buffy and the Vampire slayers:

6.  You need to make a buffer for your biochemistry laboratory experiment that involves intestinal mucosa cells.  These cells require a pH of 6.7 to survive.  Give the complete directions  (including substances, volumes and weights) for preparing 500 mL of this 0.2M buffer solution.  The following Ka values may be useful:

6.  Phosphoric acid is a weak acid and can be used to prepare buffer solutions.  If 1L of 0.01M phosphoric acid  has a starting pH of 7.4, and then an amount of 0.1M HCl is added to this buffer to change the pH to 5.6, what volume of 0.1M HCl has been added?

Anxious about all this chemistry review?  This one will calm your nerves:

7.  Acetylcholine is a potent neurotransmitter.  Concentrations in the synapses between nerves is regulated by the enzyme acetylcholinesterase.  This enzyme degrades acetylcholine to choline and acetic acid.  The acetic acid then dissociates to acetate ion and hydrogen ion.  How do we know that it completely dissociates? (Hint: the pH of the synapse is between 6.6 and 7.5)   Calculate the amount of acetylcholine present in 15 ml if the  addition of acetylcholinesterase decreases the pH from 7.4 to 6.8.  (The Ka for acetic acid is 1.74 x 10-5.)