【已知】H3AsO4:pKa1 = 2.20,pKa2 = 7.00,pKa3 = 11.50【滴定突越】有2个:可以实现分步滴定。计量点:1、pH = 1/2(pKa1+ pKa2)= 2.20/2+ 7.00/2 = 4.60; 即 pH = 4.602、pH =1/2(pKa2+ pKa3)= 7.00/2+11.50/2 = 9.25; 即 pH = 9.25