题干

下列化学方程式符合题意,且书写正确的是(   )

A:氢气在空气中燃烧           H2+O2 __ H2O

B:用熟石灰处理污水中的硫酸   Ca(OH)2+H2SO4═CaSO4+H2O

C:用碳酸钠溶液制烧碱         Na2CO3+Ca(OH)2═CaCO3↓+2NaOH

D:用稀硫酸除铁锈             2H2SO4+Fe2O3═2FeSO4+2H2O

上一题 下一题 0.0难度 选择题 更新时间:2017-09-06 12:48:57

答案(点此获取答案解析)

C

同类题1

阅读下文,回答相关问题。

                                                                                                           成长不可无书
      ①这是中央电视台记者在采访中与一个西北放羊娃的对话:
      ②“你每天干什么?”“放羊。”“放羊为了什么?”“挣钱。”“挣了钱呢?”“娶媳妇。”“娶了媳妇呢?”“生娃。”“生了娃,让他干什么?”“放羊。”……
      ③这样的回答我并不奇怪,但当我从一张报纸的公益广告上,实实在在地看到这串白纸黑字的记录时,我的心仍然被强烈地震动了。
      ④穷文富武曾是中国的传统,家贫,只能通过读书出人头地。然而,不能否认的是,在今天的中国,也还有一大批像放羊娃一样的孩子,安贫若素。
      ⑤这不禁令我想到一句格言:生命的悲哀不在于目标未达成,而在于没有目标可达成。在那没有知识光亮闪耀的地方,生命便永在“放羊——下一辈还放羊”的循环中延续。
      ⑥据说在美国历史上曾有这样两个家族。一个是爱德华家族,其始祖爱德华是位满腹经纶的哲学家,他8代子孙中出了13位大学校长。100多位教授。80  多位文学家。20多位议员和一位副总统;另一个家族的始祖叫珠克,是个缺乏文化修养的赌徒和酒鬼。他8代子孙中有300多名乞丐。7个杀人犯和60多个盗窃犯。一个人有没有文化修养,竟可以产生如此源远流长的影响,这不禁又使我想起中国“希望工程”中的两句宣言:再穷不能穷了教育,再苦不能苦了孩子。
      ⑦“自己再累也要读书,工作再忙也要读书,收入再少也要买书,住处再挤也要藏书,交情再浅也要送书。”这是几年前台湾知识分子倡导的“新读书主义”。饥之以当食,寒之以当裘,忧患以当安乐,孤寂以当金石琴瑟也。读书,实在是我们今天应该大力弘扬的好传统。
      ⑧成长不可无书,成功不能无知。一切渴求成长、成功、成熟的朋友,请把高品质的书籍报刊请到你的身边,终身相伴,终生受益。

同类题2

阅读理解

    You may be surprised to learn that English gets 30 to 45 percent of its words from French. The reason goes back to the year 1066, when Norman forces invaded(入侵)what is now Britain. The Normans were from northern France and spoke French. During the Norman occupation, French became the language of England's rulers and wealthy class. This lasted for more than 300 years. Other people in England continued to speak English during this period.

    Over time, the two languages combined and shared words. Some researchers believe that about 10,000 French words eventually entered the English language. However, although English took many French words, their meanings have not always stayed the same. Sometimes the differences in meanings can be very important, and lead to funny or strange situations if the words are used in the wrong way.

    Take, for example, the French word college. In English, college can often be used in place of the word university, or sometimes as a school within a university. However, in French, college actually means “middle school”, or the level of schooling for students in grades five or six through eight.

    There are many other similar words in the two languages with completely different meanings. In English, the word chat is a verb which means “to talk casually”; but in French, the word chat is the word for an animal: a cat.

    If an English speaker says someone is jolly, that means they are cheerful or friendly. But in French, jolie means someone is good-looking or pleasant to look at. In any case, both are nice things to say to someone.