题干

加热N2O5,依次发生分解反应:①N2O5(g)⇌N2O3(g)+O2(g)、②N2O3(g)⇌N2O(g)+O2(g).在体积为2L的恒容密闭容器中充入8mol N2O5,加热到T℃时O2和N2O3的物质的量分别为9mol、3.4mol,则T℃时
c
(
N
2
O
3
)
c
(
O
2
)
c
(
N
2
O
5
)
为(   )

A:10.7

B:8.5

C:9.6

D:10.2

上一题 下一题 0.0难度 选择题 更新时间:2010-07-15 12:52:42

答案(点此获取答案解析)

B

同类题1

阅读理解

    Recordings of angry bees are enough to send big, tough African elephants running away, a new study says. Beehives (蜂窝)—either recorded or real—may even prevent elephants from damaging farmer's crops.

    In 2002, scientist Lucy King and her team found that elephants avoid certain trees with bees living in them. Today, Lucy wants to see if African honeybees might discourage elephants from eating crops. But before she asked farmer to go to the trouble of setting up beehives on their farms, she needed to find out if the bees would scare elephants away.

    Lucy found a wild beehive inside a tree in northern Kenya and set up a recorder. Then she threw a stone into the beehive, which burst into life. Lucy and her assistant hid in their car until the angry bees had calmed down. Next,Lucy searched out elephant families in Samburu National Reserve in northern Kenya and put a speaker in a tree close to each family.

    From a distance, Lucy switched on the pre-recorded sound of angry bees while at the same time recording the elephants with a video camera. Half the elephant groups left the area within ten seconds. Out of a total of 17 groups, only one group ignored the sound of the angry bees. Lucy reported that all the young elephants immediately ran to their mothers to hide under them. When Lucy played the sound of a waterfall (瀑布) instead of the angry bees to many of the same elephant families, the animals were undisturbed. Even after four minutes, most of the groups stayed in one place.

    Lucy is now studying whether the elephants will continue to avoid the sound of angry bees after hearing it several times. She hasn't tested enough groups yet to know, but her initial (最初的) results were promising enough to begin trials with farmers. She has now begun placing speakers in the fields to see if elephants are frightened away.