buffer solution chemistry

I am sorry that I have return my knowledge to my teacher
but

you know HF is not a strong acid, it is weak acid, thought it is again special that its solubility can go insanely high when the concentration is very high due to hydrogen bond (not important here)

http://en.wikipedia.org/wiki/Hydrofluoric_acid

CsOH is a strong base

and you know weak acid and its congegate base, when presence together, they can oppose the change in pH by the reaction of both
F- + H+ --> HF
HF + OH- --> H2O + F-

Ka = [H+][F-]/[HF]
by http://www.bpc.edu/mathscience/chemistry/table_of_monoprotic_acids.html
Ka = 7.2x10^-4
if only strong acid, when you add strong base so that H+ reduce concentration in solution by 0.01M, you use that equimolar strong base
lets say if you have 0.1M of HF and CsF in that solution, and add the same amount of strong base
before [H+] = Ka, pH=3.14
after: [H+] = Ka/1.22, pH=3.23
change of concentration of H+ is only 1.356x10^-4 only
Ka (1-1.22)

I may be wrong, please ignore my answer if it is

長知識了哦～～，thx～～～