问题 选择题

下列表示对应化学反应的离子方程式或化学方程式正确的是(    )

A.稀硝酸和过量的铁屑反应:Fe+4H++ NO3=Fe3++NO↑+2H2O

B.碳酸钠溶液水解的离子方程式:CO32+2H2OH2CO3+2OH

C.氢气的燃烧热为285.8 kJ/mol,则表示氢气燃烧的热化学方程式为:2H2(g) + O2(g) = 2H2O(g);△H =" –571.6" kJ/mol

D.浓盐酸与MnO2共热制氯气:MnO2+4H+2ClMn2+Cl2↑+2H2O

答案

答案:D

题目分析:A不正确,铁过量时生成的是亚铁离子;B不正确,CO32水解是分步进行的;燃烧热是在一定条件下,1mol可燃物完全燃烧生成稳定的氧化物时所放出的热量,因此C不正确,所以正确的答案选D。

点评:判断离子方程式正确与否的方法一般是:(1)检查反应能否发生。(2)检查反应物、生成物是否正确。(3)检查各物质拆分是否正确。(4)检查是否符合守恒关系(如:质量守恒和电荷守恒等)。(5)检查是否符合原化学方程式。

单项选择题
阅读理解

C

  Once upon a time,there was a wonderful old man who loved everything on the land——animals and plants.

  One day while walking through the woods,the old man found a cocoon of a butterfly. He took it home. A few days later,a small opening appeared;he sat and watched the butterfly for several hours as it struggled to force its body through that little hole. Then it seemed to stop making any progress. It appeared as if it had gotten as far as it could and it could go no farther. Then the man decided to help the butterfly,so he took a pair of scissors and cut the remaining bit of the cocoon. The butterfly then came out easily.

  But it had a swollen body and small,shriveled(枯萎的)wings. The man continued to watch the butterfly because he expected that,at any moment,the wings would enlarge and expand to be able to support the body,or they would be smaller. Neither happened! In fact,the butterfly spent the rest of its life crawling around with a swollen body and shriveled wings. It never was able to fly.

  What the man in his kindness and hurry did not understand was that the struggle required for the butterfly to get through the tiny opening was nature’s way of forcing fluid from the body of the butterfly into its wings so that it would be ready for flight once it achieved its freedom from the cocoon.

  Sometimes struggles are exactly what we need in our life. If we were allowed to go through our life without any difficulties,it would cripple(使无能)us. We would not be as strong as what we could have been. And we could never fly.

59.The old man cut the cocoon in order to__________.

A.kill the butterfly

B.play with the butterfly

C.make the butterfly come out easily

D.have the butterfly

60.The reason why the butterfly could not fly is that__________.

A.the old man broke its wings

B.it was too small

C.newly born butterflies can’t fly

D.it came out of its cocoon without enough struggle

61.What can we know from the passage?

A.That old man was fond of everything except the butterfly.

B.It was the old man that stopped the butterfly flying.

C.The old man realized his mistake.

D.It’s not hard for the butterfly to come out of the cocoon.

62.What does the author want to tell us by writing the passage?

A.We should help others.

B.Without others help we can still succeed.

C.Struggles in our life can make us stronger.

D.Butterflies can fly without people’s help.