In: Chemistry
a 100ml sample of .20M HF is titrated with .10M KOH. determine Ph of solution after addition of 100ml of KOH.Ka is 3.5x10-4.
millimoles of HF = 100 x 0.20 = 20
millimoles of KOH = 100 x 0.10 = 10
HF + KOH --------------------> KF + H2O
20 10 0 0 ----------------------> initial
10 0 10 0 -----------------------> after reaction
in this mixture HF weak acid and KF salt remained . so it can form acidic buffer
pKa = -log Ka = -log(3.5x10^-4.) =3.46
For acidic buffer
Henderson-Hasselbalch equation
pH = pKa + log[salt/acid]
pH = pKa + log[salt/acid]
pH = 3.46 + log (10/10)
pH = 3.46