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问题 选择题

将等体积的苯、溴水和NaOH溶液在试管中充分混合后静置．下列图示现象正确的是（　　）

A．

B．

C．

D．

答案

苯是非极性分子的溶剂，溴是非极性分子的溶质，水是极性分子的溶剂，所以溴易溶于苯而不易溶于水，即溴在苯中溶解度比水中大，且水和苯不互溶，且水的密度大于苯的密度，溴水和氢氧化钠反应Br2+2NaOH=NaBr+NaBrO+H2O溴水褪色，故将等体积的苯、溴水和NaOH溶液在试管中充分混合后静置，上层橙黄色为溴的苯溶液，在水的上层，部分溴会与下层的NaOH反应，下层接近无色所以下层液体体积较大，从图象上看，C正确．

故选C．

单项选择题

酸性电位水除了有强氧化还原电位外，还溶解有（）。

A.1～5ppm氧和3～4mg／L活性氯

B.5～10ppm氧和3～4mg／L活性氯

C.10～50ppm氧和30～40mg／L活性氯

D.50～100ppm氧和30～40mg／L活性氯

E.100～500ppm氧和30～40g／L活性氯
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单项选择题

The purpose of the requirements definition phase is to produce a clear, complete, consistent, and testable (46) of the technical requirements for the software product.
During the requirements definition phase, the requirements definition team uses an iterative process to expand a broad statement of the system requirements into a complete and detailed specification of each function that the software must perform and each (47) that it must meet. The starting point is usually a set of high-level requirements from the (48) that describe the project or problem.
In either case, the requirements definition team formulates an overall concept for the system and then defines (49) showing how the system will be operated, publishes the system and operations concept document, and conducts a system concept review (SCR).
Following the SCR, the team derives (50) requirements for the system from the high-level requirements and the system and operations concept. Using structured or object-oriented analysis the team specifies the software functions and algorithms needed to satisfy each detailed requirement.

A．function

B．definition

C．model

D．statement
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