【单选题】下列各组混合物的分离或提纯方法不正确的是 [ ]
A.
用过滤的方法分离Fe(OH) 3 和FeCl 3 溶液的混合物
B.
用结晶法提纯NaCl和KNO 3 混合物中的KNO 3
【单选题】在MIS开发的生命周期法中,下列步骤中不属于系统分析阶段的是()
【简答题】()是分离液体均相混合物或液态均相气体混合物的操作。
【多选题】在MIS开发的生命周期法中,下列步骤中属于系统分析阶段的是()
【单选题】Many a young person tells me he wants to be a writer. I always encourage such people, but I also explain that there's a big difference between 'being a writer' and writ-ing. In most cases these indivi...
A.
warn young people of the hardships that a successful writer has to experience
B.
advise young people to give uptheir idea of becoming a professional writer
C.
show young people it's unrealistic for a writer to pursue wealth and fame
D.
encourage young people to pursue a writing career
【简答题】为下列混合物的分离或提纯提供正确的方法: (1)分离饱和食盐水和沙子的混合物______; (2)分离水和汽油的混合物______; (3)分离四氯化碳(沸点为76.75℃)和甲苯(有机溶剂,与CCl 4 互溶.沸点为110.6℃)的混合物______; (4)从碘的水溶液里提取碘______; (5)从食盐水中提取氯化钠______.
【简答题】自由基连锁反应分为链引发、链传递()三个阶段。 A链缩合 B链终止 C链增长 D链裂解
【单选题】在管理信息系统结构化生命周期法中,不属于系统分析阶段的是()。