Transcript Buffers: A Microscopic View CHM 102 Sinex Type your name in the textbox below: To advance slide: click outside of the textbox!

Buffers:
A Microscopic View
CHM 102 Sinex
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Here is the equilibrium that controls the buffer’s pH.
What are the two major components of the buffer?
answer
+
HA
the weak acid
(protonated form)
Give an example:
H+
Athe salt or acid anion,
which acts as a
weak base
(deprotonated form)
Playing the Le Chatelier Game with a Equilibrium Reaction
HA
A-
add acid
add base
H+
Count and enter:
OH-
HA
A-
A-/HA =
+
HA
H+
A-
(H )(A )
Ka =
(HA)
Ka
Ka (HA)
+
(H ) =
=
(A )
(A )
(HA)
+
-
salt/acid ratio
So change the salt/acid ratio and the (H+) responds!!!
+
HA
H+
A-
Predict the products
Add a small amount of acid to buffer:
answers
+
A-
H+
HA
Add a small amount of base to buffer:
+
HA
+
OH-
A-
H2O
How does the salt/acid ratio change for each addition above?
How does the salt/acid ratio change?
For a small amount of acid to buffer:
For a small amount of base to buffer:
Is there a limit to how much acid or base can be
added to a buffer and still have it buffer?
HINT: Why do we say a small amount of acid or
base? Look at the reactions…
To the reactions…
Why doesn’t a solution of HCl and NaCl buffer?
How does the chloride
ion function as a base?
Hint!!!
A-/HA =
What happens to
the buffer pH if it
is diluted?
What is the salt-to-acid ratio?
A-/HA =
Which box will be the best buffer?
HA
Box A
Explain your choice
A-
Box B
H+
Box C
Which box will not the buffer?
HA
Box A
Explain your choice
A-
Box B
H+
Box C
Which box has the highest pH?
HA
Box A
Explain your choice
A-
Box B
H+
Box C
If you are done…
Go to File and select Print
or
Hit the print button icon on the menu bar.
This will print out in handout format with 3 pages
and will include all your answers.
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