问题 选择题

下列图像中能表示过氧化氢和二氧化锰制氧气时,二氧化锰在反应混合物中的含量(a%)随时间(T)变化的曲线图是(t时表示反应已完全) (   )

答案

答案:A

题目分析:催化剂是一种物质,在化学反应里能改变其他物质的化学反应速率,而本身的质量和化学性质在反应前后都没有发生变化.因为二氧化锰属于催化剂,在反应前后质量不变,但氯酸钾的质量在不断的减少(由于氯酸钾在加热时不断产生氧气),所以二氧化锰的质量分数在不断增加,反应结束后就不变了,在没有反应时二氧化锰的质量分数不能是零.

故选A.

单项选择题 A1/A2型题
阅读理解

阅读理解。

     Ben and his wife Susan were on their way to have dinner with their friends. It was a dark,windy night, and

they did not know the way very well. They drove through a town until they found what they thought was the

road to Dorling, where their friends lived. But it soon became clear that they were not on the road to Dorling at

all. The road that they were on was getting narrower, and there were no other cars on it. The wind was blowing

harder with every minute that passed.

     They came to a small village. They drove past a church and then two houses without lights on. There was

nobody about to tell them where they were, or where the road went. Just then, Ben saw a telephone box twenty

meters or so further on. While he walked back along the road to see if there was a name outside the church,

Susan telephoned their friends and told them that they were still on their way.

     Their friends were just saying that the dinner was already getting rather cold, when Ben came back to the

telephone box, his head down against the wind. He said that there was a tree lying across the road, and that the

telephone lines were down. Susan heard nothing more from their friends about the dinner.

1. Some time later Ben and Susan found they took a wrong road because _____.  [ ]

A. their friends lived nearer than they drove

B. the road was getting narrower and their car alone was on it

C. the hard wind made them get lost

D. the road was not the same as before

2. Ben went to the church to see if there was a name outside because _____. [ ]

A. he was sure to find some people who knew Dorling

B. he hoped to get help from there

C. he wanted to telephone his friends where they were

D. he wanted to stay there for the night

3. Susan could hear nothing more from their friends because _____. [     ]

A. the telephone lines were broken by a tree

B. the strong wind made too much noise

C. they got angry

D. they had all left

4. From the passage we know _____.[ ]

A. Ben and his wife often went out for dinners

B. Ben and his wife lived in the country

C. Both Ben and his wife were shortsighted (近视的)

D. Ben and his wife seldom (很少) went to Dorling

5. Which of the following can be the best title for the passage?[ ]

A. Ben and His Wife

B. A Windy Night

C. The Cold Dinner

D. Where Is Dorling