问题 选择题

有两种气态烃组成的混合气体完全燃烧后所得到的CO2和H2O的物质的量随混合烃的总物质的量的变化如右图所示,则下列对混合烃的判断正确的是   

    

①一定有乙烯;②一定有甲烷;③一定有丙烷;④一定无乙烷;⑤可能有乙烷

A.①②⑤

B.②⑤

C.②④

D.②③

答案

答案:C

题目分析:由图可知两种气态烃的平均组成为C1.6H4,根据碳原子平均数可知,混合气体一定含有CH4,由氢原子平均数可知,另一气态烃中氢原子数目为4,碳原子数目大于1.6,不超过4。

①两种气态烃的平均组成为C1.6H4,根据碳原子平均数可知,混合气体一定含有CH4,由氢原子平均数可知,另一气态烃中氢原子数目为4,可能含有C2H4,或含有C3H4等,若含有C2H4,满足甲烷与C2H4为2:3,故①错误;

②两种气态烃的平均组成为C1.6H4,根据碳原子平均数可知,混合气体一定含有CH4,故②正确;

③C3H8中氢原子数目为8,氢原子数目大于4,不可能含有C3H8,故③错误;

④C2H6中氢原子数目为6,氢原子数目大于4,不可能含有C2H6,故④正确;

⑤可能有C2H2中氢原子数目为2,氢原子数目小于4,不可能含有C2H2,故⑤错误;

故选C。

点评:本题考查烃混合物分子式确定,难度较大,注意利用平均分子组成判断烃的组成,常用方法有1、平均碳法 2、平均氢法 3、平均碳氢分子式法 4、平均式量法。

完形填空
.
Section C
Directions: Read the following passage and choose the most suitable heading from A-F for each paragraph.  There is one extra heading which you do not need.
(D)
A. Promise behaviors
B. Attitude beats experience
C. Job-winning qualities
D. Employer and employee relation
E. Stable career choices
F. Importance of teamwork skills
Despite the economy, experts advice students to major in what interests them.
 
76.
Aware of the worst job market in more than 25 years, many students enrolling in colleges and universities this fall are considering majors that they believe will land them stable career. 
Students with degrees in nursing, health care, accounting, computer, general science and engineering report the most success in finding jobs. Those with degrees in finance, journalism, graphic design, and international relations have had tougher times, liberal arts graduates also struggle.
 
77.
Still career experts say students should major in whatever area most interests them, even if it’s a less specialized liberal arts field, such as Chinese and or sociology. In a national survey, communication, followed closely by a strong work ethic and team work skills, was rated at the most important qualities sought by employers. “Liberal arts teaches us how to learn. When we go out into the world of work, we are going to have to continue to learn,” said Dan Naegeli, director of the university of North Texas career center.
 
78.
Texas Health Resources uses a wide range of workers at its 14 hospitals and other sites. The 18,000 employees company hires about 2000 people a year. It looks for candidates with “promise (有前途的) behaviors,” human resource director Justin Clem said.
“The resume is great… Education is wonderful,” Clem said. “But when we interview, we really want to look at situations they were put into the past, what actions they took, and what were the results. Do these results really support treating other people with courtesy dignity and respect? And communicating clearly and earning people’s trust? And thinking before they act?”
 
79.
The company also looks for people who have record of providing service, said Janaelle Nowne, vice president of human resource. If a student mowed lawns or worked at a fast-food restaurant, she said, “ the things that we would want to hear is how you attended to providing service to people that you were working with and how you were attending to the quality of the products that you have. ”
“Experience is always helpful, but it is not always the guarantee that person is going to get the job,” she added. “We look at the behaviors and the attitude they bring in and their willingness to be a part of the team.”
 
80. 
Lockheed Martin has all sorts of jobs in all sorts of fields. One of the skills recruiters consider is the ability to work in teams.
“Most of what we do is problem solving, and you get people with different kinds of skills together to solve the problem,” said Norman Robbins, senior manager community relations. “If you are real bright but you can’t get along with anybody, you’re not going to be as successful as you will be if you can work in teams.”
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