Exercise 8 | Buffers and Titration of Acids and Bases
General Chemistry 3 - Exercise 8
Consider a solution initially containing 0.40 mol fluoride anion and 0.30 mol of hydrogen fluoride.
What is the pH after addition of 0.20 mol of HCl to this solution?
Data: pKa (HF/F-) = 3.14
The titration equation is:
Reaction: F- + H3O+ HF + H2O
After adding 0.20 mol of HCl:
nF-,0 = 0.40 mol
nH+,0 = 0.20 mol
H3O+ is the limiting reagent.
nF- = nF-,0 - nH+,0 = 0.20 mol
nHF = nHF,0 + nH+,0 = 0.50 mol
Henderson-Hasselbalch equation can be used:
pH = pKa + log
pH = 3.14 + log
pH = 2.74