共查询到20条相似文献,搜索用时 46 毫秒
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邱峻 《中学生数理化(高中版)》2008,(10):70-72
新制氯水是由Cl2、H2O、HClO和H^+、Cl、ClO^-及少量的OH^-组成的混合物.氯水的多种成分决定了它具有多重性质:①Cl2的强氧化性;②HClO、ClO^-的强氧化性;③HCl的强酸性;④HClO的弱酸性;⑤Cl^-的性质.在不同的反应中,氯水中起作用的成分不同,一般有以下6种情况. 相似文献
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氯气溶于水形成的溶液叫氯水。新制的氯水呈黄绿色,有刺激性气味。在氯水中存在以下反应:Cl2+H2O!HCl+HClO;HClO!H++ClO-;HCl=H++Cl-;2HClO2HCl+O2↑;H2O!H++OH-。所以在新制氯水中存在三种分子:Cl2、H2O、HClO;四种离子:H+、Cl-、ClO-及少量的OH-。可见,新制氯水的成分是复杂的。新制氯水成分的复杂性,决定了其性质的多重性。在化学实验中,可以利用这些性质来替代一些化学试剂。主要有以下几个方面:(1)利用Cl2的性质①强氧化性Cl2是一种实验中常用的气体强氧化剂,但贮存起来很不方便,需随用随制,一般可用新制氯水替代。… 相似文献
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刘丽娟 《中学生数理化(高中版)》2005,(9):84-85
知识要点:常温常压下,1体积水中大约可溶解2体积Cl2,Cl2溶于水后,可部分与水反应Cl2 H2O==HCl HClO,氯水中存在的粒子有H2O、Cl2、HClO、H 、Cl、ClO-、OH,共七种.氯水与不同物质反应时,参加反应的粒子不同,现象不同,表现出的性质也不相同. 相似文献
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氯气溶于水形成的溶液叫氯水。新制的氯水呈黄绿色,有刺激性气味。在氯水中存在以下反应:Cl2+H2O→←HCl+HClO;HClO→←H^++ClO^-;HCl→←H^++Cl^-;2HClO=^光2HCl+O2↑;H2O→←H^++OH^-。所以在新制氯水中存在三种分子:Cl2、H2O、HClO;四种离子:H^+、Cl^-、ClO^-及少量的OH^-。 相似文献
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传统的实验室制备氯水装置,存在易逸出氯气、氯化氢污染环境,影响师生的身心健康等缺点,实验装置经改进后,能有效克服和避免以上不足. 相似文献
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本节课是全日制普通高中化学(试验修订本,必修)第一册第四章《卤素》第~节《氯气》的第一课时。为了适应基础教育新课程的发展,在课堂教学中通过学生的探究过程,让学生了解“探究过程”的一般思路,培养学生的探究精神,我将这节课的教学过程设计如下: 相似文献
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Talking about mathematics 总被引:1,自引:0,他引:1
Gilah C. Leder 《The Australian Educational Researcher》1990,17(2):17-27
Students in a grade 3 class in a primary school in an outer suburb of Melbourne were encouraged to talk about, and ultimately reflect on, the work they had learnt in mathematics. Four lessons, each of approximately 50 minutes duration, were videotaped. Key excerpts were subsequently replayed to the children in a one-to-one setting. The data presented focussed on a lesson aimed to extend the children’s knowledge of fractions beyond a half and a quarter. By tracing the responses of four students in particular, two low and two average achievers, substantial individual differences in the ways children constructed meaning out of shared mathematical experiences were identified. The investigation confirmed that listening to students talk about their own mathematical experiences provides a rich data base for investigating students’ learning, error analysis, and subsequent teaching. 相似文献
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1.What a lovely day it is!The sun is shining beautifully.The sky is so blue.2.It’s fairly(相当)warm for this time of the year.3.Let’s hope it will keep fine for the weekend.4.The weather is changing.I’m afraid.5.I think it’ll turn out a wet day(要下雨).6.The air is close(沉闷).The clouds are very heavy(厚).7.The clouds are gathering.The sun has gone in(被遮).It’s getting quick 相似文献
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Janet Evans 《Education 3-13》2013,41(1):66-71
This article looks at why talk is important for young children learning mathematics, how talk fosters mathematical understanding and the importance of having something to talk about by relating maths to real situations. It then looks at the revealing comments of some four and five year old children talking about simple number activities linked to a favourite rhyming story song they had been singing. 相似文献
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英语语言最重要的特征之一便是一词多义,在众多意义中选择既忠实原文又符合汉语表达习惯的译词,实为不易。而英汉翻译中的文化障碍或文化空缺现象对翻译也带来很大的困难。该文文在翻译过程中使用"一词多译"、"词类转换"和"文化空缺"的补偿手段方面作了认真的探讨。 相似文献
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在以农耕生产为主的中国古代,“雨”在人们的生活、思想领域起着重要作用。从甲骨卜辞起,人们由对雨的崇敬惧怕的心理而开始占卜。最初,只是对“是否下雨”等自然状况的占卜,随着文化的发展,占卜的内容也日益深化。 相似文献