He ________ to school last week.[ ]
A. go
B. went
C. goes
D. going
答案:B
将3.48克Fe3O4完全溶解在100mL1mol/LH2SO4中,然后加入K2Cr2O7溶液25mL,恰好使溶液中Fe2+全部转化为成Fe3+,Cr2O72-离子全部还原为Cr3+。则K2Cr2O7溶液的摩尔浓度为
A.0.05mol/L
B.1.0mol/L
C.0.2mol/L
D.0.3mol/L
与疏水器的设计排水量有关的参数,是下列哪几项
A.疏水器阀孔直径
B.疏水器前后压差
C.疏水器选择倍率
D.疏水器的背压