In: Chemistry
In an acid base titration experiment, 50.0 ml of a 0.0500 m solution of acetic acid ( ka =7.5 x 10^-5) was titrated with a 0.0500 M solution of NaOH at 25 C. The system will acquire this pH after addition of 20.00 mL of the titrant:
Answer is 4.581
Please show all work
No. of moles of acetic acid initially;

No of moles of NaOH added;

Now, draw the ice table for the reaction,
CH3COOH![]()  | 
|
| Initially | 2.5*10-3mol | 
| When NaOH is added | 2.5*10-3-1*10-3 mol | 
| Finally | 1.5*10-3 mol | 
The conentration of acetic acid= 1.5/(50+20)=0.0214 M
Consider the dissociation of acetic acid;
CH3COOH![]()  | 
CH3COO- + | H+ | 
| 0.0214 M | 0 | 0 | 
| 0.0214-X | X | X | 

As x <<< 0.0214, we assume that 0.00214=0.00214-x.



Now, calculate the pH of the system using the fllowing equation,



