问题 问答题

发射通讯卫星的火箭用联氨(N2H4)做燃料,用四氧二氮(N2O4)助燃,生成物不会对大气造成污染.

(1)反应的化学方程式为:2N2H4+N2O4=3______+4H2O,请在横线上填写化学式以完成该化学方程式.

(2)请计算9.6kgN2H4完全燃烧需要助燃物N2O4的质量.

答案

(1)反应前反应物中N、H、O元素的原子个数依次为:6、8、4,反应后生成物中H、O原子个数为8、4;比较反应前后原子种类及个数可得知,3个未知物的分子中应含有6个N原子,所以,未知物的化学式为N2

故答案为:N2(1分);

(2)设需要助燃物N2O4的质量为x

2N2H4+N2O4=3N2+4H2O

64    92(1分)

9.6kg  x(1分)

64
9.6kg
=
92
x
(1分)

x=13.8kg(1分)

答:需要助燃物N2O4的质量为13.8kg.(1分)

阅读理解

Started in 1636, Harvard University is the oldest of all the colleges and universities in the United States. Yale, Princeton, Columbia and Dartmouth were opened soon after Harvard.

In the early years, these schools were nearly the same. Only young men went to college. All the students studied the same subjects, and everyone learned Latin and Greek. Little was known about science. And few people knew that one kind of school could teach everything that was known about the world. When the students graduated, most of them became ministers or teachers.

In 1782, Harvard started a medical school for young men who wanted to become doctors. Later, lawyers could study in Harvard's law school. In 1825, besides Latin and Greek, Harvard began to teach modern languages, such as French and German. Soon it began to teach American history.

As knowledge increased, Harvard and other colleges began to teach many new subjects. Students were allowed to choose the subjects that interested them. Today, there are many different kinds of colleges and universities. Most of them are made up of smaller schools that deal with special fields of learning. There's so much to learn that one kind of school can't offer all.

小题1:In the early years, people learned_______ in colleges.

A.science

B.medicine

C.law

D.Latin and Greek小题2:Most of college graduates became_______ in the early years.

A.lawyers

B.doctors

C.ministers or teachers

D.businessmen小题3:Which of the following is TRUE according to passage?

A.In the early years, everyone can go to colleges.

B.In 1782, Harvard began to teach German.

C.More and more courses were taught in college with the improvement of knowledge.

D.In the early years, different colleges majored in different fields.小题4:Nowadays college students_______.

A.can learn everything they are interested in

B.learn the same subjects

C.must learn Latin and Greek

D.go to different smaller schools

单项选择题