We ______ you were in trouble at that time otherwise we would have given you a hand. A. didn’t know B. havn’t known C. don’t know D. hadn’t known 答案:A6.用废弃的金属镁、铁、铜制取重要化工原料MgSO4的实验过程如下:请回答:(1)金属B是铜.(2)操作a的名称是过滤;在蒸发过程中需要使用玻璃棒,其作用是搅拌,防止局部温度过高造成液滴飞溅.(3)写出步骤②所涉及的化学反应方程式:Mg+H2SO4=MgSO4+H2↑;(4)实验步骤②中除了加入稀硫酸外,还可选用下列试剂a(填序号).a.硫酸铜溶液 b.氯化钠溶液 c.硝酸银溶液.