posted by Waleed .
What is the volume of a solution of 0.5 M NaOH that must be added to adjust the pH
from 4 to 9 in 20 mL of a 100 mM solution of phosphoric acid?
Its been about 4 years since I've done this stuff. All I know is the pKa of phosphoric acid is 2.15 and I'm assuming In need to use the Henderson-Hassleback equation.