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李立芬 《中学生数理化(高中版)》2005,(13)
水的电离和溶液pH是电解质溶液知识体系的灵魂,理解和熟练掌握有关的基本知识是参透电离平衡理论的保证. 1.水的电离和水的离子积常数水是一种极弱的电解质,它能微弱地电离生成H3O+和OH-,通常简写为H+和OH-.其中c(H+)·c(OH-)=Kw,Kw称为水的离子积常数,简称为水的离子积.其意义是:在一定温度下,水溶液中c(H+)和c(OH-)之积为一常数.由实验测知,在25℃时,1 L纯水中只有约1×10-2mol H2O电离,所以,c(H+)=c(OH-)=1×10-7mol·L-1,因此,在25℃时,Kw=c(H+)·c(OH)=1×10-7×1×10-7=1×10-14(此时的 相似文献
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《第二课堂(小学)》2005,(1)
一、题型归纳 一、关于盐对水的电离的影响的试题 例l室温下,在PH=12的某溶液中,由水电离的c(OH)为() A .1 .Oxlo一mol·LI B.1.Oxlo巧xnol·Ll C .l.oxloesZmol·Ll D.l.oxlO一12mol·Ll 解析若该溶液为碱溶液,则由于碱的OH一的抑制了水的电离,由水电离出的。(OH一)=l .oxlo一1知ol·L,;若该溶液为水解呈碱性的盐溶液,则由于其中弱酸阴离子结合了水中的H十,促进了水的电离,故由水电离的。(OH一)二l.oxlowe、nol·L--,。因此答案为C、D。 例2在PH都等于9的NaOH和CH3COONa溶液中,设由水电离产生的离子浓度分别为A mol·L一,… 相似文献
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化学规律是在解决化学问题中总结出来的 ,这些规律作为一种工具 ,在解决新问题时能事半功倍。2 0 0 2年高考化学试题集中反映了这一点。一、弱电解质的电离规律规律 :对于一元弱酸 (或一元弱碱 )的溶液 ,溶液中各种关系如表 1所示。表 1 一元弱酸 (或一元弱碱 )溶液的各种关系电 离方程式 ＨＡ Ｈ++Ａ- ＭＯＨ Ｍ++ＯＨ-[Ｈ+](或 [ＯＨ- ])与电离度α的关系 [Ｈ+]=ｃａ·α [ＯＨ- ]=ｃｂ·α溶液 ｐＨ与电离度α的关系 10 - ｐＨ=ｃａ·α 10 ｐＨ=10 14 ·ｃｂ·α 例 1 .0 .0 1ｍｏｌ·Ｌ- 1的某一元弱酸溶液 ｐＨ =4,则它的电离… 相似文献
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盐溶液中不仅存在着盐的电离、水的电离,还存在着某些离子的水解,溶液中的离子浓度间的关系较复杂。其实,在任何电解质溶液中微粒间都存在着一定的守恒关系,例如,在0.1mol·L-1的Na2S溶液中存在着下列电离和水解:Na2S=2Na++S2-,H2OH++OH-,S2-+H2OHS-+OH-,HS-+H2OH2S+OH-。一、电荷守恒任何电解质溶液都是电中性的,因此,溶液中阳离子的总电荷量与阴离子的总电荷量的绝对值相等。例如,在0.1mol·L-1的Na2S溶液中有下列关系:c(Na+)+c(H+)=2c(S2-)+c(OH-)+c(HS-)。二、物料守恒电解质溶液中,由于某些离子的电离或水解,使某种元素… 相似文献
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电解质在溶液中的行为是每年高考必考的高中化学理论知识之一.当电解质溶于水时,在溶液中首先是会发生电离,而电离又可能是部分电离,可能是完全电离;其次电解质电离形成的离子在溶液中还可能会发生水解,从而使溶液中的各种离子浓度、分子浓度及溶液的pH值等发生变化. 相似文献
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一、水的电离和水的离子积常数水是一种极弱的电解质,它能微弱地电离出H3O+和OH-:H2O+H2OH3O++OH-(简写为H2OH++OH-)。这种电离方式的本质是“质子(即H+)转移”。其中c(H+)·c(OH-)=KW,KW称为水的离子积常数,简称为水的离子积。其意义是:一定温度下,水溶液中c(H+)和c(OH-)之积为常数。由实验测知,在25℃时,1L纯水中只有约1×10-7molH2O电离,所以,c(H+)=c(OH-)=1×10-7mol·L-1。因此,在25℃时,KW=c(H+)·c(OH-)=1×10-7×1×10-7=1×10-14(此时水的pH=7,呈中性)。值得注意的是,KW是温度函数,只随温度升高而增大(与溶液浓… 相似文献
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高中化学课本第三册第二章第一节中有这样一段话:“离子化合物和某些具有极性键的共价化合物在水溶液里全部电离成离子,没有分子存在。所以,不存在分子和离子间的电离平衡,这样的电解质属于强电解质。强电解质在水溶液里全部电离为离子。……某些具有极性键的共价化合物的水溶液里只有一部分电离成为离子,还有未电离的电解质分子存在,分子和离子之间存在着电离平衡。这样的电解质属于弱电解质。弱电解质在水溶液里只有部分电离成为离子。”对于这段话究竟应当怎样正确理解,本文似做一简要讨论。 早在1887年阿累尼乌斯提出了关于电解质溶液的第一个定量理论。后经奥斯特瓦尔德等科学家进一步发展和充实,形成了阿累尼乌斯电离学说。该学说的基本论点可以归纳成下面三点: 相似文献
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电解质溶液中离子浓度大小比较问题是高考的热点,也是学习的难点.现结合一些典型例题对常见类型进行梳理,以明确解题思路.类型一单一溶液中各离子浓度的比较(1)弱电解质的电离是微弱的.多元弱酸溶液分步电离,电离程度逐级减弱.如H3S溶液中:c(H2S)>c(H+)>c(HS-)>c(S2-).(2)弱电解质离子的水解是微弱的(双水解除外).多元弱酸的正盐溶液中,弱酸根离子分步水解,水解程度逐级减弱.如 相似文献
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题型示例一 :盐对水电离的影响【例 1】 室温下 ,在pH =1 2的某溶液中 ,由水电离的c(OH- )为A .1 .0× 1 0 - 7mol·L- 1 B .1 .0× 1 0 - 6 mol·L- 1C .1 .0× 1 0 - 2 mol·L- 1 D .1 .0× 1 0 - 12 mol·L- 1解析 :若该溶液为碱溶液 ,由于碱的OH- 抑制了水的电离 ,此时由水电离出的c(OH- ) =1 .0× 1 0 - 12 mol·L- 1;若该溶液为水解呈碱性的盐溶液 ,则由于其中弱酸阴离子结合了水中的H+,促进了水的电离 ,故由水电离的c(OH- ) =1 .0× 1 0 - 2 mol·L- 1.答案应为C、D .方法精要 :水的电离平衡为 ,H2 OH++OH- ,根据… 相似文献
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邱崇丙 《唐山师范学院学报》2014,(1):21-23
汉字的六书,《说文》对“转注”一类,语焉不详。后世学者提及转注,也仅限于许慎所举出的例字。《汉字例说》一文,作者从转注的角度综合考虑,对部分现代常用字作了分析,跟传统的解释有所不同。希望能抛砖引玉,互相切磋,以推进学术研究。 相似文献
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Rachel Zupek 《海外英语》2007,(11):40-41
我们绝大部分人都同意一件事情——我们喜欢金钱。但是你对金钱的喜欢之情足够到让你创立一份事业么?.财富通常被人忽视,主要在于人们不能真正了 相似文献
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《海外英语》2007,(4):36
There are numbers of crossroads on our long and unpredictable life journey where we totally have no idea about which direction to choose. No matter what our decision is, we should not turn back, but face the music and go ahead instead. I am this kind of girl who always does try without regretting, one example is how I dealt with my love. 相似文献
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YANGShiguo 《重庆大学学报(英文版)》2004,3(1):86-88
The problem on the geometrc inequalities involving an n-dimensional simplex and its inscribed simplex is studied. Aninequality is established, which reveals that the difference between the squared circumradius of the n-dimensional simplex andthe squared distance between its circumcenter and barycenter times the squared circumradius of its inscribed simplex is not lessthan the 2(n-1)th power of n times its squared inradius, and is equal to when the simplex is regular and its inscribed siplex is atangent point one. Deduction from this inequality reaches a generalization of n-dimensional Euler inequality indicating that thecircumradius of the simplex is not less than the n-fold inradius. Another inequality is derived to present the relationship betweenthe circumradius of the n-dimensional simplex and the circumradius and inradius of its pedal simplex. 相似文献
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Migration occurs behind a variety of reasons and has a great effect on the whole world. People may migrate in order to improve their economic situation, or in order to escape civil strife, persecution, and environmental disasters. The impact of migration is complex, bringing both benefits anddisadvantages. This paper briefly talks about the causes of migration, the allocation of benefits, and the ways in which individual countries and the international community deal with this important subject. 相似文献
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GUO Bao-feng Xiao Da-wei 《重庆大学学报(英文版)》2005,4(3):129-133
Using virtual reality for interactive design gives a designer an intuitive vision of a design and allows the designer to achieve a viable, optimal solution in a timely manner. The article discusses the process of making the Virtual Reality System of the Humble Administrator＇s Garden. Translating building data to the Virtual Reality Modeling Language （VRML） is by far unsatisfactory. This creates a challenge for computer designers to do optimization to meet requirements. Five different approaches to optimize models have been presented in this paper. The other methods are to optimize VRML and to reduce the file size. This is done by keeping polygon counts to a minimum and by applying such techniques as object culling and level-ofdetail switching. 相似文献
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The awareness of individualism can be traced back to the period of American Revolution when the Declaration of Independence was produced.It expressed basic beliefs concerning freedom,equality,democracy,privacy and the relationship between people and government,which were exactly what the philosophy of individualism mostly dealt with at that time.This paper is to exploit the essence of individualism by analyzing the Declaration .The analysis enables us to reconsider its significance to the issue of America human rights and foreign policies. 相似文献
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Sister Carrie is one of the most controversial characters in American literature.Thought as a "fallen woman" firstly,she was defined as a "new woman" by some critics later. However, by digging into the motivaton behind the whole process of Carrie's "success", the relationship between Carrie and her creator (the author), the social conditions of then American, it can be found that Carrie has never been free-standing on her thought and she has never found her real-sdf even after becoming a famous actress. In a society dominated by mass consumerism Carrie is only an adherent of her own desires. She also is a representative of all those country girls flooded into cities, a symbol and a sacrifice of the urbanization of America in a time countryside was overcome by cities. 相似文献