单项选择题
用K2Cr2O7滴定Fe2+,在化学计量点时,有关离子浓度的关系是()
A.A B.B C.C D.D
A.0.2g左右 B.0.2g~0.4g C.0.4g~0.8g D.0.8g~1.6g
A.[NH3]=0.20mol/L B.[NH3]+[Ag(NH3)+]+[Ag(NH3)2+]=0.20mol/L C.[NH3]+[Ag(NH3)+]+2[Ag(NH3)2+]=0.20mol/L D.[NH3]+[Ag(NH3)+]+2[Ag(NH3)2+]+[NH4+]=0.20mol/L