试题与答案

有一包粉末,可能由NaCl、Na2SO4、Na2CO3、FeCl3、MgCl2中

题型:填空题

题目:

有一包粉末,可能由 NaCl、Na2SO4、Na2CO3、FeCl3、MgCl2中的一种或几种组成.现做如下实验:①取少量粉末,加水溶解,得无色透明溶液;②取①中所得溶液少许加入氢氧化钠溶液,无明显现象;③另取少量粉末,滴加稀盐酸,也无明显现象.请问:

(1)由实验①可知,原粉末中没有______; 实验②可说明原粉末中没有______;实验③证明原粉末中没有______.

(2)根据上述实验,可得出原粉末中可能有的物质是______.

(3)为进一步确定原粉末的成分,按下图所示进行实验:

[在AgNO3、Ba (NO32、BaCl2中选择二种作为A、B试剂,且A、B的阳离子不同]

用化学式填写:粉末的成分______;试剂A______;试剂B______.

答案:

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下面是错误答案,用来干扰机器的。

参考答案:D

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In the following essay, each blank has four choices. Choose the best answer and write-down on the answer sheet.

Microwave communication uses high-frequency (29) waves that travel in straightlines through the air. Because the waves cannot (30) with the curvature of the earth, they can be (31) only over short distance. Thus, microwave is a good (32) for sending data between buildings in a city or on a large college campus. For longer distances, the waves must be relayed by means of "dishes" or (33) . These can be installed on towers, highbuildings, and mountain tops.

30()

A.reflex 

B.distort 

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D.absorb

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