问题 选择题

下列说法正确的是(  )

A.活化分子之间的碰撞即为有效碰撞

B.使用催化剂能降低活化能,增加活化分子百分数

C.增大压强不能降低活化能,但能增加活化分子百分数

D.活化能的大小决定了反应能否自发进行

答案

A.活化分子之间的碰撞发生化学反应时为有效碰撞,否则不是,故A错误;

B.催化剂能降低活化能,增大活化分子的百分数,从而加快反应的速率,故B正确;

C.增大压强不能增加活化分子的百分数,使反应速率增大原因是活化分子的浓度增大,但百分数不变,故C错误;

D.反应能否自发进行取决于反应的焓变和熵变,活化能的大小影响反应速率的大小,故D错误.

故选B.

阅读理解

阅读理解。

        In England, afternoon tea, taken between four and five, is the most informal (非正式) meal of the day.

If you are a friend of the family, you may drop in for tea without an invitation or telling that you are coming.

Very often it is not served at a table. The members of the family and visitors take tea in the sitting-room.

Each person has a cup and saucer (托盘), a spoon (汤匙) and a small plate for bread-and-butter and cake.

By the way, do not help yourself to cake first; bread-and-butter first, then cake if there is any. Another piece

of advice: Do not put more than one piece of bread or cake on your plate at the same time.

1. Afternoon tea is usually served with _______.

A. tea only

B. tea and some food

C. tea, dessert and meat

D. cake and bread

2. If you want to have afternoon tea in a friend's home, _______.

A. it is necessary for you to send a message

B. you should wait for his invitation

C. it is impolite for you to go there without taking anything with you

D. it is unnecessary for you to call him or send a message

3. In the passage, "drop in" means "_______".

A. pay an informal visit

B. fall down

C. drink at a friend's home

D. break

4. It's impolite for you _______.

A. help yourself to cake first

B. share a cup with your friend

C. put more than one piece of bread or cake on your plate once

D. all of the above

5. Which of the following is NOT true?

A. Afternoon tea is often taken in the sitting-room.

B. The members of the family often share a cup and saucer, a spoon, etc.

C. Afternoon tea is usually taken between lunch and supper.

D. Help yourself to bread-and-butter before cake if there is any.

选择题