在一定温度下，向恒容密闭容器中加入2mol X气体和4 mol Y 气_爱下问搜题

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问题选择题

在一定温度下，向恒容密闭容器中加入2mol X气体和4 mol Y 气体，发生如下反应：X（s）+2Y（g） 2Z（g），此反应达到平衡的标志是（）

A．容器内压强不随时间变化

B．V_正（_X_）＝2V_逆（_Z_）

C．容器内X、Y、Z的浓度相等

D．容器内气体密度不变

答案

答案：D

因为反应前后气体的体积不变，所以其压强始终不变，A不可以。因为X是固体，不能用来表示反应速率，B不正确。容器内X、Y、Z的浓度相等，但不能说明正逆反应速率是否相等，C不能说明。密度是容器内气体的质量和容器体积的比值，容器体积不变，但气体的质量是变化的，所以当容器内气体密度不变时，是可以说明的。答案选D。

完形填空

After the quake hit northeast Japan on March 11, many moving stories that I saw with my own eyes happened around me.
I had to walk home since all the 41 had stopped after the earthquake. On my way home I 42 an old lady at a bakery shop who was giving out free bread, which made my heart 43 . A man was holding a sign that said, “Please use our 44 .” He was 45 his house for people to go to the restroom.
My friend wanted to 46 others. He stood in the cold with a sign “If you’re okay with a motorcycle, I will 47 you to your house.” And then I saw him take one gentleman home, all the way to a faraway place!
Then next day I drove to 48 my car with gas. There is a lack (缺乏) of 49 now and many gas stations are either closed or have very 50 lines. I got 51 , since I was behind 15 cars. Finally, when it was my 52 , the man smiled and said, “ 53 this situation, we are only giving $30 worth gas per person. Is that alright?” “ 54 . I’m just glad that we are all able to 55 ,” I said. His smile gave me so much comfort.
I saw a man at the evacuation (疏散) center 56 when people brought food to him. It was the first time in three days that food was brought to their center. However, after he wiped the tears, his next 57 surprised me. “I am very 58 that we are provided with food. But people in the city next to us haven’t 59 any food at all. Please go to that center as well.” And when hearing that, I realized there is a bright future on the other side of this 60 .

A．information

B．Together with

单项选择题 A1型题

下列关于口腔颌面部感染错误的是（）

A.口腔颌面部血运丰富，有利于炎症的吸收和愈合

B.口腔颌面部血运丰富，感染易向颅内扩散引起严重并发症

C.口腔颌面部有众多的潜在筋膜间隙，是控制感染发展的有效屏障

D.口腔颌面部有多数体腔与外界相通，其表面的常驻菌是感染的易发因素

E.口腔颌面部感染最常见的原因是牙源性感染