问题 选择题

已知反应mX(g)+nY(g)⇌qZ(g),△H<0,m+n>q,在恒容密闭容器中反应达到平衡时,下列有关说法正确的是(  )

A.如果继续通入一定量某气体使体系压强增大,平衡将正向移动

B.此时,X的正反应速率是Y的逆反应速率的

m
n

C.如果降低温度,且保持物质状态不发生改变,混合气体的平均相对分子质量变小

D.如果增加X的物质的量,平衡正向移动,X的转化率增大

答案

A、恒容条件下,通入稀有气体使压强增大,反应混合物的浓度不变,正、逆反应速率不变,平衡不移动,故A错误;

B、可逆反应达平衡时不同物质表示的正、逆反应速率之比等于化学计量数之比,X的正反应速率是Y的逆反应速率的

m
n
倍,说明反应到达平衡,故B正确;

C、降低温度平衡向正反应移动,由于m+n>q,反应混合气体总的物质的量减小,混合气体总质量不变,结合M=

m
n
可知混合气体的平均摩尔质量增大,故降低温度,混合气体的平均相对分子质量增大,故C错误;

D、增加X的物质的量,X的浓度增大,平衡正向移动,X的转化率降低,故D错误.

故选B.

完形填空

Directions: Read the following passage. Complete the diagram by using the information for the passage. Write NO MORE THAN 3 WORDS for each answer.

Aids today

Aids, the short form for acquired immune deficiency syndrome, is caused by a virus called HIV, which enters a person’s blood and attacks the body’s immune (免疫的) system. There is no cure for HIV or Aids, and after a person has been infected, he or she will always carry the virus. Sometimes, infected people have no outward symptoms.

HIV and Aids are spreading across the world at a frightening rate, with about 14,000 people being infected daily. The virus is spread in three ways -- through unprotected sex, blood-blood contact and mother-to-child transmission. Unprotected sex is the most common way that the virus is spread, accounting for 75 percent of adult infections worldwide.

Although many people are familiar with Aids and how it is transmitted, more than a few people hold the view that HIV and Aids are an African problem because the infection rates there are very high. However, HIV and Aids are a problem all over the world. Since the disease was discovered in the 1980s, it has become a serious problem in many places, infecting over 60 million people worldwide. According to the World Health Organization estimates from 2005, more than 4 million children had died from Aids, and more than 14 million children had lost their parents to Aids. All of this makes it clear that something must be done to stop this deadly disease.

The government is working hard to control the Aids epidemic and has opened labs to test and monitor the disease. In 2003, the government also started providing free drugs for Aids patients in need.

The United Nations has been very involved in fighting HIV and Aids around the world for many years now. UNAIDS, an organization founded in 1996, helps prevent the spread of Aids. The work includes providing infected people with help from doctors and testing for people. The organization also offers programs that teach Aids prevention to young people and sets up treatment centers.

填空题