共查询到20条相似文献，搜索用时 62 毫秒
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高志崇 《岱宗学刊(泰安教育学院学报)》2000,(3):38-40
本文根据电极反应有无氢离子参与分两种情况讨论了生化标准态电极势 E°′与热力学标准态电极势 E°间的关系。当电极反应无氢离子参与时 ,E°′=E°;当电极反应有氢离子参与时 ,E°′=(E°- 1.39× 10 - 3T) V。对于某些缺乏 E°值的电极 ,可通过反应的标准吉布斯自由能变△ r G°m 的值计算出 E°,然后利用公式计算出 E°′值。这样 ,我们便可借助于热力学标准态电极势 E°或反应的标准吉布斯自由能变△ r G°m 的值计算出某一温度下生化标准态电极势 E°′的值。通过计算得到的 E°′可更准确地反映出某一温度下生物体内电极的氧化还原能力 相似文献
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自由能—氧化态图是A、A、Frost于1950年首先提出来的,它是以金属单质为基准(△G°=0),在PH=0时各氧化态物质的标准吉布斯自由能(△G°)作为纵坐标,以其相应的氧化态值(N)作为横坐标的曲线图,通常简称为△G°—N图。例如,图一为锰元素的△G°—N图。这一图解对于元素的不同氧化态的水溶液化学性质都能给出明确的半定量的说明。本文在分析图象的基础上,总结规律,归纳该图在无机化学教学中的一些主要应用。 相似文献
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李君佐 《赣南师范学院学报》1989,(Z3)
ΔG变化值反映体系变化自发趋向的可能性、程度;当体系处于平衡时,应用化学等温式就可求算平衡常数K。将这一思路应用于溶液中的化学平衡,能很简结地得出与实验相当吻合的数据。为拓宽热力学在无机化学教学中的产用,必须在教学中增加ΔG°变化在溶液平衡中的产用,而这增加不作精密处理,采取直接引入的方法。 相似文献
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许盈 《中学数学教学参考》2001,(4)
一元二次方程是初中代数的一个极为重要的内容 ,尤其是判别式和韦达定理的应用更是广泛 ,成为初中数学竞赛的热点 .一、基础知识1 .判别式 .设一元二次方程ａｘ2 ｂｘ ｃ=0 ( )的判别式为Δ =ｂ2 -4ａｃ ,ｘ1、ｘ2 是方程的两个根 ,则Δ >0 方程 ( )有两个不等实根ｘ1,2 =-ｂ±Δ2ａ ;Δ =0 方程 ( )有两个不等实根ｘ1,2 =-ｂ2ａ;Δ <0 方程 ( )无实根 .2 .违达定理 .设ｘ1、ｘ2 是方程 ( )的两个根 ,则ｘ1 ｘ2 =-ｂａ ,ｘ1ｘ2 =ｃａ .特别地 ,当Δ≥ 0时 ,有ａｃ>0 两根同号 ,且 ａｂ>0 ,两根为负 ;ａｂ<0 ,两根为负 .ａｃ<0 … 相似文献
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定理 设ABCD为双圆四边形 ,R、r分别为外接、内切圆半径 ,r1、r2 分别为△ABC、△ADC的内切圆半径 ,则有R≥4r (r -r1) (r-r2 )r1 r2.①证明 :记AB =a ,BC =b ,CD =c,DA =d ,△ABC、△ADC的面积分别为Δ1、Δ2 ,四边形ABCD的面积为Δ ,半周长为 p ,则Δ1=12 r1(a b AC) ,Δ2 =12 r2 (c d AC) .由Δ =Δ1 Δ2 ,得2Δ =r1(a b) r2 (c d) AC(r1 r2 ) .由文 [1 ]知Δ =abcd ,R =14(ab cd) (ac bd) (ad bc)abcd12 ,∴AC =(ac bd) (ad bc)ab cd12 =4RΔab cd≤4RΔ2Δ =2R ,∴ 2Δ≤r1(a b) r2 (c d) 2R(r1 r2 )… 相似文献
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本文研究了以二(α—乙基己基)磷酸在磺化煤油——(Na,H)NO_3体系中萃取镍(Ⅱ)的机理及热力学性质。实验结果表明其机理为阳离子交换型:Ni~(2+)(a)+3H_2A_2 NiA_2·4HA(0)+2H~+(a).在298～323°K 温度区间里考察了温度 T 对萃取分配比 D 及萃取平衡常数 K_(jx)的影响,由1gK_(jx)～1/T 图中直线的斜率求出萃取反应的恒压热效应ΔH°为-15.7kj·mol~(-1). 相似文献
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《中国考试》2003,(Z1)
本试卷分第 卷 (选择题 )和第 卷 (非选择题 )两部分 ,满分 150分 ,考试时间 12 0分钟 .第 卷 (选择题 ,共 40分 )一、本题共 10小题 ,每小题 4分 ,共 40分 .在每小题给出的四个选项中 ,有的小题只有一个选项正确 ,有的小题有多个选项正确 .全部选对的得 4分 ,选不全的得 2分 ,有选错或不答的得 0分 .1.如果物体跟外界同时发生做功和热传递的过程 ,用 Q表示物体放出的热量 ,用 W表示物体对外界所做的功 ,用 Δ U表示物体内能的增加 ,则热力学第一定律可以表达为以下哪些形式 ( )A.ΔU=Q+ W B.Δ U=Q-W C.ΔU=W-Q D.ΔU=… 相似文献
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张一方 《商丘师范学院学报》2009,25(9):58-62
在重述负温度以后发现它必然导致熵减.负温度是基于Kelvin温标及条件dU>0和dS<0.反之,dU<0和dS>0时也是负温度.但是,负温度与通常温度的意义及物理和数学的某些基本概念是完全矛盾的.这是非平衡热力学中的一个问题.由此联系于孤立系统在一定条件下的熵减.热力学第二定律必然导致时间箭头和对称性破缺.熵减在一定程度将恢复熵变化的对称性.由对称性还讨论了推广的Noether定理. 相似文献
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目前,某些教科书在论述电池反应能否自发进行时,直接引用热力学判据ΔG=—zFE≤0 (1)即当E>0时,ΔG<0,说明该电池反应在所给条件下可以自发进行;当E<0时,ΔG>0,说明该电池反应在所给条件下不能自发进行。根据热力学基本原理,在恒温、恒压条件下,封闭体系中过程的方向和限度的 相似文献
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《海外英语》2007,(5):10-11
Many college freshmen arrive woefully unprepared to do college work, and as disadvantaged populations continue to grow, the share of the American work force that has made it through college is expected to plummet. Many experts blame that educational failure not just on high schools but also on colleges. School & College, a special report by The Chronicle, looks at efforts to fix the system. What reforms would better prepare students for college? What should schools and colleges be doing differently? How should state and federal officials help? 相似文献
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罗艳萍 《读与写:教育教学刊》2008,5(6)
The communication of people partially is the communication of cultures. Culture has a direct effect on international commercial activities in all aspects. Different conceptions about time, space, equality, law and the like, lead people to deal with things in different ways. So to know cultures of the counterpart is to facil-itate our enterprises so as to have a smooth and successful communication in commercial activity. 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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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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Richard Denner 《海外英语》2007,(4):14-15
Rosco and I wait for the fishermen to return.I sit at a wooden bench near the store at Mt.Baker Resort and watch the clouds change shape. Rosco has my belt around his neck and an eight foot tow chain hooked to a tree. Dogs must be on a leash. Ducks and rabbits are loose. 相似文献
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Given a graph G,a subgraph C is called a clique of G if C is a complete subgraph of G maximal under inclusion and |C|≥2. A clique-transversal set S of G is a set of vertices of G such that S meets all cliques of G. The clique-transversal number, denoted as TC (G), is the minimum cardinality of a clique-transversal set in G. The clique-graph of G, denoted as K (G), is the graph obtained by taking the cliques of G as vertices, and two vertices are adjacent if and only if the corresponding cliques in G have nonempty intersection. Let F be a class of graphs G such that F={G|K(G) is a tree}. In this paper the graphs in F having independent clique-transversal sets are shown and thus TC (G)/|G|≤1/2 for all G ∈ F. 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