问题 选择题

在一定温度下,可逆反应:A2(气)+B2(气)⇌2AB(气),达到平衡的标志是(  )

A.容器的总压强不随时间而变化

B.单位时间内有n molA2生成的同时有n molB2生成

C.单位时间内有n molB2发生反应的同时有n molAB分解

D.单位时间内生成n molA2同时就有2n molAB生成

答案

A.反应物与生成物气体的体积相等,无论是否达到平衡状态,容器的压强都不变,不能用压强作为判断达到平衡状态的标志,故A错误;

B.反应速率之比等于化学计量数之比,无论是否达到平衡状态,有n molA2生成的同时有n molB2生成,不能作为判断达到平衡状态的标志,故B错误;

C.单位时间内有nmolB2发生反应的同时有nmolAB分解,正逆反应速率不等,反应没有达到平衡,故C错误;

D.单位时间内生成nmolA2同时就有2nmolAB生成,正逆反应速率相等,反应达到平衡状态,故D正确.

故选D.

单项选择题
阅读理解

On Christmas Eve a few years ago an English couple received a very special telephone call. It was only a 20-second call but it was very important. The Haydens’ 15-year-old daughter had disappeared six months before. On Christmas Eve she rang them. “I’m phoning to wish a happy Christmas,” she said, “I love you.”

Ronals and Edwine Hayden were so happy that they started a special telephone service called “Alive and Well”. The service helps parents to get in touch with children who have run away from home.

Young people can phone “Alive and Well” and leave a message for their parents. The telephones are answered by answering machines. So no one can speak to the child of making him return home.

Parents of runaway children who are under eighteen can ask the police to bring their children home, so children do not want to tell their parents where they are. Through “Alive and Well” they can telephone their parents without worrying about this or giving out their addresses.

The Haydens and their helpers write down the tape recorded telephone messages and connect the address given. Many of the 30,000 British teenagers who have left home are probably in London. For only two pence they can go into a telephone coin box and call their parents. They can dial (拨) 5675339 and stop a parent’s worry: Is he dead or alive?

小题1:The Haydens’ daughter rang her parents         .

A.because she knew she had done something wrong

B.in order to give them her address

C.to say she was coming home soon

D.in order to comfort her worried parents小题2:If you ring “Alive and Well”,         .

A.you will get the information you want

B.your message will be passed over to your parents

C.the police will bring you home

D.your parents will know where you are小题3:From the passage, we can know that ________.

A.the Haydens received an “Alive and Well” call before Christmas

B.an “Alive and Well” call usually costs a lot

C.30,000 British teenagers enjoyed the “Alive and Well” service

D.an “Alive and Well” call is very important for worrying parents小题4:Through “Alive and Well”, parents of runaway children         .

A.often fail to persuade their children to return home

B.know nothing from their children

C.can say nothing to their children

D.can ask the police to help them to find lost children小题5:What can we know about the Haydens’ daughter from the passage?

A.She died six months ago.

B.She had a quarrel with her parents.

C.She worked in “Alive and Well”.

D.She ran away from home half a year ago.