问题 选择题

NA为阿伏加德罗常数,下列叙述正确的是

A.28gCO和N2混合气体中含有原子总数为2NA

B.标准状况下,22.4 L水所含的H2O分子数为NA

C.足量铜与1L 18mol·L-1浓硫酸反应可以得到SO2的分子总数为9NA

D.1mol Na与足量O2反应,生成Na2O和Na2O2的混合物,钠失去电子数为2NA

答案

答案:A

题目分析:A.一氧化氮和氮气都是双原子分子,而且摩尔质量也相同,所以原子总数是2NA

B.标准状况下,水是液体,所以22.4 L水的物质的量不是1mol,所含的H2O分子数也不是NA个;

C.足量铜与1L 18mol·L-1浓硫酸反应可以得到SO2的分子总数小于9NA,其中理论上只有一半的硫酸做氧化剂;

D.1mol Na与足量O2反应,生成Na2O和Na2O2的混合物,钠失去电子数为NA故选A。

点评:本题需要学生注意的是,气体摩尔体积应用时要注意:标况下,水是液态,不适用该公式。

阅读理解

阅读理解

     High school dropouts(辍学者)earn an average of $ 9 ,000 less per year than graduates. Now a

new study dispels a common belief why they quit. It’s much more basic than flunking out(不及格).

     Society tends to think of high school dropouts as kids who just can’t cut it. They are lazy  ,and

perhaps not two bright.So researchers were surprised when they asked more than 450 kids who

quit school about why they left.

    ''The vast majority actually had passing grades and they were confident that they could have

graduated from high school. “ John Bridgeland , the executive researcher said. About 1 million teens

leave school each year. Only about half of African-American and Hispanic(美籍西班牙的)

students will receive a diploma(证书)  ,and actually all dropouts come to regret their decision.

So , if failing grades don’t explain why these kids quit , what does? Again  ,John Bridgeland : “The

most dependable finding was that they were bored. “ They found classes uninteresting; they weren’t

inspired or motivated. They didn’t see any direct connection between what they were learning in the

classroom to their own lives , or to their career aspirations. "    

     The study found that most teens who do drop out wait until they turn sixteen , which happens to be

the age at which most states allow students to quit. In the US  ,only one state  ,New Mexico  ,has a

law requiring teenagers to stay in high school until they graduate. Only four states: California ,

Tennessee , Texas and Utah , plus the District of Columbia , require school attendance until age 18 ,

no exceptions , another researcher  ,says raising the compulsory attendance age may be one way to

keep more kids in school.

      ''As these dropouts look back  ,they realize they’ve made a mistake. And anything that sort of

gives these people an extra push to stick it out and it through to the end , is probably helpful measure. ''   

     New Hampshire may be the next state to raise its school attendance age to 18. But critics say that

forcing the students unwilling to continue their studies to stay in school misses the point-the need for

reform. It's been called for to reinvent high school education to make it more challenging and relevant ,

and to ensure that kids who do stick it out receive a diploma that actually means something.

1. Most high school students drop out of school because         .

    A. they have failing grade          

    B. they take no interest in classes

    C. they are discriminated against    

    D. they are lazy and not intelligent

2. The underlined words  “stick it out “ probably means “         ''.

    A. complete schooling        

    B. solve the problem

    C. love having classes        

    D. believe in themselves

3. In the last paragraph , the writer is trying to          .  

    A. analyze the reason why students quit school

    B. suggest raising the compulsory attendance age

    C. raise awareness of reforming high school education

    D. wish to make laws to guarantee no education

4. From the passage  ,we can infer the following EXCEPT that         

    A. the grades of most dropouts at school were acceptable

    B. about 500 , 000 high school dropouts are black and Spanish

    C. classes don't appeal to dropouts

    D. on average dropouts cannot get good jobs

单项选择题