Kemi- protolyse

Skal jeg ikke sige -log(0,5 M) for at beregne pH?

alment for en ikke stærk syre S
med protolysegraden 0 < α < 1
og formel koncentration c
gælder:

                                                           S _(aq)   +   H₂O _(l)   <--->   B _(aq)   +   H₃O⁺ _(aq)
              ligevægtsmolariteter:          (1-α)·c                                 α·c            α·c    

med
              ligevægtsbrøken
                                                                     [B] • [H₃O⁺]
                                                                    ----------------- = K_s
                                                                            [S]

.           
                                                                      (α·c)²
                                                                    ---------- = K_s
                                                                     (1-α)·c

                                                                            α²
                                                                    c • -------- = 10^-pK_s
                                                                          1 - α

a)

     som for 0,50 M HSO₄^- med pK_s = 1,92
     giver
                                                                                  α²
                                                                    0,50 • -------- = 10^-1,92  og  0 < α < 1
                                                                               1 - α

                                                                     α = 0,144 = 14,4%
 

b)
     Der tilsættes 400 mL vand:
                                                    fortyndingsfaktor f = ((300 mL) + (400 mL)) / (300 mL) = (7/3)

     Den fortyndede syres
     molaritet
                                                   c_fort = c / f = (0,50 M) / (7/3) = 0,21 M

.

     Den fortyndede syres
     protolysegrad:

                                                                                  α²
                                                                    0,21 • -------- = 10^-1,92  og  0 < α < 1
                                                                               1 - α

                                                                     α = 0,212 = 21,2%

se evt.
https://www.studieportalen.dk/Forums/Thread.aspx?id=1425177

men her mindskes c
hvorfor
                α øges  da 10^-pK_s = K_s er konstant:
                                                                            α²
                                                                    c • -------- = 10^-pK_s
                                                                          1 - α

···················

                                                                             α²
                                                                         --------  øges når
                                                                          1 - α

tælleren α² øges når α øges                                                       
nævneren (1 - α) mindskes når α øges
 

alment for en ikke stærk syre S  -->  alment for en ikke stærk monohydron syre S