【单选题】As he isn’t here, I ________ that he must have missed the train.
【简答题】绿矾(FeSO 4 ?7H 2 O)是治疗缺铁性贫血的特效药.下面是以商品级纯度铁屑(含少量锡等杂质)生产绿矾的一种方法: 已知:在H 2 S饱和溶液中,SnS沉淀完全时溶液的pH为1.6;FeS开始沉淀时溶液的pH为3.0,沉淀完全时的pH为5.5. (1)检验所得绿矾晶体中是否含有Fe 3+ 的实验操作是______. (2)操作Ⅱ在溶液中用硫酸酸化至pH=2的目的是______;通入硫化氢至...
【单选题】听力原文:W: I must have told Mike five times not to forget the meeting. And he still missed it. M: Well, you know Mike everything's in one ear and out the other. Q: What can be inferred about Mike? (16)
A.
Mike doesn't always listen.
B.
Mike's never missed a meeting.
C.
Mike had to attend another meeting.
D.
Mike has an ear infection.
【简答题】硫酸亚锡(SuSO 4 )是一种重要的硫酸盐,广泛应用于镀锡工业。某研究小组设计SnSO 4 制备路线如下: 查阅资料: I.酸性条件下,锡在水溶液中有Sn 2+ 、Sn 4+ 两种主要存在形式,Sn 2+ 易被氧化。 II.SnC1 2 易水解生成碱式氯化亚锡[Sn(OH)Cl]。 回答下列问题: (1)SnC1 2 粉末需要加浓盐酸进行溶解,请用化学方程式说明原因_______________...
【判断题】Improving your study habits means having better learning techniques
【简答题】利用柱面坐标计算下列三重积分: (1),其中Ω是由上半球面与旋转抛物面z=x2+y2所围成的闭区域.利用柱面坐标计算下列三重积分:
【单选题】He must have missed the train, otherwise he _________ then.
B.
would have arrived here
【单选题】在换填施工中,砂填料应采用中、粗、砾砂,不含草根、垃圾等杂质,其含泥量不得大于( )。
【单选题】You've made some progress in your study.But it still remains ().