问题 填空题

在温度t1和t2下,X2(g)和H2反应生成HX的平衡常数如下表

⑴已知t2>t1,HX的生成反应是________反应(填“吸热”或“放热”)。

⑵HX的电子式是________。

⑶共价键的极性随共用电子对偏移程度的增大而增强,HX共价键的极性由强到弱的顺序是________。

⑷X2都能与H2反应生成HX,用原子结构解释原因:________________。

⑸K的变化体现出X2化学性质的递变性,用原子结构解释原因:________________,原子半径逐渐增大,得电子能力逐渐减弱。

⑹仅依据K的变化,可以推断出:随着卤素原子核电荷数的增加,________(选填字母)。

a. 在相同条件下,平衡时X2的转化率逐渐降低

b. X2与H2反应的剧烈程度逐渐减弱

c. HX的还原性逐渐减弱

d. HX的稳定性逐渐减弱

答案

⑴放热

⑶HF、HCl、HBr、HI

⑷卤素原子的最外层电子数均为7

⑸同一主族元素从上到下原子核外电子层数依次增多

⑹ad

阅读理解

The mystery stories of Sir Arthur Conan Doyle are famous all over the world.

The detective in his stories is called Sherlock Holmes. He solves mysteries in a most surprising way. His assistant, Dr Watson, watches with admiration and then writes up the story of the mystery afterwards.

This is a useful story writing skill. Because Watson is not very clever, the story remains a mystery until the end. The readers can sometimes pick up some clues before he does! Then, to make Watson understand the mystery, Holmes has to explain it all, step by step. So we, the readers, get to see it step by step too. Watson is almost as good a character in the story as Sherlock Holmes!

The very first time they meet, Holmes greatly surprises Watson. When they are first introduced, Holmes says to Watson, ‘How do you do? I see you have been to Afghanistan(阿富汗).’

Watson is too amazed by this to ask Holmes how he knows this. Watson has, indeed, been to Afghanistan. Later, he asks Holmes about it. Holmes explains that there is nothing magical about what he does. He gets to know it all by very, very careful observation(观察).

Observation One

Watson was introduced to Holmes as a doctor. Yet Holmes thought that the way he stood and walked made him seem like a soldier. So, this meant he was probably an army doctor.

Observation Two

Watson's face was quite dark skinned. But his wrists were pale. So his dark face was probably sun burnt. This meant that he had been to a hot, sunny country.

Observation Three

At the time, the British army had soldiers at bases in many parts of the world. So there were still a lot of places to choose from. However, Holmes saw that Watson looked very tired and he was always holding his left arm, as if it was painful. So, he had probably been with the army to a place where they were fighting. There was only one place where the British army was fighting at that time: Afghanistan.

小题1:The writer most probably created the character, Dr Watson, to ______.

A.give Holmes help when solving mysteries

B.show Holmes' careful observation

C.help readers pick up some clues about the mystery

D.get readers to see the mystery step by step小题2: The first time they meet, ______.

A.Holmes explains how he knows Watson has been to Afghanistan

B.Holmes surprises Watson by telling that he has been to Afghanistan

C.Watson tells Holmes he has been to Afghanistan

D.Watson asks Holmes how he knows he has been to Afghanistan小题3:From the passage we know that the British army ______ at that time.

A.only had soldiers in Afghanistan

B.had many army doctors at bases in many parts of the world

C.was fighting with several countries

D.was fighting with Afghanistan

单项选择题