A titration is performed using by adding 0.100 M NaOH to 40.0 mL of 0.1 M
HA (Ka is 1.0 x 10-5.).
a) Calculate the pH before addition of any NaOH.
Answer:
This first calculation is asking for the pH of the solution of the weak acid
before adding any base. The concentration of the HA before adding base is 0.100
M. For this first calculation we do not care what volume of the acid we have.
All we need to do is solve for the pH of a weak acid. Solving for the pH of
a weak acid requires setting up an ICE table for the weak acid;
|
HA(aq)
|
--->
|
H+(aq)
|
A-(aq)
|
I
|
0.100 M
|
|
~ 0
|
0
|
C
|
- x
|
|
+ x
|
+ x
|
F
|
0.100 - x
|
|
+ x
|
+ x
|
We can see this point on the titration curve (as point 2a).
