问题 选择题

常温下硫单质主要以S8形式存在,加热时S8会转化为S6、S4、S2等,当蒸气温度达到750°C时主要以S2形式存在,下列说法正确的是(  )

A.S8转化为S6、S4、S2属于物理变化

B.不论哪种硫分子,完全燃烧时都生成SO2

C.常温条件下单质硫为原子晶体

D.把硫单质在空气中加热到750°C即得S2

答案

答案:B

S8、S6、S4、S2属于不同的分子,它们之间的转化为化学变化;常温条件下单质硫为分子晶体;硫单质在空气中加热到750°C时被氧化,生成硫的氧化物,得不到S2

单项选择题
阅读理解

阅读理解。

     At a certain time in our lives we consider every place as the possible sites (地点) for a house. I have thus

searched the country within a dozen miles of where I live. In imagination I have bought all the farms, one

after another, and I knew their prices.

     The nearest thing that I came to actual ownership was when I bought the Hollowell place. But before

the owner completed the sale with me, his wife changed her mind and wished to keep it, and he offered me

additional dollars to return the farm to him. However, I let him keep the additional dollars and sold him the

farm for just what I gave for it.

     The real attractions of the Hollowell farm to me were its position, being about two miles from the village,

half a mile from the nearest neighbor, bounded (相邻) on one side by the river, and separated from the

highway by a wide field. The poor condition of the house and fences showed that it hadn't been used for

some time. I remembered from my earliest trip up the river that the house used to be hidden behind a forest

area, and I was in a hurry to buy it before the owner finished getting out some rocks, cutting down the apples

trees, and clearing away some young trees which had grown up in the fields. I wanted to buy it before he

made any more of his improvements. But it turned out as I have said.

     I was not really troubled by the loss. I had always had a garden, but I don't think I was ready for a large

farm. I believe that as long as possible it is better to live free and uncommitted (无牵挂的). It makes but little

difference whether you own a farm or not.

1. What do we know about the author? [ ]

A. He wanted to buy the oldest farm near where he lived.

B. He made a study of many farms before buying.

C. He made money by buying and selling farms.

D. He had the money to buy the best farm in the country.

2. Why did the author decide to buy the Hollowell place? [ ]

A. It was of good market value.

B. It was next to the highway.

C. It was in a good position.

D. It was behind a nice garden.

3. Why did the author want to buy the farm in a hurry? [ ]

A. He was afraid the owner might change his mind.

B. He hoped to enlarge the forest on the farm.

C. He wanted to keep the farm as it was.

D. He was eager to become a farm owner.

4. The underlined words "the loss" in the last paragraph refer to _____. [ ]

A. the money the author lost in buying the farm

B. the sale of the garden in the Hollowell place

C. the removal of the trees around the house

D. the failure to possess the Hollowell place

5. What does the author believe as important in life? [ ]

A. To own a farm

B. To satisfy his needs

C. To be free from worries

D. To live in the countryside