用莫尔法(AgNO3滴定X-)测定样品中的Cl-，若样品中含有Fe3+、A13+等离子，应采用何种方法消除其干扰()。
A. 掩蔽法
B. 沉淀分离法
C. 分步沉淀法
D. 返滴定法
查看答案
This passage can be entitled____.
A Silly Question
B. Don't Trouble a Busy Man
C. What Are Good Greetings
D. George Bernard Shaw's Reply
【C6】
A. observable
B. differentiate
C. recognizable
D. accountable
在气相色谱分析某组分时，已知其保留值为11 min，空气出峰时间为0．5 min，则该组分由于溶解或吸附于固定相较不溶解或不被吸附在色谱柱中多滞留的时间为()。
A. 5．5 min
B. 10．5 min
C. 11．5 min
D. 22 rain
According to the passage, freedom can not be easily given since_____.
A. it is in not what workers care about
B. it has nothing to do with increasing productivity
C. freedom will do harm to the management
D. machines in modern factories must be organized in a fixed way
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