问题 单项选择题

利用( )才能控制种群密度过快增长。

A.正反馈
B.负反馈
C.多元重复控制
D.多层次控制

答案

参考答案:B

解析: 负反馈是指一种生物增长引起另一种生物减少,这种内部调节能够控制种群过快增长,故选B。

填空题

(10分)(1) 氨是氮循环中的重要物质,氨的合成是目前普遍使用的人工固氮方法。

(1)已知:H-H键能为436KJ·mol-1,N≡N键能为945 KJ·mol-1,N-H键能为391 KJ·mol-1。写出合成氨反应的热化学方程式:                               

(2)可逆反应N2 +3H22NH3 在恒容密闭容器中进行,达到平衡状态的标志是   

①单位时问内生成n mo1 N2的同时生成3n mol H2

②单位时间内1个N≡N键断裂的同时,有6个N—H键断裂

③容器中N2、H2、NH3的物质的量为1:3:2

④常温下,混合气体的密度不再改变的状态

⑤常温下,混合气体的平均相对分子质量不再改变的状态

(3)恒温下,往一个2L的密闭容器中充入2.6 mol H2和1 mol N2,反应过程中对NH3的浓度进行检测,得到的数据如下表所:

时间/min51015202530
C(NH3)/mol·L-10.080.140.180.200.200.20
     5min内,消耗N2的平均反应速率为     ;此条件下该反应的化学平衡常数K=        ;反应达到平衡后,若往平衡体系中加入H2、N2和NH3各2mol,化学平衡将向         (填“正反应”或“逆反应”)方向移动。

(4)氨是氮肥工业的重要原料。某化肥厂以天然石膏矿(主要成分CaSO4)为原料生产铵态氮肥(NH4)2SO4,(已知Ksp(CaSO4)=7.10×10-5 Ksp(CaCO3)=4.96×10-9)其工艺流程如下:

请写出制备(NH4)2SO4的反应方程式:                                 

并利用有关数据简述上述反应能发生的原因                                            

单项选择题

Generally speaking, a British is widely regarded as a quiet, shy and conservative person who is (1) only among those with whom he is acquainted. When a stranger is at present, he often seems nervous, (2) embarrassed. You have to take a commuter train any morning or evening to (3) the truth of this. Serious-looking businessmen and women sit reading their newspapers or dozing in a corner; hardly anybody talks, since to do so would be considered quite offensive. (4) , there is an unwritten but clearly understood code of behavior which, (5) broken, makes the offender immediately the object of (6) .

It has been known as a fact that a British has a (7) for the discussion of their weather and that, if given a chance, he will talk about it (8) . Some people argue that it is because the British weather seldom (9) forecast and hence becomes a source of interest and (10) to everyone. This may be so. (11) a British cannot have much (12) in the weathermen, who, after promising fine, sunny weather for the following day, are often proved wrong (13) a cloud over the Atlantic brings rainy weather to all districts! The man in the street seems to be as accurate — or as inaccurate — as the weathermen in his (14) .

Foreigners may be surprised at the number of references (15) weather that the British make to each other in the course of a single day. Very often conversational greetings are (16) by comments on the weather. "Nice day, isn’t it" "Beautiful!" may well be heard instead of "Good morning, how are you" (17) the foreigner may consider this exaggerated and comic, it is worthwhile pointing out that it could be used to his advantage. (18) he wants to start a conversation with a British but is (19) to know where to begin, he could do well to mention the state of the weather. It is a safe subject which will (20) an answer from even the most reserved of the British.

7()

A.emotion

B.fancy

C.likeness

D.judgment