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问题 选择题

下列各组离子，能在水溶液中大量共存的是（　　）

A．Na+   H+   Cl- HCO3-

B．K+ Na+  OH- AlO2-

C．K+ Ca2+  OH-  CO32-

D．Fe3+  OH- Br- NO3-

答案

A．因H+、HCO3-结合生成水和气体，则不能共存，故A错误；

B．因该组离子之间不反应，则能够共存，故B正确；

C．因Ca2+、CO32-能结合生成沉淀，则不能共存，故C错误；

D．因Fe3+、OH-结合生成沉淀，则不能共存，故D错误；

故选B．

阅读理解

根据短文内容，回答下列问题。

     My name is Sofia. I'm in Class 4, Grade 2. I'm in Row 3. Kate is my friend. She is in my class, too.

She is in Row 1. My father has a beautiful car. The number is B-047968. Her father has a beautiful car,

too. The number is E-0-double 4-double 9-5. Her father often drives her to my home. We are good

friends. We are both fifteen. 

1. Are Sofia and Kate both students?

A. No, they aren't.

B. No, they are.

C. Yes, they aren't.

D. Yes, they are.

2. What row is Sofia in?

A. She is in Row Four.

B. She is in Row Two.

C. She is in Row One.

D. She is in Row Three.

3. What's the number of Kate's father's car?

A. It's B-047968.

B. It's E-032143.

C. It's B-032146.

D. It's E-044995.

4. How old is Sofia?

A. She is fifteen.

B. She is thirteen.

C. She is fourteen.

D. She is twelve.

5. What's the number of Sofia's car? 

    It's ______.

A. It's B-047968.

B. It's E-032143.

C. It's B-032146.

D. It's E-044995.
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填空题

如图所示，A、B、C、D是匀强电场中一正方形的四个顶点，已知A、B、C三点的电势分别为ϕA=15V，ϕB =3V，ϕC =-3V，由此可知D点电势ϕD=______V；若该正方形的边长为2cm，且电场方向与正方形所在平面平行，则场强为E=________V/m。
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