Thx for all replies.
HaXb means,for example,
H2SO4,a = 2,X = SO4 2-, b =1
CH3COOH, a = 1, X = CH3COO- , b=1
So,I can't substitute the above formula in the case KH3(C2O4)
And consider the equation
KH3(C2O4)2·2H2O + NaOH --> NaH3(C2O4)2 + 2H2O + KOH
so H3(C2O4)2 is an anion with charge 1-?
and the resultant solution is strongly alkaline?
I don't quite understand why neutralization will give out strong alkali(KOH),usually,weak acidic/weak alkaline or neutral salt is given out.