1. Na
2CO
3(s) --> 2 Na
+ (aq) + CO
32-(aq)
2. CO32-(aq) + H2O <=> HCO3-(aq) + OH-(aq)
3. begin 0,12 M 0 0
omzetting -x + x + x
evenwicht 0,12-x x x
4. Kb = [HCO3-][OH-] / [CO32-] = 2,1*10-4
5. c/Kb >100, dus x = [OH-] = wortel uit (0,12 * 2,1*10-4) = 0,00501 M
pOH = -log(0,00501) = 2,299
pH = 14,00 - 2,30 = 11,70 (2 decimalen, want concentratie gegeven in 2 significante cijfers)