Ka= 1,8•10^-5
pKa = - log(Ka) = 4,74
Equivalence volume :
Ca x Va = Cb x Vb
Vb = Ca x Va / Cb
Vb = 0,35 x 52,0 / 0,40
Vb = 45,5 mL
21,0 mL < 45,5 mL
. . . then :
pH = pKa / 2 - log( (Ca x Va - Cb x V) / (Va + V)) / 2
pH = pKa / 2 - log( (0,35 x 52 - 0,40 x 21) / (52 + 21)) / 2
pH = 3,24
