问题 问答题 简答题

何谓理想同位素交换反应?它有何特点?

答案

参考答案:

理想同位素交换反应:指不考虑同位素效应的同位素交换反应。

特点:

⑴平衡常数kp=1,正、逆反应速率常数相等;

⑵同位素交换无热效应,QT=0;

⑶正、逆反应的活化能相等;

⑷同位素交换反应的平衡常数与温度无关;

⑸同位素交换反应不伴随浓度(不含同位素浓度)的变化。

多项选择题
阅读理解

阅读理解。

     I really love my job because I enjoy working with small children and like the challenges and awards

from the job. I also think my work is important. There was a time when I thought I would never have that

sort of career (职业).

     I wasn't an excellent student because I didn't do much schoolwork. In my final term I started thinking

what I might do and found I didn't have much to offer. I just accepted that I wasn't the type to have a

career.

      I  then found myself a job, looking after two little girls. It wasn't too bad at first. But the problems

began when I agreed to live in, so that I would be there if my boss had to go out for business in the

evening. We agreed that if I had to work extra hours one week, she'd give me time off the next. But

unfortunately, it didn't often work out. I was getting extremely tired and fed up, because I had too many

late nights and early mornings with the children.

     One Sunday, I was in the park with the children, and met Megan who used to go to school with me. I

told her about my situation. She suggested that I should do a course and get a qualification (资格证书) if

I wanted to work with children. I didn't think I would be accepted because I didn't take many exams in

school. She persuaded me to phone the local college and they were really helpful. My experience

counted for a lot and I got on a part-time course. I had to leave my job with the family, and got work

helping out at a kindergarten.

     Now I've got a full-time job there. I shall always be thankful to Megan. I wish I had known earlier

that you could have a career, even if you aren't top of the class at school.

1. When staying with the two girls' family, the author ________.

A. was paid for extra work            

B. often worked long hours

C. got much help from her boss        

D. took a day off every other week

2. Why did the author leave her first job?

A. She found a full-time job.              

B. She was fed up with children.

C. She decided to attend a part-time course.  

D. She needed a rest after working extra hours.

3. What has the author learned from her own experiences?

A. Less successful students can still have a career.  

B. Qualifications are necessary for a career.

C. Hard work makes an excellent student.        

D. One must choose the job she likes.