共查询到20条相似文献，搜索用时 62 毫秒
1.
一、单质与单质之间1.多数金属和非金属之间可以直接化合生成无氧酸盐,多数在加热的情况下进行,但有的产物不属于盐.如2Fe 3Cl2△2FeCl32Na S△Na2S3Mg N2点燃Mg3N2(氮化物)2.多数金属、非金属跟氧直接化合生成氧化物(Al2O3为两性氧化物,Na2O2为过氧化物,CO、NO为不成盐氧化物) 相似文献
2.
例1在由Na2S、Na2SO3、Na2SO4组成的混合物中钠元素的质量分数为46％，氧元素的质量分数是多少？[第一段] 相似文献
3.
现行高中课本第一册学生实验六，同周期、同主族元素性质的递变中，用氢硫酸加氯水，有单质硫析出，溶液变浑浊，说明同周期元素性质的递变。我改用Na2S溶液代替氢硫酸，把氯水改成用盐酸酸化的氯水，经实践证明有以下几个好处：一、现象更加明显，效果更好。因氢硫酸浓度太小（约0．1mol／L左右），又是弱电解质，单位体积中所含S2－浓度更小。而硫化钠属强电解质，Na2S溶液全部离解，S2－浓度大，所以实验中的浑浊现象非常明显。二、氢硫酸不稳定，不便保存。三、在实验室需用Na2S或FeS等来制取氢硫酸，如果直接用硫化钠溶液，就可以… 相似文献
4.
5.
滑线变组器在电学中是一种常用的器材,学生使用时经常盲目照搬现成结论,不能因题而异.因此教学中有必要对此解释透彻.l 作为分压用途滑线变组器的接法[例1]如图1所示,滑线变组器R_1的最大阻值为200Ω,R_2为200Ω,AB两端的电压为8V,当开关S断开时,移动滑动触头P,R_2两端可获得的电压值的范围是___V,当S闭合时,R_2两端可获得电压值的范围是_____v.[解析]当开关S闭合时,整个电路是分压器接法.P滑到R_1的b端时,R_2被短路;P滑到R_1的a端时,R_2和R_1并联.电压的变化范围是0～8V. 相似文献
6.
米-门(Michaelis-Menten)方程表示的是一条矩形双曲线。一般把米-门方程表示为:v=(V[S])/(K_M+[S])或 K_M=[S]((V/S)-1)式中,v 表示酶催化的化学反应速度,[S]表示底物浓度,V 表示在酶浓度一定时的最大反应速度,K_M 表 相似文献
7.
《新疆教育学院学报》1997,(1)
在阴离子定性分析中用1％的Na2[Fe（CN）_5NO]溶液鉴定S(2-)离子，其鉴定反应如下但由于该溶液不稳定，不便存放，在光照下变质更快。笔者以Na2[Fe（CN）5NO]的制备反应[2]为依据，对实验现象进行分析，认为加入适量的亚硝酸盐，可以提高Na2[Fe（CN）5NO]水溶液的稳定性。1实验 相似文献
8.
《赤峰学院学报(自然科学版)》2021,(9)
运用太阳能进行可见光催化二氧化碳还原是实现碳中和目标的有效途径。如何培养具有专业素养的环境治理人才是本科院校重要研究方向。本文以In_2O_3/Zn_(0.5)Cd_(0.5)Se异质结材料的合成为媒介,采用X射线衍射仪、扫描电子显微镜及二氧化碳光催化还原测试等方法研究In_2O_3/Zn_(0.5)Cd_(0.5)Se复合材料的合成方法、物相成分、形貌状态、化学组成及在碳中和领域的应用。该研究表明,以球形花状的In_2O_3纳米球作为基底材料,通过与Zn_(0.5)Cd_(0.5)Se复合得到的In_2O_3/Zn_(0.5)Cd_(0.5)Se异质结材料拥有更高的CO_2转化CO性能。通过该创新实验的设计,能够更好地培养材料类专业人才。 相似文献
9.
有这样一道初中化学竞赛试题：一在Na2S、Na2SO3、Na2SO4的混合物中,S占25．6％,则氧的百分含量为（）A．37．6％B．36．8％C．51．2％D．无法求解[分析]这是一道关于元素百分含量的计算题．它所涉及的知识非常简单,在初中化学中学生就已全部学过．[常规解]设混合物中含有X克Na2S、Y克Na2SO3、Z克Na2SO4,根据有关知识可以得到：上述联立方程组中一共有6个变量：S％、O％、Na％、X、Y、Z;但只有5个独立方程．任何寻求第六个方程的努力都是徒劳的,根据有关数学理论,我们不可能求出它们独立的解。值得欣慰的是,本题的情况… 相似文献
10.
一、单项选择题 1.两个质量均为m,带电均为 q的小球,用等长的丝线悬挂在同一点,平衡时如图所示。若两悬线间张角为2θ,则小球所在处的电场强度E的大小为:[ ] A.mg/qtgθ;B.mgsinθ/q C.mgtgθ/q;D.mgcosθ/q。 2.带电量为q的粒子,以一定的速率垂直射入匀强磁场中形成空间环形电流,当粒子的速率增大时,环形电流的大小将:[ ] A.变大; B.变小; C.不变; D.无法判断。 3.一个有内阻的电源两端接上一只“6V、6W”的小灯泡时,灯泡恰能正常发光,若改接“6V、3W”的小灯泡,其实际消耗的功 相似文献
11.
12.
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
13.
《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
14.
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
15.
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
16.
17.
RUZBEHANI Mohsen 《重庆大学学报(英文版)》2004,3(1):20-25
1.IntroductionOne-cyclecontrolmethod,whichwasproposedaboutonedecadeago[1],hasbecomeanattractivemethodinspecialfieldssuchaspowerfactorcorrection[2-6],switchingamplifiers[7,8],etc.Themainideaofthiscontrollerisbasedonintegrationofdiodevoltageinone-cycleandforcesittobeexactlyequaltothereferencevalue.Themainadvantageofthiscontrollerisitsrealtimeabilitytorejectthevariationofinputvoltage[1].Despitethisgreatability,ithasnogoodperformancesinrejectingofloaddisturbanceandfollowingreferencecommands.Espec… 相似文献
18.
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
19.
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
20.
Rajesh Kanoi 《海外英语》2007,(1):52
Today, Sunday morning, I sit thinking and typing at my computer. My thoughts are in my homeland, India and my body is in China. The body is here and mind there for a good reason. Mr. Hu is president and I am resident and both are in each other's countries (what a difference the absence of one small letter makes!). Mr. Hu will return in a few days and I will stay on longer. 相似文献