How Does Adding Sodium Citrate Affect the pH of a Citric Acid Solution?

[sam.]

What is the pH change of a 0.270 M solution of citric acid (pKa = 4.77) if enough sodium citrate is added to make the final concentration of the common citrate ion 0.145 M?

Okay so first I did an ice-table using the equation:
citric acid + water <--> hydronium + citric ion
Using an inital concentration of 0.270 for citric acid and then just solving for x using the Ka value and I got pH = 2.67 (which is the initial pH).
Now I'm having a problem with how to find the final pH. I think you're supposed to set up another ice table but I'm not too sure what values are supposed to be my initial concentrations. Any help would be greatly appreciated!

 

[lightarrow]

What is the pH change of a 0.270 M solution of citric acid (pKa = 4.77) if enough sodium citrate is added to make the final concentration of the common citrate ion 0.145 M?

Okay so first I did an ice-table using the equation:
citric acid + water <--> hydronium + citric ion
Using an inital concentration of 0.270 for citric acid and then just solving for x using the Ka value and I got pH = 2.67 (which is the initial pH).
Now I'm having a problem with how to find the final pH. I think you're supposed to set up another ice table but I'm not too sure what values are supposed to be my initial concentrations. Any help would be greatly appreciated!

HA + H2O <--> H3O+ + A-

[HA] = 0.270 - x
[H3O+] = x
[A-] = 0.145

[H3O+]*[A-]/[HA] = Ka = 10^(-4.77)

--> x*0.145/(0.270 - x) = 10^(-4.77)

--> x = 3.16*10^(-5) --> pH = 4.50