问题 选择题

升高温度时,化学反应速率加快,主要原因是(   )

A.分子运动速率加快,使该反应物分子的碰撞机会增多

B.反应物分子的能量增加,活化分子百分数增大,有效碰撞次数增多

C.该化学反应的过程是吸热的

D.该化学反应的过程是放热的

答案

答案:B

题目分析:A.分子运动速率加快,使该反应物分子的碰撞机会增多,但是不是所有的分子间的碰撞都能发生化学反应。只有那些分子能量高的按照一定去向发生的碰撞才能发生化学反应。错误。B.升高温度时,反应物分子的能量增加,活化分子数增多,由于分子总数没有变化,所有活化分子百分数增大,有效碰撞次数增多。因此化学反应速率加快。正确。无论是放热反应还是吸热反应,当升高温度时,反应物分子的能量都增加,使一部分分子变为活化分子,活化分子百分数增大,有效碰撞次数增多,反应速率加快。C.D都是错误的。

阅读理解

第三部分 阅读理解(共20小题:每小题2分,满分40分)

阅读下列短文,从每题所给的四个选项(A、B、C和D)中,选出最佳选项,并在答

题卡上将该项涂黑。

Wishing to encourage her young son to make more progress on the piano,a mother took her boy to a Paderewski concert. After they were seated,the mother spotted a friend in the audience and walked down the aisle to greet her. Seizing the opportunity to explore the wonders of the concert hall,the little boy rose and eventually found his way through a door marked "NO ADMITTANCE.” When the house lights dimmed and the concert was about to begin, the mother returned to her seat and discovered that the child was missing.

Suddenly,the curtains parted and spotlights focused on the impressive Steinway on stage. To her horror,the mother saw her little boy sitting at the keyboard,innocently picking out Twinkle,Twinkle Little Star.

At that moment, the great pianist made his entrance, quickly moved to the piano, and whispered in the boy's ear, "Don't quit. Keep playing." Then leaning over, Paderewski reached down with his left hand and began filling in a bass part. Soon his right arm reached around to the other side of the child and he added a melody. Together, the old master and the young beginner transformed a frightening situation into a wonderfully creative experience. The audience was amazed and, as it finished, they cheered.

That's the way it is in life. What we can accomplish on our own is hardly noteworthy. We try our best, but the results aren't exactly graceful flowing music. But when we put our trust in the hands of a Greater Power, our life's work can be truly beautiful. Next time you set out to accomplish great feats, listen carefully. You can hear the voice of the Master, whispering in your ear, "Don't quit, keep playing.

56. The mother took her son to the concert so that the boy could _______.

A. be encouraged to be a brave man          B. become a famous pianist

C. be inspired to achieve more              D. be a great artist

57. The reason why the boy went to the piano was that

A. he was encouraged to explore  B. his mother forced him to have a look

C. be was invited to by the pianist           D. he was exploring the concert hall

58. What the famous pianist did at the beginning of the concert showed ________.

A. what a great pianist he was              B. what a skilled pianist he was

C. what an upright man he was               D. what a strong man he was

59. What did the author really want to tell us in the last paragraph?

A. Not being interrupted by others is important.

B. Life needs one's own effort combined with guidance and cooperation.

C. It is necessary for us to keep doing everything.

D. It is important for us to get help from a famous person.

单项选择题