4. 已知甲乙两种化合物都只含X、Y 两种元素，在甲中X元素的质量分数大于乙中的X元素的质量分数，若甲的化学式为XY₂，则乙的化学式可能为　　　　　　　　 (　　　 )

A．XY　　　　　 B．X₂Y₅　　　　　 C．X₂Y₃　　　　　 D．X₂Y

为偶数的有　　　　

　　 A．2种　　　　 B．3种　　　　 C．4种　　　　 D．8种

3.将aL NH₃通过灼热的装有铁触媒的硬质玻璃管后，气体体积变为bL(气体体积均在同温同压下测定)，该bL气体中NH₃的体积分数是　　　　　　　　　　　　

A. 　　　　B. 　　　　C. 　　　　D.

2．有关键能数据如表：

晶体硅在氧气中燃烧的热化学方程式：Si(s)+O₂(g)==SiO₂(s)中,△H= -989.2 kJ·mol^-1，则X的值为

A. 423.3　　　　　 B. 920　　　　　　 C. 1165.2　　　　　　　 D. 460

1．下列除杂质和分离提纯的实验操作中，错误的是

A．除去蛋白质溶液中混有的少量食盐：渗析

B．除去CO₂中混有的少量SO_2，将气体通过盛有足量Na₂CO₃溶液的洗气瓶

C．除去乙醇中混有的少量水：在乙醇中加入新制的生石灰，加热蒸馏　

D．除去乙酸乙酯中混有的少量乙醇，加入饱和碳酸钠溶液振荡静置分层后分液

第二节：书面表达(满分25分)

假如你是高三的学生，最近你就高三模拟考试该偏难还是该偏易这个问题进行了一次调查。请结合下表内容，用英语写一篇短文，介绍有关调查情况，并发表自己的看法。

注意：1．词数120左右。2．可适当增加细节，以使行文连贯。

one possible version：

Recently I have made an investigation on whether a model-test paper for Senior Three should be difficult or easy．Opinions are divided on this matter．

Some students think that a difficult exam is just like a challenge．The harder, the better．It can help students find out where they are weak in studies and improve their learning approaches.

Others，however，are against a difficult exam．In their opinion，if it is very difficult，they may become discouraged and feel terrible about the coming College Entrance Examination．Besides，with an easy exam，they can get high marks and gain confidence．

I prefer it to be neither too difficult nor too easy, because if it is too easy, teachers will not know how we are actually getting on with our studies, and if it is too difficult, we will lose heart.

第一节：对话填空(共10小题：每小题1分，满分10分)

W: Do you have 76 o_______ pastimes(业余爱好) besides stamp collecting?

M：Yes, fishing．

W：That’s very 77 p_______, too．Every time I pass the lake，I see many people sitting there with a rod in hand，but I’ve never seen anyone catch anything．

M：78 M______ it’s because you lack the patience．

W：I would break my rod if I sat about for 79 h_______ getting nothing．

M：Oh，look at that man’s pole．It's bent 80 l_______ a bow．There must be a huge fish on the end of the line．Let’s go over and 　81 h______ a look．

W：OK．Wow，what a big fish!

M．So it is 82 i______ to fish with a rod sitting at the lake．Say what do you often do in your 83 s_______ time?

W：Oh, 84 n________ special．I read，watch TV and go to movies.

M：Don't you have any hobbies，like stamp collecting or 85 t________ like that?

W：No，I don’t have any hobbies．