搜题请搜索小程序“爱下问搜题”
问题 选择题

2011年5月1日，我国将惩治“酒驾”写入刑法并正式实施，交警使用的酒精检测仪中含一种对酒精非常敏感的物质K2Cr2O7，该化合物中铬元素（Cr）的化合物为（　　）

A．+6

B．+5

C．+4

D．+3

答案

在K2Cr2O7中，钾元素的化合价为+1价，氧元素的化合价为-2价，

设重铬酸钾中Cr元素的化合价为x，

由化合物中各元素的正负化合价的代数和为0，则（+1）×2+x×2+（-2）×7=0

解得x=+6；

故选A．

翻译题

阅读下面短文，将文中划线部分译成汉语或英语。

    Food is very important. Everyone needs to eat well if he or she wants to have a strong body. 1 Our minds

also need a kind of food. This kind of food is knowledge. We begin to get knowledge even we are very young.

2 孩子们对周围的一切都感兴趣.They learn something when they are watching and listening. When they are

getting older, they begin to read storybooks, science books and anything they like. 3 When they find something

new, they love to ask questions and try to find out the answers.

   4 获取知识的最佳方法是什么呢? If we learn by ourselves, we will get the most knowledge. If we are

always getting answers from others and do not ask why, we will never learn well. 5 If we study in the right

way, we will learn more and understand better.

1                                                                                              

2                                                                                              

3                                                                                              

4                                                                                              

5                                                                                              

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单项选择题

RT型温度继电器不调主弹簧，只调节幅差螺帽改变空动间隙，将改变（）。

A.温度上限

B.温度下限

C.A~B

D.A和B
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