问题 选择题

在一密闭容器中,有甲、乙、丙、丁四种物质,在一定条件下存在某个反应,测得反应前后各物质的质量如下表:

物质
反应前质量/g20m2020
反应后质量/g2待测3226
对该反应,下列描述正确的是(  )

A.该反应中甲、丙、丁的质量比为1:16:13

B.乙在该反应中一定是催化剂

C.待测质量一定为4g

D.该反应是分解反应

答案

A、根据各物质反应前后质量的变化可知甲为反应物,丙、丁为生成物.故该反应为:甲、丙、丁的质量比为18g:12g:6g=3:2:1.,所以A不正确.

B、该反应参加的甲的质量为18g,生成的为丙的质量为12g、丁的质量为6g,故乙的质量反应前后不变,故可能是催化剂,也可能没有参加.故B答案不正确.

C、乙的质量反应前后不变,但由于反应前乙的质量未知,故待测质量不一定为4g.

D、由于乙的质量反应前后不变,所以该反应的反应物为甲,生成物为丙和丁,故该反应为分解反应.所以D正确.

故选D.

阅读理解

阅读短文,选择正确答案。

    The Great Fire of London started in the very early hours of 2 September, 1666. In four days it destroyed

more than three-quarters of the old city, where most of the houses were wooden and close together. One

hundred thousand people became homeless, but only a few lost their lives.  

    The fire started on Sunday morning in the house of the King's baker (面包师) in Pudding Lane. The baker,

with his wife and family, was able to get out through a window in the roof. A strong wind blew the fire from

the bakery (面包房) into a small hotel next door. Then it spread quickly into Thames Street. That was the

beginning.

    By eight o'clock three hundred houses were on fire. On Monday nearly a kilometer of the city was burning

along the River Thames. Tuesday was the worst day. The fire destroyed many well-known buildings, old

St Paul's and the Guildhall among them.  

    Samuel Pepys, the famous writer, wrote about the fire. People threw their things into the river. Many poor

people stayed in their houses until the last moment. Birds fell out of the air because of the heat.  

    The fire stopped only when the King finally ordered people to destroy hundreds of buildings in the path of the

fire. With nothing left to burn, the fire became weak and finally died out.  

    After the fire, Christopher Wren, the architect (建筑师), wanted a city with wider streets and fine new

houses of stone. In fact, the streets are still narrow; but he did build more than fifty churches, among them new

St Paul's.  

    The fire caused great pain and loss, but after it London was a better place: a city for the future and not just of

the past.

1. The underlined word "family" in the second paragraph means _______. [ ]

A. home         

B. children  

C. wife and husband   

D. wife and children

2. How was the fire put out according to the text? [ ]

A. The king and his soldiers came to help.  

B. All the wooden houses in the city were destroyed.  

C. People managed to get enough water from the river.  

D. Houses standing in the direction of the fire were pulled down.

3. It seems that the writer of the text was most sorry for the fact that _______. [ ]

A. some people lost their lives  

B. the birds in the sky were killed by the fire  

C. many famous buildings were destroyed  

D. the King's bakery was burned down

4. Why did the writer cite (引用) Samuel Pepys? [ ]

A. Because Pepys was among those putting out the fire.  

B. Because Pepys also wrote about the fire.  

C. To show that poor people suffered most.  

D. To give the reader a clearer picture of the fire.

5. Which of the following were reasons for the rapid spread of the big fire?

(a) There was a strong wind.  

(b) The streets were very narrow.

(c) Many houses were made of wood.  

(d) There was not enough water in the city.  

(e) People did not discover the fire earlier. [ ]

A. (a) and (b)

B. (a), (b) and (c)  

C. (a), (b), (c) and (d)

D. (a), (b), (c), (d) and (e)

填空题