题目

--Do you believe there are aliens? --I'm afraid not．I don't think aliens           in space． A．can find               B．can be found           C．can be founded       D．can't be found 答案：B现有化学试剂：浓溶液、生石灰及常用于燥剂，制取干燥，纯净的氨气． (1)请从下面的仪器中选择制取氨气的发生装置．(要求使用仪器最少、合理)________(写序号) (2)写出用浓溶液与生石灰反应制取氨气的理由． ______________________________________________________________ ______________________________________________________________ (3)实验操作时，关键之处是______________________________________ 理由是________________________________________________________ (4)干燥氨气应选用的干燥剂是____________________________________