题目

Twenty years ago, I drove a taxi for a living. One night I went to pick up a passenger at 2:30 a. m. When I arrived to collect, I found the building was dark except for a single light in a ground floor window.I walked to the door and knocked, Just a minute, answered a weak, elderly voice.After a long time, the door opened. A small woman in her eighties stood before me. By her side was a small suitcase.I took the suitcase to the car, and then returned to help the woman. She took my arm and we walked slowly towards the car.She kept thanking me for my kindness. It's nothing, I told her. I just tr将等物质的量的A、B混合于2 L的密闭容器中，发生如下反应：3A（g）＋B（g）xC（g）＋2D（g），经5 min后，测得D的浓度为0.5 mol/L，c（A）∶c（B）＝3∶5，C的平均反应速率为0.1 mol/（L·min）。求：（1）此时A的浓度c（A）＝________mol/L，反应开始前容器中的A、B的物质的量：n（A）＝n（B）＝________mol；（2）B的平均反应速率v（B）＝________mol/（L·min）；（3）x的值为________。