CH3COONa + HCl ------------> CH3COOH + NaCl
____X________Y_________________0_______/___
___X-Y_______0_________________Y.

t.c.:

[H+] = 10^-5 = 1.8*10^-5 * Y / (X-Y)

Inoltre:

X – Y +Y = X = 0.100

=> 10^-5 = 1.8*10^-5 * Y / (0.100-Y) =

=> 0.556 *(0.100-Y) = Y

=> 0.0556 – 0.556Y = Y

=> Y = 0.0556 / 1.556 = 3.57*10^-2

X = 0.100mol/L => 0.100mol/L * 0.250L = 0.0250mol di CH3COONa

0.0250mol * 118.06g/mol = 2.95g di CH3COONa

Y = 3.57*10^-2mol/L
=> 3.57*10^-2mol/L * 0.250L = 0.100mol/L * V

V = 8.93*10^-2L => 89.3mL (questo valore è doverso...)