题干

下列说法、方程式以及基本反应类型均正确的是(   )

A:用赤铁矿石炼铁    3CO+Fe2O3 __ 2Fe+3CO2    置换反应

B:溶洞的形成    CaHCO3=CaCO3↓+H2O+CO2↑    分解反应

C:正常雨水的pH约为5.6的原因    CO2+H2O=H2CO3    化合反应

D:用熟石灰处理盐酸厂的废水    Ca(OH)2+HCl=CaCl2+H2O    复分解反应

上一题 下一题 0.0难度 选择题 更新时间:2016-04-13 12:03:15

答案(点此获取答案解析)

C

同类题2

阅读理解

    I look around and can't recognize where I am. It seems familiar but distant. I see my friends gather by a stage where music is playing and I run over. As I begin running towards them, they become further and further away. I keep calling them, but no one hears me. I start hearing a distant alarm-like sound and I am transported away. I woke up in a daze sitting in my bed.

    “Oh, it was only a dream,” I said to myself. I have always had vivid and intense dreams. It feels like I haven't even slept because I have been living out my dreams during my sleep.

    Today, dreaming is being studied even more than ever. Some say that dreams are how your receptors make sense of random thoughts while you sleep. Some say that you can't dream of a face you have never seen before, so everyone you see in your dreams you have at least laid eyes on at one time or another.

    Other people think dreams are ways of expressing stress or internal feelings you may be experiencing. A lot of people say that they have dreams about being chased.

    A common interpretation of the “being chased” dream is that you are feeling threatened. Some dream interpretation websites say you should try to reflect on what or who is chasing you to get a better idea of what is making you feel this way.

    Another dream that is often experienced is flying. This dream has a much more positive interpretation, which is that you are feeling free or have broken out of a bad situation such as a relationship turned sour or a job you hate.

Unfortunately, you may forget half of your dream within five minutes of waking up and within 10 minutes, you usually forget 90 percent of it.

    Dreamologists, people who devote time to the study and interpretation of dreams, suggest if you want to try to remember and study your dreams you should keep a journal beside your bed and write down what you dreamt as soon as you wake up so you can reflect on it later.

同类题3

阅读以下材料,说说以下化学探究活动是由哪些环节组成的,将其分别填在相应的括号内.

燃烧是我们经常接触到的一种化学变化.它与我们的生活密切相关.燃烧为人类带来了光明,如果失控也会给人类带来灾难.因此,人类必须了解物质为什么会燃烧,才能控制燃烧,使其更好地造福于人类.

小童想:物质燃烧需要哪些条件?(____ )

(1)可能需要一种可以燃烧的物质;

(2)可能需要一定的温度;

(3)可能需要氧气.(____ )

小童设计了实验方案:

实验1:用镊子分别夹取一小木条和小石子,将它们分别放在酒精灯外焰上加热,观察实验现象.

实验2:用镊子分别夹取一小纸片、小木条、小煤块,分别在酒精灯上点燃,观察实验现象,比较三者点燃的难易程度.

实验3:在桌面上点燃两支蜡烛,在一支蜡烛上方罩上250mL烧杯,观察实验现象.(____ )

小童对实验现象进行了记录和分析:


实验现象

得出的结论

 实验1

小木条燃烧了,小石子不燃烧.

燃烧需要可燃物

 实验2

小纸片最易燃烧,小木条次之,小煤块最难燃烧.

燃烧需要达到可燃物燃烧所需的温度.

 实验3

 桌面上的蜡烛正常燃烧,罩上烧杯的蜡烛燃烧一会儿就熄灭.

 燃烧需要氧气.

小童归纳总结,得出燃烧的条件:可燃物;温度;氧气.(____ )

小童觉得,通过这次探究活动,知道了燃烧的条件,能解释钻木取火、森林灭火等现象和原理,并且体验了像科学家一般探究学习的乐趣.(____ ).