Question

Consider the titration of 20.0mL of 0.300M acetic acid, HAc, with 0.150M NaOH solution. Ka=1.75*10^-5

HAc + NaOH ---> NaAc + H2O

What is the composition of the solution at the equivalence point of the titration? Give both the formula of the compound and its concentration.

Calculate the pH at the equivalence point of the titration.

Answer 1

20*0.300 = x mL*0.150
Solve for x mL = 40 mL
Total volume at equivalence point is 40 + 20 = 60 mL
HAc + NaOH ==> NaAc + H2O
So the solution at the equivalence point is sodium acetate, NaAc, and the concn is millimols/mL = (20*300)/60 mL = ? = approx 0.1 The pH at the equivalence point is determined by the hydrolysis of the acetate ion.
..........Ac^- + HOH => HAc + OH^-
I.........0.1...........0......0
C........-x.............x......x
E......0.1-x............x......x

Kb for Ac^- = (Kw/Ka for HAc) = (x)(x)/(0.1-x)
Solve for x = (OH^-) and convert to pH.

Answer 2

Thank you so much. You cleared things up.