问题 选择题

某同学欲用蜡烛燃烧验证质量守恒定律,实验设计如下图所示。实验时用吸收剂将产生的水和二氧化碳进行彻底吸收。下列实验现象和分析错误的是

A.点燃蜡烛后天平指针向右偏转

B.蜡烛燃烧反应为氧化反应

C.此实验中生成CO2中的碳元素质量一定等于

参加反应蜡烛中碳元素质量

D.此实验中生成水中的氢元素质量一定等于参加反应蜡烛中氢元素质量

答案

 

题目分析:A选项点燃蜡烛后天平指针向右偏转是正确的叙述,热气体往上去产生浮力;B选项根据氧化反应的定义,蜡烛燃烧反应为氧化反应是正确的叙述 ;C选项是错误的叙述,氧气不充足时可能生成一氧化碳 ;D选项此实验中生成水中的氢元素质量一定等于参加反应蜡烛中氢元素质量,是正确的叙述,故答案选择C

单项选择题
阅读理解

四、阅读理解:(共20小题;每小题1.5分,满分30分)

A

Steve and Yaser first met in their chemistry class at an American university. Yaser was an international student from Jordan. He was excited to get to know an American. He wanted to learn more about American culture. Yaser hoped that he and Steve would become good friends.

At first, Steve seemed very friendly. He always greeted Yaser warmly before class. Sometimes he offered to study with Yaser. He even invited Yaser to have lunch with him. But after the term was over, Steve seemed more distant. The two former(以前的) classmates didn’t see each other very much at school. One day Yaser decided to call Steve. steve didn’t seem very interested in talking to him. Yaser was hurt by Steve’s change of attitude. “Steve said we were friends,” Yaser complained. “And I thought friends were friends forever.”

Yaser is a little confused. He is an outsider(局外人) to American culture. He doesn’t understand the way Americans view friendship. americans use the word “friend” in a very general way. They may call both casual acquaintaneces(熟人) and close companions(伙伴) “friends”. americans have school friends, work friends, sports friends and neighborhood friends. These friendships are based on common interests.

Studies show that one out of five American families moves every year. American frienships develop quckly, and they may change just as quickly.

People from the United States may at first seem friendly. Americans often chat easily with strangers. They exchange information about their families, hobbies and work. They may smile warmly and say, “Have a nice day.” or “see you later.” schoolmates may say, “Let’s get together sometime.” But American friendliness is not always an offer of true friendship.

41. Why didn’t Yaser understand Steve was more was more distant with him when they were no longer in the same class?

A. Because Steve no longer likes Yaser.

B. Because they couldn’t see each other.

C. Because Yaser didn’t know american culture about friendship.

D. Because Yaer was a foreigner.

42. From the text we can find that American friendships ________.

A. develop quickly but change slowly           B. develop slowly and change slowly

C. develop slowly but change quickly           D. develop and change quickly

43. From the text we may know that Americans are ________.

A. kind               B. rude              C. sad               D. impolite

44. If you no longer work with an american, what should you do with your friendship?

A. Try your best to keep it.                    B. Avoid meeting your workmates.

C. Let it be.                                D. worry about it.