Ph question?

Question

A certain weak acid,HA , with a Ka of 5.61 *10^-6 ,is titrated with NaOH . A solution is made by mixing 7.00 millimoles of HA and 1.00 millimoles of base and the resulting pH is 4.47. More strong base is added until the equivalence point is reached. What is the pH of this solution at the equivalence point if the total volume is 80.0 mL ?

Please try and show all steps bc i have a test tom. Thanks in advance!!!!!

Answer 1

I'll start you off. The first bit is about making a buffer solution.
[H+] = Ka x [acid]/[base]

Raise 10 to the power of -4.47 to get [H+].

Adding 1mmol of strong base to 7mmol of HA gives 6mmol of HA and 1mmol of A-.