问题 填空题

通常人们把拆开1 mol某化学键所吸收的能量看成该化学键的键能。键能的大小可以衡量化学键的强弱,也可用于估算化学反应的反应热(ΔH),化学反应的反应热等于反应中断裂旧化学键的键能之和与反应中形成新化学键的键能之和的差。

化学键Si-OSi-ClH-HH-ClSi-SiSi-C
键能/kJ·mol1460360436431176347
请回答下列问题:

(1)已知Si、SiC、SiO2熔化时必须断裂所含化学键,比较下列两组物质的熔点高低(填“>”或“<”):SiC_____Si,Si _____SiO2

(2)工业上高纯硅可通过下列反应制取:,则2 mol H2生成高纯硅需_____ (填“吸收”或“放出”)能量_____ kJ。

(3)已知硅燃烧热的热化学方程式为Si(s)+O2(g)===SiO2(s) ΔH=-989.2kJ·mol1,则O=O键键能为_____________。

答案

(1)>  <  (2)吸收  236    (3)498.8 kJ·mol1

(1)化学键越强,分子越稳定,所以碳化硅的稳定性强于硅。单质硅的稳定性弱于二氧化硅的。

(2)反应热就是断键吸收的能量和形成化学键所放出的能量的差值,所以该反应的反应热是360 kJ·mol1×4+2×436 kJ·mol1-4×431 kJ·mol1-176 kJ·mol1×2=236kJ·mol1,所以是吸热反应.

(3)设O=O键键能为x,由键能可知176 kJ·mol1×2+x-4×460 kJ·mol1=-989.2kJ·mol1,所以x=498.8 kJ·mol1.

问答题 简答题
阅读理解

阅读下面短文并回答问题

[1]Stamp collectors usually collect stamps only from certain countries or regions. The traditional method of stamp collecting is to organize stamp collection according to the issue dates.

[2]Of course, there are many ____________. You can collect stamps relating to a particular theme. For example, sport lovers may choose the Olympic theme. They try their best to find Olympic stamps issued by various parts of the world every four years. Some of them may want to concentrate on even more specific sport activities like ball games, gymnasium, swimming, etc.

[3]If you like astronomy, you may be keen on collecting stamps describing the stars, planets, spacecraft, spacemen, etc. once you have fixed the topic, you no longer need to bother about stamps other than the theme you selected. Then, you can put all your effort to collect the stamps around it.

[4]China issues zodiac animal stamps (十二生肖邮票) every year to celebrate the Lunar New Year. They are extremely popular and a lot of collectors wait patiently for 12 years to collect a full set of them. Hong Kong’s Lunar New Year special stamp series began in 2000 with the Year of Dragon and the twelfth and final set was issued in 2011, the Year of Rabbit. Recently some Western countries have issued zodiac animal stamps, which attract a lot of attention as well.

[5]You may choose any theme you like. However, you should bear in mind an essential point. The topic you choose should not be too narrow. Otherwise, it is very difficult to accumulate stamps around the topic. You will be depressed and even lose your interest in collecting stamps.

[6]Collecting stamps with themes is especially popular among teenagers because there is a wide range of choices for them. The main challenge is how you organize and expand your collection around your theme.

小题1:What is the main idea of the passage? (no more than 5 words)

___________________________________________________________________________

小题2:Fill in the blanks in Paragraph 2 with proper words. (no more than 5 words)

Of course, there are many ____________________________________________.

小题3:What should you do if you want to collect a full set of zodiac animal stamps? (no more than 7 words)

_______________________________________________________________________________

小题4:List the three general themes in collecting stamps mentioned in the passage. (3 words)

_______________________________________________________________________________

小题5:What does the word "them" (Line2, Paragraph6) probably refer to? (1 word)

_______________________________________________________________________________