题干

下列实验方案中,能达到目的是(  )

选项

实验目的

实验方案

A

分离氯化钙和氯化镁的混合溶液

加适量氢氧化钙溶液,充分反应后过滤

B

检验氢氧化钠溶液已部分变质

取少量溶液,滴加足量的氯化钡溶液,过滤,向滤液中滴加酚酞溶液

C

除去二氧化碳中混有的一氧化碳

将混合气体通过灼热的铜网

D

粗略测定空气中氧气的含量

用硫粉代替红磷在空气中燃烧

A:A

B:B

C:C

D:D

上一题 下一题 0.0难度 选择题 更新时间:2015-09-23 06:28:41

答案(点此获取答案解析)

B

同类题2

完形填空
       Once upon a time there was a little orphan(孤儿) who always wished that he could fly like a bird. It was very   1   for him to understand why he could not fly.
  There was another little boy who was crippled(瘸子). One day the orphan came to a park, where he saw the little crippled boy   2   in the sand alone.
  He ran over to the little crippled boy and asked him if he had ever wanted to fly like a bird.
  “No, ” he said. “  3  I've been thinking about what it would be like to walk and run like   4  .”
  “That is very sad, ” said the little orphan. “Do you think we could be friends?”
  “Sure, ”said the little crippled boy.
  The two little boys played for hours.  5 of them felt as lonely as they have been before. Then the little crippled   6 father came with a wheelchair to  7  his son. The little orphan ran over to him and said something into his ear.
  “That would be Okay, ”said the man.
  The little orphan ran back to his friend and said, "You are my only friend and I   8 I could do something to make you walk and run like others. 9  , I can't. But there is something that I can do for you."
  The little orphan boy turned10  and told his friend to slide onto his back. Then he began to run across the grass. He ran faster and faster,  11 the little crippled boy on his back.
The father began to cry with tears as his son shouted at the top of his   12 , "I am FLYING! Daddy, I am FLYING!"
That's the little orphan who helped the crippled boy  13 the dream to fly in his life and moved the father.14 he didn't know the reason why he could not fly, he helped another boy fly and harvested happiness from it. Let's always be ready to help others because helping others is helping   15 .