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问题 选择题

今有一混合物的水溶液，只可能含有以下离子中的若干种：Na+、NH、Ba2+、Cl－、CO、SO。现取两份200mL溶液进行如下实验：①第一份加足量NaOH溶液，加热，收集到气体1.36g；②第二份加足量BaCl2溶液后，得干燥沉淀12.54g，经足量盐酸洗涤、干燥后，沉淀质量为4.66g。根据上述实验，以下推测正确的是

A．一定不存在Ba2+，NH可能存在

B．CO一定不存在

C．Na+一定存在

D．一定不存在Cl－

答案

答案：C

根据实验①可知，溶液中一定含有NH4＋。氨气是1.36g，物质的量是0.08mol，则NH4＋也是0.08mol；根据实验②可知，硫酸钡的质量是4.66g，碳酸钡的质量是12.54g－4.66g＝7.88g，物质的量分别是0.02mol和0.04mol，则溶液中SO42－和CO32－的物质的量分别是0.02mol和0.04mol。所以溶液中一定没有Ba2＋。根据溶液的电中性可知，溶液中一定还含有钠离子，但氯离子是不能确定的，选项C正确，答案选C。

阅读理解
On the first day of class, Roni’s foreign students fill out form and give information about themselves.
Name: Claude Ansari                           Country: France
Native Language: Arabic                       Time in U.S.: 10 months
Please tell me a little about yourself.
Family: I live with my wife and 2-year-old daughter.
Work: I was an art school student in France. But now, I’m working as a cook.
Interests: I love to cook (and eat). I also like to go mountain climbing.
 
Name: Su Chen Wang                           Country: Taiwan, China
Native Language: Chinese                        Time in U.S.: 4 years
Please tell me a little about yourself.
Family: I have 3 boys and 2 girls. They’re all attending school here.
My husband is a businessman and lives in Taiwan.
Work: I was a maths teacher but now I’m a housewife.
Interests: I like indoor activities: reading, drawing, listening to music.
 
Name: Rorma Ruiz                          Country: Guatemala
Native Language: Spanish                     Time in U.S.: 2 years
Please tell me a little about yourself.
Family: My family—my mother and 4 brothers—lives in Guatemala. I’m here by myself.
Work: I worked as a nurse in my country. Here I’m a tailor.
Interests: I like to go to movies and buy videos. I love to study.
小题1:Who has lived in America for the shortest time?
A. Claude Ansari  B. Norma’s mother.   C. Su Chen Wang
小题2:__________worked in a hospital a few years ago.
A. Claude Ansari   B. Su Chen Wang      C. Norma Ruiz
小题3:Su Chen Wang’s children are attending school in ___________.
A. France         B. the U.S.          C. Taiwan
小题4:These three people will ___________ together.
A. go mountain climbing   B.listen to music    C. study in the same class
小题5:Which of the following is Not True?
A. They all had jobs before they came to America?
B. They all have children.
C. They are foreign students of a school in America now.
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问答题

如图是小型交流发电机的示意图，两磁极N、S间的磁场可视为水平方向的匀强磁场，为交流电流表．线圈绕垂直于磁场方向的水平轴OO′沿逆时针方向匀速转动，从图示位置开始计时，已知磁感应强度大小为B，线圈的匝数为n，线圈转动的角速度为ω，正方形线圈的边长为L，线圈的内阻为r，外电阻为R，则线圈产生的感应电动势e的表达式为：______；线圈从开始转过30°过程中，通过电阻R的电量为：______；线圈从开始转过90°过程中，外力对线圈所做的功为：______．
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