问题 选择题

下列叙述中,正确的是

A.39K40Ca2微粒中的电子数不相等而中子数相等

B.D2和He在同温同压时,若体积相等,则质量相等

C.同一元素的各种同位素的物理性质、化学性质均相同

D.两个质子数和电子数都相等的微粒一定是同种元素

答案

答案:B

39K40Ca2微粒中的电子数和中子数分别为18和20、18和20,因此A不正确。等温等压时体积之比是物质的量之比,D2和He的摩尔质量都是4g/mol,所以B正确。同一元素的各种同位素的物理性质不同、化学性质相同,C不正确。元素是指具有相同核电荷数(即核内质子数)的一类原子的总称,而微粒的范围很广泛,可以是分子或是原子团等,D不正确。答案是B。

阅读理解

阅读理解。

                                                         How I Turned to Be Optimistic

     I began to grow up that winter night when my parents and I were returning from my aunt's house, and

my mother said that we might soon be leaving for America. We were on the bus then. I was crying, and

some people on the bus were turning around to look at me. I remember that I could not bear the thought

of never hearing again the radio program for school children to which I listened every morning.

     I do not remember myself crying for this reason again. In fact, I think I cried very little when I was

saying goodbye to my friends and relatives. When we were leaving I thought about all the places I was

going to see-the strange and magical places I had known only from books and pictures. The country I was

leaving never to come back was hardly in my head then.

     The four years that followed taught me the importance of optimism, but the idea did not come to me at

once. For the first two years in New York I was really lost-having to study in three schools as a result of

family moves. I did not quite know what I was or what I should be. Mother remarried, and things became

even more complex for me. Some time passed before my stepfather and I got used to each other. I was

often sad, and saw no end to "the hard times."

     My responsibilities in the family increased a lot since I knew English better than everyone else at home.

I wrote letters, filled out forms, translated at interviews with Immigration officers, took my grandparents

to the doctor and translated there, and even discussed telephone bills with company representatives.

     From my experiences I have learned one important rule: Almost all common troubles eventually go away!

Something good is certain to happen in the end when you do not give up, and just wait a little! I believe that

my life will turn out all right, even though it will not be that easy.

1. How did the author get to know America?

A. From her relatives

B. From her mother

C. From Books and pictures

D. From radio programs

2. Upon leaving for America the author felt _____.

A. confused

B. excited

C. worried

D. amazed

3. For the first two years in New York, the author _____.

A. often lost her way

B. did not think about her future

C. studied in three different schools

D. got on well with her stepfather

4. What can we learn about the author from Paragraph 4?

A. She worked as a translator

B. She attended a lot of job interviews

C. She paid telephone bills for her family

D. She helped her family with her English

5. The author believes that _____.

A. her future will be free from troubles

B. it is difficult to learn to become patient

C. there are more good things than bad things

D. good things will happen if one keeps trying

判断题