问题 填空题

用化学用语表示下列物质或反应:

(1)氢氧化钙:______;

(2)镁条用砂纸打磨后放入氧气中,过一会儿,光亮的镁条变暗,反应的化学方程式是______;

(3)硝酸钡溶于水电离出的离子______;

(4)某硫的氧化物中硫元素的化合价为+6价,该氧化物是______.

答案

(1)氢氧化钙的化学式写法:金属元素在左边,氢氧根在右边,可以写出化学式Ca(OH)2

(2)镁条用砂纸打磨后放入氧气中,过一会儿,光亮的镁条变暗,镁与氧气发生氧化反应:2Mg+O2═2MgO

(3)硝酸钡溶于水电离出的离子Ba2+,NO3-,所以电离方程式为:Ba(NO32═Ba2++2NO3-

(4)设硫的氧化物的化学式为:SXOY,已知硫元素的化合价为+6价,氧元素的化合价为-2价,所以(+6X)+(-2Y)=0即

X
Y
=
1
3

所以硫的氧化物的化学式为S1O3,1省略不写,则硫的氧化物的化学式为SO3.

故答为:(1)Ca(OH)2

(2)2Mg+O2═2MgO

(3)Ba(NO32═Ba2++2NO3-

(4)SO3

填空题



Having been a student and teacher in China (at Peking and Tsinghua Universities,
respectively), I know quite a few Chinese students. Indeed,
(1)______ all of them have gone (1)______
to the United States to (2)______ their studies. (2)______
Like the larger body of Chinese students in the United States---totaling well over 40,000--my friends live across the
vast expanse of the American continent, on both coasts and in the states in between. They have chosen fields of study
ranging from environmental engineering and public policy to history and Asian studies. Yet despite the great diversity
among these students in terms of their ages, backgrounds, locations,
and majors, (3)______ experiences remain. (3)______
None are more pronounced that the inability of most Chinese students to effectively immerse themselves in American
society. It seems to me that the majority of Chinese students in the United States have never made the effort to reach out
and embrace American life on its own terms, instead, most share apartments with one or more fellow Chinese students,
speaking Chinese and eating Chinese food on a daily basis. In some respects, it is as if these students had never left China.
Interactions with Americans tend to be limited to relatively formal, academic settings, such as the classroom or a professor’s
office. Moreover, few Chinese students participate in campus-wide (4)______ activities, (4)______
such as athletic matches and dances, which would put them into contact with a diverse array of American young
people. Rather, most limit themselves to taking part in programs arranged by the Chinese Students Association and,
naturally, these events are generally linked to uniquely Chinese occasions such as the Spring Festival and National Day. As
a result, even Chinese students who have spent years in the United States often difficult to engage American friends in
(5)______ conversations about(5)______
such subjects as American politics, race relations, and popular music.
In short, they lack a "feel" for the country. Chinese students widely acknowledge this phenomenon even as they
maintain differing views as to its cause.
Some contend that Chinese have difficulty (6)______ the cultural divide on account of such practical considerations as
money. (6)______
Because Chinese students come from a developing country and often have to rely on limited scholarship funds for
support, they argue, Chinese students simply do not have the financial means to more fully participate in the extra-
curricular and social activities
which would afford them more (7)______ contact with American (and other foreign) students.(7)______
The truth is, however, that most American students are just as poor; it is a common fact of
American student life.
And in any event, most campus-based social events are (8)______ to meet student needs.(8)______
Others believe that the reason Chinese find acculturation difficult is somewhat more complex. Fundamentally, few
Chinese see the chance to study in the United States for what it is: a once in lifetime opportunity to get to know another
country from the inside. Chinese students typically focus so single-mindedly on their studies that they lose sight of the
larger picture, that is, their ultimate role as cultural interpreters between their homeland and the United States. To be sure,
a Chinese student’s service as an engineer or biologist is
(9)______ to China’s continued economic construction, (9)______
but his or her ability to bridge the divide---or often, the perceived divide-between two distinct cultures is perhaps even
more important over the long run. Today, only a small fraction of the Chinese students who have studied in the United States
have returned to China, a proof of both the academic and professional success of Chinese students in the United States and the
openness of the society in which they found this success. The contributions Chinese students have made to American life are
truly striking. Still, I believe that the next generation of Chinese students in the United States---those who will begin the 21st
century there-will recognize their crucial function in the process of furthering U. S. ---China understanding.
They will return to China in (10)______ numbers to contribute to their country’s (10)______
development in unprecedented ways. I only hope that before these students find their way back to China, they find their way into the heart of America.

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