《分析化学》阅读材料03 摘自Analytical Chemistry (FECS)
●In the Br?sted-Lowry theory, an acid is a proton donor and a base is a proton acceptor. Each acid is related to its conjugate base and vice versa:
Acid = base + proton
Therefore, the conjugate base of a strong acid must be a weak base and the conjugate base of a weak acid must be a strong base. Together they form a couple, and an acid without its conjugate base is a meaningless concept. In order to release a proton, the acid must find a base to accept it. In an aqueous solution, the proton, H+, having an extremely small ionic radius, cannot exist as such. It is hydrated, forming the hydronium ion H3O+ and higher hydrates. Thus, an acid-base equilibrium is not a simple dissociation equilibrium, but the result of a proton transfer reaction in which there are at least two reagents and two products. Such a process is also called protolysis. The overall reaction is expressed by: HX + H2O = H3O+ + X-. The overall equilibrium constant is
K = [H3O+][X-]/[HX][H2O].
The acid dissociation constant Ka is given by: Ka = K[H2O] = [H3O+][X-]/[HX]. Ka reflects not only the acid strength of HX, but also the base strength of water. This why different acid dissociation constants are observed for the same acid in different solvent.
●Similar proton transfer reactions exist in all solvents possessing proton donor and acceptor properties. Proton transfer reactions are extremely fast. This makes them very suitable for analytical applications and acid-base reactions have found wide use in volumetric methods and other analytical techniques.
●The pH value is a measure for the acidity or basicity of a solution, aqueous or nonaqueous.
●Acid-base indicators are chemical substances with acid-base properties, having different colors in their protonated and deprotonated forms.
● A most important application of acid-base systems is related to the property of such a system to act as a buffer. Many chemical reactions produce protons (in aqueous solutions hydroniums) or hydroxide ions. If these products remain in the system, a corresponding pH change is observed. However, if a buffer is present in the solution it reacts with the liberated hydrogen or hydroxide ions so that only a relative small change of pH occurs. Buffer consist of a mixture of a weak acid and its conjugate base. The most efficient buffer for a given pH consists of a 1:1 ratio of the protonated and deprotonated forms of a weak acid (with pKa = pH). This cannot always be achieved, but if we wish to prepare a solution of a certain pH, we select a weak acid with a pKa value close to the desired pH. Buffer solution resists changes in pH upon adding of strong acids or strong bases. Depending on the relative concentrations of the acid and base forms of the buffer, the system can resist small or large additions of strong acid or base. This buffer capacity is defined as the number of moles of strong acid of base required to change the pH of 1 L of buffer solution by one pH unit. Solutions with high or low pH values, formed as a result of dissolution of large quantities of a strong base or acid, are characterized by a large buffer capacity, although the electrolyte practically consists of only one of the conjugate forms (e.g., HCl or NaOH solutions).
● A general requirement for all volumetric methods is that the titration process is fast and that it proceeds in a definite stoichiometric ratio, the endpoint of the reaction must by easy to detect and the reaction should be specific and not influenced by other constituents of the solution, i.e., there should be no interference. Question:
1. A H3PO4 solution is brought to pH = 7.00 by the addition of NaOH. Calculate the concentration of the various
forms of orthophosphate if the total phosphate concentration in buffer is 0.200 mol /L. pKa1 = 2.16, pKa2 =
7.21, pKa3 = 12.32.
2. A buffer solution is prepared from acid, HA, Ka = 5 10-5, and its salt. The concentration of HA in the buffer
is 0.25 mol / L. To 100 mL of the buffer added 5.0 mmol of NaOH, and the pH of the resulting solution is
5.60. What was the pH of the original buffer?
3.It is desired to change the pH of 100 mL of 0.100 mol / L HCl from 1.00 to
4.40 by the addition of sodium
acetate, CH3COONa3H2O. How much solid sodium acetate salt must be added in grams? Assume no volume change for the solution as the result of the addition.
4.What is the buffer capacity of a solution which is 0.100 mol / L of NH3 and 0.200 of NH4Cl?
5.Calculate the pH of each of the following solution: (a) Water in equilibrium with CO2 of the air; pKa1 =
6.38,
pKa2 = 10.25. (b) Water as in part (a) brought to pH = 7.00 with NaOH and allowed to regain equilibrium with CO2.
6. Derive the following expression for the pH at the first stoichiometric point in the titration of a mixture of two
weak acid: HA, the stronger, Ka1, concentration C1; HB, the weaker, Ka2, concentration C2:
pH = 1/2 (pKa1 + pKa2) – 1/2 lg (C1/C2)
Fast Reading Materials for Senior I完形填空（共 20 小题；每小题 1.5，满分 30 分） 阅读下面短文，掌握其大意，然后从 36~55 各题所给的四个选项（A、B、C 和 D）中，选出最佳选项，并在答题卡上将该项涂黑。 While I studied at school, I felt a great difficulty in learning my Latin translations. I was always very 36 in using a dictionary, and 37 it most difficult, while to other boys it seemed no 38 . I formed an alliance（盟友）with a boy in the Sixth Grade .He was very clever and 39 read Latin as easily as English .My friend for his part was almost as 40 troubled by the English essays he had to write for the headmaster as I was 41 these Latin words .We agreed together that he would 42 me my Latin translations and that I should do his essays. The arrangement 43 wonderfully. The headmaster seemed quite 44 with my work, and I had more time to myself in the morning. On the other hand, once a week 45 I had to compose the essays of my friend. For several months no difficulty 46 , but once we were nearly caught out. One afternoon, the headmaster 47 my friend to discuss one essay with him in a lively spirit. “I was interested in this48 you make here. I think you might have gone further .Tell me 49 you had in your mind.” The headmaster continued in this50 for some time to the fear of my friend. However the headmaster, not wishing to 51 an occasion of praise into 52 of fault-finding, finally. 53 him go. He came back to me like a man who had had a very narrow 54 and I made up my mind to make every effort to study my 55 . 36．A．quick B．slow C．hard D．good 37．A．made B．got C．found D．left 38．A．trouble B．difference C．labor D．worry 39．A．might B．would C．should D．could 40．A．very B．little C．much D．few 41．A．for B．by C．in D．to 42．A．change B．take C．forgive D．tell 43．A．worked B．tried C．happened D．developed 44．A．angry B．satisfied C．frightened D．sad 45．A．or so B．or else C．as usual D．as far 46．A．became B．seemed C．lay D．appeared 47．A．called B．taught C．arranged D．sent 48．A．aim B．goal C．point D．opinion 49．A．why B．how C．which D．what 50．A．excitement B．way C．meaning D．disappointment 51．A．turn B．leave C．grow D．become 52．A．none B．one C．either D．some 53．A．ordered B．asked C．took D．let 54．A．surprise B．escape C．hope D．chance 55．A．reading B．writing C．translations D．essays II 阅读理解
阅读理解中约有60%以上的题能再原文中找到答案，其余就要考一下推理、逻辑等能力。阅读一定要先看题目，带着问题去文中找答案，尤其是在快速阅读题部分更是非常重要。还有就是要留心各个大小标题。（出题者常以依次而下的顺序出题，而且每题基本都是细节题，分别对应文章一段，可以采用关键词定位的方法），坚持每天都要练习。 提高阅读水平，在阅读理解上拿高分，是四级必过的又一大支柱。阅读理解的复习方法及答题技巧： 四级大纲要求能基本读懂一般性题材的英文文章，阅读速度达到每分钟70词。在快速阅读篇幅较长、难度略低的材料时，阅读速度达到每分钟100词。能基本读懂国内英文报刊，掌握中心意思，理解主要事实和有关细节。能读懂工作、生活中常见的应用文体的材料。能在阅读中使用有效的阅读方法。 四级的阅读理解主要：快速阅读理解和仔细阅读理解。快速阅读部分要求考生在15分钟的时间内读完一篇1100字左右的文章和后面的10道题。前面7道题是单项选择题，后3道是填空题，即根据对阅读材料的理解，填3到4个单词或短语(答案基本都是原文中出现的原词)。 仔细阅读部分要求考生阅读三篇短文。两篇为单项选择题型的短文理解测试，一篇为选词填空。仔细阅读理解部分测试考生在不同层面上的阅读能力，包括理解主旨大意和重要细节、综合分析、推理判断及根据上下文推测词义等。
大学英语四级考试的阅读文章体裁有记叙文、说明文、议论文，其中说明文和议论文为主要测试文体；在阅读题材方面，科技类大约占25%，人文类大约占45%，经济类大约占15%，综合类大约占5%，环境类比例小，近几年有上升趋势。因此，学生应针对不同的体裁和题材进行有侧重点的备考复习。 篇章阅读理解(单项选择) 本题型要求考生在阅读完一篇300~350个单词左右的文章后解答5个以单项选择题形式进行考查的题目。其所考查的内容一般不会是从文章能直接找到答案的，而需要考生运用自己的语言知识、逻辑知识等进行推敲和加深理解。这种题型可以考查任何层次、全局性、细节性的内容。虽然提供4个答案供考生进行选择，但干扰项大多具有迷惑性，这就要求考生对所读文章内容达到真正的理解。 1、解题步骤 第一步，读问题，划出标志词或关键词 快速浏览题目，对5个题目有大概印象以便阅读时有侧重点。一般来说，对于本身已经明确其考查内容的题目，标志词和关键词是比较容易找到的，只看一下题干即可，而对于那些并没有出现标志词和关键词的题目，如：The author suggests that，可以在解答试题时浏览选项作出解答。 第二步，略读文章 在略读中，首先阅读第一段，因为第一段通常会告诉我们作者将要讨论的话题。然后再阅读最后一段，以帮助我们对文章内容进行概
Passage 1 There are some very good things about open education. This way of teaching allows the students to grow as people develop their own interests in many subjects. Open education allows students to be responsible for their own education, as they are responsible for what they do in life. Some students do badly in a traditional classroom. The open classroom may allow them to enjoy learning. Some students will be happier in an open education school. They will not have to worry about grades or rules. For students who worry about these things a lot, it is a good idea to be in an open classroom. But many students will not do well in an open classroom. For some students, there are too few rules. These students will do little in school. They will not make good use of open education. Because open education is so different from traditional education, these students may have a problem getting used to making so many choices. For many students it is important to have some rules in the classroom. They worry about the rules even when there are no rules. Even a few rules will help this kind of student. The last point about open education is that some traditional teachers do not like it. Many teachers do not believe in open education. Teachers who want to have an open classroom may have many problems at their schools. You now know what open education is. Some of its good points and bad points have been explained. You may have your own opinion about open education. The writer thinks that open education is a good idea, but only in theory. In actual fact, it may not work very well in a real class or school. The writer believes that most students, but of course not all students, want some structure in their classes. They want to have rules. In some cases, they must be made to study some subjects. Many students are pleased to find subjects they have to study interesting. They would not study those subjects if they did not have to. 1.Open education allows the students to ____. A.grow as the educated B.be responsible for their future C.develop their own interests D.discover subjects outside class 2. Open education may be a good idea for the students who ____. A.enjoy learning B.worry about grades C.do well in a traditional classroom D.are responsible for what they do in life 3. Some students will do little in an open classroom because ____. A.there are too few rules B.they hate activities C.open education is similar to the traditional education D.they worry about the rules 4. Which of the following is NOT mentioned in the passage?____ A.Some traditional teachers do not like it.
《分析化学》阅读材料03 摘自Analytical Chemistry (FECS) ●In the Br?sted-Lowry theory, an acid is a proton donor and a base is a proton acceptor. Each acid is related to its conjugate base and vice versa: Acid = base + proton Therefore, the conjugate base of a strong acid must be a weak base and the conjugate base of a weak acid must be a strong base. Together they form a couple, and an acid without its conjugate base is a meaningless concept. In order to release a proton, the acid must find a base to accept it. In an aqueous solution, the proton, H+, having an extremely small ionic radius, cannot exist as such. It is hydrated, forming the hydronium ion H3O+ and higher hydrates. Thus, an acid-base equilibrium is not a simple dissociation equilibrium, but the result of a proton transfer reaction in which there are at least two reagents and two products. Such a process is also called protolysis. The overall reaction is expressed by: HX + H2O = H3O+ + X-. The overall equilibrium constant is K = [H3O+][X-]/[HX][H2O]. The acid dissociation constant Ka is given by: Ka = K[H2O] = [H3O+][X-]/[HX]. Ka reflects not only the acid strength of HX, but also the base strength of water. This why different acid dissociation constants are observed for the same acid in different solvent. ●Similar proton transfer reactions exist in all solvents possessing proton donor and acceptor properties. Proton transfer reactions are extremely fast. This makes them very suitable for analytical applications and acid-base reactions have found wide use in volumetric methods and other analytical techniques. ●The pH value is a measure for the acidity or basicity of a solution, aqueous or nonaqueous. ●Acid-base indicators are chemical substances with acid-base properties, having different colors in their protonated and deprotonated forms. ● A most important application of acid-base systems is related to the property of such a system to act as a buffer. Many chemical reactions produce protons (in aqueous solutions hydroniums) or hydroxide ions. If these products remain in the system, a corresponding pH change is observed. However, if a buffer is present in the solution it reacts with the liberated hydrogen or hydroxide ions so that only a relative small change of pH occurs. Buffer consist of a mixture of a weak acid and its conjugate base. The most efficient buffer for a given pH consists of a 1:1 ratio of the protonated and deprotonated forms of a weak acid (with pKa = pH). This cannot always be achieved, but if we wish to prepare a solution of a certain pH, we select a weak acid with a pKa value close to the desired pH. Buffer solution resists changes in pH upon adding of strong acids or strong bases. Depending on the relative concentrations of the acid and base forms of the buffer, the system can resist small or large additions of strong acid or base. This buffer capacity is defined as the number of moles of strong acid of base required to change the pH of 1 L of buffer solution by one pH unit. Solutions with high or low pH values, formed as a result of dissolution of large quantities of a strong base or acid, are characterized by a large buffer capacity, although the electrolyte practically consists of only one of the conjugate forms (e.g., HCl or NaOH solutions). ● A general requirement for all volumetric methods is that the titration process is fast and that it proceeds in a definite stoichiometric ratio, the endpoint of the reaction must by easy to detect and the reaction should be specific and not influenced by other constituents of the solution, i.e., there should be no interference. Question: 1. A H3PO4 solution is brought to pH = 7.00 by the addition of NaOH. Calculate the concentration of the various forms of orthophosphate if the total phosphate concentration in buffer is 0.200 mol /L. pKa1 = 2.16, pKa2 = 7.21, pKa3 = 12.32. 2. A buffer solution is prepared from acid, HA, Ka = 5 10-5, and its salt. The concentration of HA in the buffer is 0.25 mol / L. To 100 mL of the buffer added 5.0 mmol of NaOH, and the pH of the resulting solution is 5.60. What was the pH of the original buffer? 3.It is desired to change the pH of 100 mL of 0.100 mol / L HCl from 1.00 to 4.40 by the addition of sodium acetate, CH3COONa3H2O. How much solid sodium acetate salt must be added in grams? Assume no volume change for the solution as the result of the addition. 4.What is the buffer capacity of a solution which is 0.100 mol / L of NH3 and 0.200 of NH4Cl? 5.Calculate the pH of each of the following solution: (a) Water in equilibrium with CO2 of the air; pKa1 = 6.38, pKa2 = 10.25. (b) Water as in part (a) brought to pH = 7.00 with NaOH and allowed to regain equilibrium with CO2. 6. Derive the following expression for the pH at the first stoichiometric point in the titration of a mixture of two weak acid: HA, the stronger, Ka1, concentration C1; HB, the weaker, Ka2, concentration C2: pH = 1/2 (pKa1 + pKa2) – 1/2 lg (C1/C2)
最新中考英语阅读理解练习题 一、初三英语阅读理解（含答案详细解析） 1．阅读理解 Radio and television are very popular in the world today. Millions of people watch TV. Perhaps more people listen to the radio. The TV, of course, is more useful than the radio. On TV you can see and hear what is happening in the world. Now the radio is not disappearing. It's still with us. And the number of listeners is becoming larger. One reason for this is the invention of the transistor（晶体管）radio. The transistor radio is sometimes very small. It is very easy to carry. You can put one in your pocket and listen to it on the bus when you go to work. It is better for blind people. Many old people don't have good sight （视力）to watch TV. When people are working，they can't watch TV but they can listen to music or news over the radio. What's more，the radio is much cheaper than the TV. （1）After the television was invented，people ____. A. think it is unnecessary to use the radio B. don't want to use the radio any more C. are still using the radio D. find the radio is disappearing （2）One of the reasons for the larger number of listeners of the radio is that ____. A. the TV was invented B. the transistor radio was invented C. people don't like watching TV D. millions of people watch TV （3）____ listen to the radio more because their sight isn't good enough. A. Children B. Young people C. Old people D. Adults （4）Usually ____ can be used easily while people are moving or working. A. the radio B. the TV C. both the TV and the radio D. neither the radio nor the TV 【答案】（1）C （2）B （3）C （4）A 【解析】【分析】大意：本文讲述收音机和电视机在世界上的很受欢迎，电视与收音机比，电视更有用，然而收音机由于体积小便宜，便于携带，听众也越来越多，深受老年人喜爱。 （1）细节题。根据Perhaps more people listen to the radio.可知，电视发明后，人们依然使用收音机，故选C。 （2）细节题。根据One reason for this is the invention of the transistor（晶体管）radio. 可知，收音机听众的数量更多其中一个原因是晶体管收音机被发明，故选B。 （3）推断题。根据 Many old people don't have good sight（视力）to watch TV.可知，老年人由于视力不好听广播的人更多，故选C。 （4）细节题。根据When people are working，they can't watch TV but they can listen to music or news over the radio.可知，通常人们移动或者工作时可以听收音机，故选A。 【点评】考查阅读理解。细节题和推断题是阅读理解题中常考题型。细节题需要从文中寻
2020年高三英语材料之阅读理解精品版
高三英语材料之阅读理解 阅读理解1 A Besides entertainment and beautiful lanterns, another important part of the Lantern Festival ,or Yuanxiao Festival is eating small dumpling balls made of glutinous rice flour. We call these balls Yuanxiao or Tangyuan. Obviously, they get the name from the festival itself. It is said that the custom of eating Yuanxiao originated during the Eastern Jin Dynasty in the fourth century, then became popular during the Tang and Song periods. The fillings inside the dumplings or Yuansiao are either sweet or salty. Sweet fillings are made of sugar, Walnuts, sesame（芝麻）, osmanthus flowers(桂花), rose petals, sweetened tangerine（橘子）peel, bean paste, or jujube paste（枣子酱）. A single ingredient or any combination can be used as the filling . The salty variety is filled with minced meat（肉末儿）, vegetables or a mixture. The way to make Yuanxiao also varies between northern and southern China. The usual method followed in southern provinces is to shape the dough of rice flour into balls, make a hole, insert the filling, then close the hole and smooth out the dumpling by rolling it between your hands. In North China, sweet or nutmeat stuffing is the usual ingredient. The fillings are pressed into hardened cores, dipped lightly in water and rolled in a flat basket containing dry glutinous rice flour. A layer of the flour sticks to the filling, which is then again dipped in water and rolled a second time in the rice flour. And so it goes, like rolling a snowball, until the dumpling is the desired size. The custom of eating Yuanxiao dumplings remains. This tradition encourages both old and new stores to promote their Yuanxiao products. They all try their best to improve the taste and quality of the dumplings to attract more customers. 1.Which of the following is NOT true? A．The custom of eating Yuanxiao dates back to the fourth century. B．Sugar, rose petals and minced meat are all fillings of Yuanxiao. C．Sweet Yuanxiao are usually made in southern China. D．People in northern China usually make Yuanxiao by rolling like a snowball. 2.Which country does the Lantern Festival come from? A．China B．South Korea C．Jin Dynasty D．Tang and Song periods. 3.Choose the right order of making Tangyuan in southern provinces. ① make a hole and insert the filling ② roll the dough between your hands ③ shape the dough of rice flour into balls ④ close the hole ⑤ prepare some rice flour A．⑤③②①④ B．③⑤①②④ C．③①④②⑤ D．⑤③①④② 4.What is the best title of this passage? A．The Lantern Festival
最牛英语口语培训模式：躺在家里练口语，全程外教一对一，三个月畅谈无阻！ 洛基英语，免费体验全部在线一对一课程：https://www.doczj.com/doc/0c17648768.html,/wenkxd.htm（报名网址）Passage 14 Attention to detail is something everyone can and should do-especially in a tight job market. Bob Crossley, a human-resources expert notices this in the job applications that come cross his desk every day. “It’s amazing how many candidates eliminate themselves,”he says. “Resumes arrive with stains. Some candidates don’t bother to spell the company’s name correctly. Once I see a mistake, I eliminate the candidate, ”Crossley concludes. If they cannot take of these details. “Why should we trust them with a job?” Can we pay too much attention to detail? Perfectionists struggle over little things at the cost of something larger they work toward. “To keep from losing the forest for the trees,”says Charles Garfield, associate professor at the University of California, San Francisco, “we must constantly ask ourselves how the details we’re working on fit into the larger picture they don’t, we should drop them and move to something else.” Garfield compares this process to his work as a computer scientist at NASA. “The Apollo II moon launch was slightly off-course 90 percent of the time,”says Garfield. “But a successful landing was still likely because we knew the exact coordinates of our goal. This allowed us to landing was still likely because we knew the exact coordinates of our goal. This allowed us to make adjustments as necessary.”Knowing where we want to go helps us judge the importance of every task we undertake. Too often we believe what accounts for other’s success is some special secret or a lucky break. But rarely is success so mysterious. Again and again, we see that by doing little things within our grasp well, large rewards follow. 66. According to the passage, some job applicants were rejected________ A) because of their carelessness as shown in their failure to present a clean copy of a resume B) because of their inadequate education as shown in their poor spelling in writing a resume C) because they failed to give a detailed description of their background in their applications D) because they eliminated their names from the applicants list themselves 67. The word “perfectionists”(Line 1, Para 3)refers to those who________ A) demand others to get everything absolutely right B) know how to adjust their goals according to the circumstances C) pay too much attention to details only to lose their major objectives D) are capable of achieving perfect results in whatever they do 68. Which of the following is the author’s advice to the reader? A) Although too much attention to details may be costly, they should not be overlooked B) Don’t forget details when drawing pictures
计算机专业英语阅读材料 计算机英语（1） Desktop Pattern In the graphical user interface of Microsoft Windows 98,a graphical pattern-called wallpaper-displayed on the desktop (the background "beneath" windows, icons, and dialog boxes). The pattern or picture in the screen background that can be chosen by the user. To change the desktop pattern, choose Display from the Control Panel. 桌面图案 在Microsoft Windows 98的图形用户界面中,一种显示在桌面上称为壁纸(Wallpaper )的图形图案(窗口、图标和对话框后面的背景),屏幕背景可由用户选择图案样式或画面。要改变桌面图案时,从控制面板上选择显示方式。 计算机英语（2） Federated Database In scientific networking ,a collaborative database (part of a collaborator) in which scientists pool their knowledge and discoveries .Federated databases are one proposed solution to the Grand Challenges——problems that are so complex that they far outstrip the capabilities of individual scientists ,or even individual research institutions ,to tackle them independently. 联合式数据库 在科学联网中,科学家们汇集其知识和发现的一种合作数据库(合作的一部分)。联合数据库是对种种重大挑战问题(Grand Challenges)的一种建议性的解决方案——这些问题太复杂,以致于超出单个科学家的能力,甚至单个研究所都无法来单独解决它们。 计算机英语（3） Collapse When creating an outline or viewing a directory tree (such as in the Windows Explorer ),the process of hiding all the outline levels or subdirectories below the selected outline heading or directory. 折叠 当生成一个题纲或观察一个目录树(如在Windows资源管理器中)时,在选定的题纲标题或目录下隐藏所有的题纲层或子目录的过程。 计算机英语（4） Collision In local area networks (LANs) ,a garbled transmission that results when two or more workstations transmit to the same network cable at exactly the same time . Networks have means of preventing collisions. 冲突 在局域网(LANs)中,当两个或多个工作站恰好在同时向同一个网络线路上传送(数据)时产生的错乱传输。网络拥