How many moles of NaOH must be added to 1.0 L of 1.4 M HC2H3O2 to produce a solution buffered at each pH?

Question

(a) pH = pKa mol
(b) pH = 3.07 mol
(c) pH = 5.15 mol

Answer 1

Use the Henderson-Hasselbalch equation.
First find moles acetic acid. M x L = moles.
.......CH3COOH + OH^- ==>CH3COONa + H2O
start...moles.... 0.......0
change..-x........+x........+x
final..moles-x.....0......0+x

Then substitute into the HH equation and solve for x. After, I always like to check it by calculating the moles acetate and moles acetic acid remaining, plug into the HH equation and see if it gives the correct pH.