用Ce4+滴定Fe2+,當(dāng)體系電位為0.68V時,滴定分?jǐn)?shù)為()
A.0 B.50% C.100% D.200%
A.濃HCl B.1mol/LNaOH C.1mol/LNa2SO4 D.1mol/LNH3·H2O