问题 问答题 简答题

提高化学反应鉴别法专属性的方法有哪些?

答案

参考答案:

慎重选用专属性不好的化学反应;在分析前对样品进行分离、精制,除去干扰鉴别反应的物质;选择专属性较强的检测试剂;采用阴性对照试验和阳性对照试验加以验证,从而保证检测的专属性和灵敏度。

阅读理解

阅读理解。

     Jeff Keith has only one leg. When he was 12 years old, Jeff had cancer (癌症). Doctors had to cut off

  most of his right leg.

     Every day Jeff puts on an artificial leg (假腿). With the plastic artificial leg Jeff can ride a bicycle, swim,

  and play soccer. He can also run.

     Jeff made a plan with his friends who had plastic legs, too. They decided to run across America.

     When he was 22 years old, Jeff Keith ran across the United States from the east to the west. He

 started running in Boston. Seven months later, he stopped running in Los Angeles. He ran 3,200 miles.

 Jeff stopped in cities on the way to Los Angeles. In every city people gave Jeff money. The money was

  not for Jeff, but for the American Cancer Society.

     Jeff is disabled, but he can do many things. He is studying to be a lawyer (律师). Jeff says, "People can

  do anything they want to do. I want people to know that. I ran not only for disabled people. I ran for

 everybody."

1. Jeff's right leg was cut off because he had _____.

    A. TB(肺结核)          

    B. an accident

    C. cancer             

    D. a serious injury

2. From the passage we know that Boston is _____.

    A. in the west              

    B. half between the east and west

    C. near Los Angeles           

    D. in the east

3. It took Jeff _____ to run from Boston to Los Angeles.

    A. about four and a half months    

    B. over two hundred days

    C. almost twenty-five weeks      

    D. less than half a year

4. The underlined word "disabled" means _____.

    A. 优秀的                  

    B. 劳累的

    C. 残疾的                  

    D. 无能为力的

5. The fifth passage tells us that _____.

    A. people should give him more money

    B. people can do anything they want to do

    C. some disabled men will become lawyers  

    D. disabled people also can run

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