Tuesday, March 10, 2009
Tues-Day 2
AP Chem- we drew out and explained how to make a buffer solution (4 different methods) and saw how a given buffer can "absorb"/react with a given quantity of added strong acid or strong base so that the pH does not change as significantly as it would if the same strong acid or strong base were added to water.
Buffers work by having (within a 10:1 or 1:10 molar ratio) available weak acid molecules and their conjugate bases so that one or the other will react with/neutralize added acid or base (same deal for basic buffers that have a weak base and its conjugate acid ions available).
We then quantitatively showed the pH difference between a solution of ethanoic acid and a buffer solution of ethanoic acid mixed with an equimolar quantity of sodium ethanoate.
We noted that the ICE tables in buffer problems have BOTH acid AND conjugate base quantities in the "I" initial concentration line. We let the concentration of H+ initially be ZERO as a convenience because we know that ONLY the "E" equilibrium line amounts are involved in our calculations with Ka.
We then saw a convenient little equation that is used for buffers: the Henderson-Hasselbalch equation.
Bio 6- finished discussing the structure and function of the female reproductive system and then began our discussion of the fascinating, multiple hormonal feedback regulated menstrual cycle.
The video is posted on Blackboard.
Bio 7/8- we discussed the structure and function of the female reproductive system and then began our discussion of the fascinating, multiple hormonal feedback regulated menstrual cycle.
The video is posted on Blackboard.
We did some microscopy in lab but were unsuccessful (good thing?) in finding dust mites on the slides.
Buffers work by having (within a 10:1 or 1:10 molar ratio) available weak acid molecules and their conjugate bases so that one or the other will react with/neutralize added acid or base (same deal for basic buffers that have a weak base and its conjugate acid ions available).
We then quantitatively showed the pH difference between a solution of ethanoic acid and a buffer solution of ethanoic acid mixed with an equimolar quantity of sodium ethanoate.
We noted that the ICE tables in buffer problems have BOTH acid AND conjugate base quantities in the "I" initial concentration line. We let the concentration of H+ initially be ZERO as a convenience because we know that ONLY the "E" equilibrium line amounts are involved in our calculations with Ka.
We then saw a convenient little equation that is used for buffers: the Henderson-Hasselbalch equation.
Bio 6- finished discussing the structure and function of the female reproductive system and then began our discussion of the fascinating, multiple hormonal feedback regulated menstrual cycle.
The video is posted on Blackboard.
Bio 7/8- we discussed the structure and function of the female reproductive system and then began our discussion of the fascinating, multiple hormonal feedback regulated menstrual cycle.
The video is posted on Blackboard.
We did some microscopy in lab but were unsuccessful (good thing?) in finding dust mites on the slides.
# posted by C @ 1:41 PM 
