Giáo trình Tiếng Anh trong kỹ thuật hóa học: Phần 1

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Cuốn giáo trình "Tiếng Anh trong kỹ thuật hóa học" được biên soạn nhằm bổ sung cho sinh viên các từ vựng, tổ hợp từ, thuật ngữ, cấu trúc ngữ pháp hay gặp trong những tài liệu khoa học kỹ thuật, giúp sinh viên làm quen với việc dịch Anh-Việt và ngược lại, viết một văn bản khoa học bằng tiếng Anh. Sách được chia thành 2 phần, mời các bạn cùng tham khảo phần 1 cuốn sách.

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Nội dung Text: Giáo trình Tiếng Anh trong kỹ thuật hóa học: Phần 1

PGS.TS. BÙI THỊ LỆ THỦY PGS.TS. BÙI THỊ LỆ THỦY PGS.TS. BÙI THỊ LỆ THỦY GIÁO TRÌNH GIÁO TRÌNH GIÁO TRÌNH TIẾNG ANH TRONG KỸ THUẬT HÓA HỌC TRONG KỸ THUẬT HÓA HỌC TRONG KỸ THUẬT HÓA HỌC ISBN: 978-604-76-1983-2 32 Giá: 50.000 đ
PGS.TS. BÙI THỊ LỆ THỦY GIÁO TRÌNH TIẾNG ANH TRONG KỸ THUẬT HÓA HỌC NHÀ XUẤT BẢN GIAO THÔNG VẬN TẢI HÀ NỘI - 2019
CONTENTS LỜI NÓI ĐẦU ................................................................................................................ 1 PART 1 THE BASIC UNITS......................................................................................... 6 I.1 TYPICAL UNITS............................................................................................. 7 UNIT 1 SOME CONCEPTS IN CHEMISTRY ........................................................ 7 UNIT 2 HYDROCARBONS ................................................................................... 10 UNIT 3 CHEMICAL KINETIC AND CATALYSIS.............................................. 14 UNIT 4 ANALYTICAL CHEMISTRY .................................................................. 16 UNIT 5 CHEMICAL THERMODYNAMICS ........................................................ 19 UNIT 6 EMULSIONS ............................................................................................. 23 UNIT 7 PLASTICS IN THE CHEMICAL AGE..................................................... 27 UNIT 8 ENZYMES ................................................................................................. 31 I.2 ADDITIONAL UNITS .................................................................................. 34 UNIT 9 PROPERTIES OF GELS............................................................................ 34 UNIT 10 SOLVENT PROPERTIES OF SURFACTANT SOLUTIONS. EMULTION POLYMERIZATION......................................................................... 37 UNIT 11 THE NATURE OF RUBBER - LIKE ELASTICITY ............................. 39 UNIT 12 THERMOPLASTIC ELASTOMERS. THERMOSETTING AND THERMOPLASTIC MATERIAL ........................................................................... 42 UNIT 13 THERMOPLASTIC ELASTOMERS ...................................................... 45 UNIT 14 ABS PLASTIC ......................................................................................... 49 UNIT 15 HAFNIUM ................................................................................................ 52 REFERENCES ............................................................................................................. 56 PART 2 THE CHEMICAL ENGINEERING UNITS ................................................. 57 UNIT 16 TYPES OF REACTORS .......................................................................... 58 UNIT 17 HEAT TRANSFER AND ITS APPLICATIONS .................................... 62 UNIT 18 EXTRACTION WITH SOLVENTS ........................................................ 67 UNIT 19 INTRODUCTION TO DISTILLATION AND ATMOSPHERIC DISTILATION ......................................................................................................... 72 UNIT 20 VACUUM DISTILLATION .................................................................... 77 3
UNIT 21 STEAM DISTILLATION ......................................................................... 81 UNIT 22 CRYSTALLIZATION .............................................................................. 86 UNIT 23 ADSORPTION .......................................................................................... 90 UNIT 24 EVAPORATION....................................................................................... 93 UNIT 25 CHROMATOGRAPHY ............................................................................ 97 UNIT 26 LIQUIS-SOLID CHROMATOGHRAPHY ........................................... 100 REFERENCES ............................................................................................................ 104 PART 3 THE PETROCHEMICAL INDUSTRY AND REFINERY UNITS ............ 105 III.1 TYPICAL UNITS ....................................................................................... 106 UNIT 27 ON OIL AND GAS INDUSTRY ............................................................ 106 UNIT 28 COMPOSITION OF PETROLEUM ...................................................... 108 UNIT 29 BASIC PHYSICO-CHEMICAL PROPERTIES OF PETROLEUM AND PETROLEUM PRODUCTS ................................................................................... 112 UNIT 30 BASIC PHYSICO-CHEMICAL PROPERTIES OF PETROLEUM AND PETROLEUM PRODUCTS (CONTINUED) ........................................................ 117 UNIT 31 DISTILLATION OF PETROLEUM ...................................................... 121 UNIT 32 THERMAL PROCESSES IN REFINERY ............................................. 126 THERMAL CRACKING ....................................................................................... 126 UNIT 33 CATALYTIC PROCESSES IN REFINERY ......................................... 131 III.2 ADDITIONAL UNITS ............................................................................... 136 UNIT 34 CATALYTIC CRACKING OF PETROLEUM ..................................... 136 UNIT 35 CATALYTIC REFORMING OF PETROLEUM................................... 142 REFERENCES ............................................................................................................ 147 PART 4 ACADEMIC WRITING ............................................................................... 148 UNIT 36 INTRODUCTION TO ACADEMIC WRITING .................................... 149 UNIT 37 TYPES AND STRUCTURE OF ACADEMIC WRITING .................... 153 UNIT 38 HOW TO WRITE A SUCCESSFUL...................................................... 157 SCIENTIFIC MANUSCRIPT ................................................................................ 157 REFERENCES ............................................................................................................ 161 4
LỜI NÓI ĐẦU Giáo trình này được biên soạn cho những sinh viên năm cuối của ngành Kỹ thuật Hoá học. Giáo trình nhằm bổ sung cho sinh viên các từ vựng, tổ hợp từ, thuật ngữ, cấu trúc ngữ pháp hay gặp trong những tài liệu khoa học kỹ thuật, giúp sinh viên làm quen với việc dịch Anh-Việt và ngược lại, viết một văn bản khoa học bằng tiếng Anh. Nội dung của giáo trình gồm 4 phần. Các bài học trong các phần được biên soạn tăng dần theo mức độ chuyên sâu trong lĩnh vực hoá học. Trong phần một tác giả chọn các bài khoá liên quan đến những kiến thức cơ bản của Hoá học, những chuyên đề cơ bản của Hoá học. Mỗi bài khoá đều sắp xếp theo trật tự logic từ bài đọc hiểu, các bài tập để sinh viên ôn luyện, từ đó giúp sinh viên làm quen với những từ, tổ hợp từ và tập trung vào kỹ năng đọc hiểu, dịch từ tiếng Anh sang tiếng Việt và ngược lại. Phần hai gồm những bài khoá liên quan đến lĩnh vực Kỹ thuật Hoá học như lò phản ứng, những kỹ thuật tách chất phổ biến và thông dụng nhất. Cấu trúc bài khoá ở phần này cũng tương tự như ở phần một. Các bài tập đi kèm làm cho bài khoá thêm sinh động và đưa vào những cấu trúc ngữ pháp hay gặp trong khoa học. Phần ba là những bài khoá tập trung vào lĩnh vực Hoá dầu. Nội dung mỗi bài đều gắn với chuyên môn sâu của sinh viên. Sau mỗi bài đều có bài tập để sinh viên rèn luyện khả năng đọc, dịch và viết tiếng Anh. Trong phần cuối cùng tác giả biên soạn ba bài cơ bản về kỹ thuật viết một văn bản khoa học trong lĩnh vực Kỹ thuật Hoá học, giúp sinh viên nắm được những bước cơ bản và sườn của một bản thảo bài báo khoa học. Tác giả xin trân trọng cảm ơn các đồng nghiệp đã đóng góp ý kiến để hoàn thành cuốn sách này. Xin chân thành cảm ơn sự quan tâm của độc giả và mong nhận được những ý kiến góp của các độc giả và các bạn đồng nghiệp để cuốn sách ngày một hoàn thiện hơn. Tác giả 5
PART 1 THE BASIC UNITS 6
I.1 TYPICAL UNITS UNIT 1 SOME CONCEPTS IN CHEMISTRY Structure of Atoms. According to Dalton’s atomic theory, a chemical element is material composed of only one type of atom. Atoms are very small particles that cannot be separated into simpler substances and that singly or in combination constitute all matter. All atoms are constructed from the three particles: the electron, proton, and neutron. Both neutrons and protons occupy the nucleus, which is in the center of the atom. The electrons orbit around the nucleus. Each atom contains equal number of electrons and protons, therefore, atoms are neutral. An atom of one element is distinguished from an atom of another element by its number of protons. The number of proton in the atomic nucleus is called the atomic number Z of an element. For instance, carbon atoms contain six protons and six electrons; therefore, the atomic number of carbon is 6. The total mass of an atom is almost entirely by the number of protons and neutrons because the mass of electrons is so much smaller. The atoms of almost element have the same proton number but different neutron number; therefore they have different mass number. These atoms are called isotopes. For example, helium exists as helium-3 or He-3 (its nucleus contains 2 protons but only 1 neutron) or as helium-4 or He-4 (2 protons and 2 neutrons). These two examples are called isotopes of helium. The elements are arranged in the periodic table, the invention of which is generally attributed to the 19th century Russian chemist Dimini Mendeleev. In the standard periodic table, the elements are listed in order of increasing atomic number (the number of protons in the nucleus of an atom). A new row (period) is started when a new electron shell has its first electron. Elements containing the same number of electron layers are arranged in the same period while elements with the same number of electrons in a particular subshell fall into the same columns. Molecules, substances, and chemical compounds. Molecules are composed of the atoms of one or more elements. Nitrogen exists as nitrogen molecules in atmosphere, each molecule contains two nitrogen atoms. Its symbolic representation is N2. Water molecule contains one oxygen atom and two hydrogen atoms. Compounds are composed of the atoms of one or more elements. N2 is an elementary substance and water is a compound but both of them are called substances. Exercises 1.1 Read and translate into Vietnamese Concept, structure, atom, atomic, theory, element, material, compose, substance, particle, combination, constitute, matter, electron, proton, neutron, neutral, nucleus, orbit, distinguish, atomic number, mass number, helium, arrange, periodic table, attribute, electron shell, subshell, molecule, substance, elementary substance, compound. 7
1.2 Answer the following questions 1. What is an element? 2. What is an atom? 3. How many kinds of particles are there in every atom? What are they? 4. What is the atomic number of an element? 5. How can we determine the mass of an atom? 6. What is a molecule? 7. Please distinguish an elementary substance and a compound. 1.3 Translate into Vietnamese paying attention to the words in bold type 1. The name ABS, based on the first letters of each of the monomeric components has been adopted for this family. 2. By introducing acrylonitrile monomer into a similar system, a significant improvement in all these properties is obtained, as well as outstanding toughness and resistance. 3. Various combinations of properties are possible, thus making these polymers most attractive for a larger number of current and newly developed applications. 4. ABS plastics are extremely useful and versatile, since ease of processing and forming allows them to be used for a great number of applications. 5. The strength of a fabricated item produced from ABS plastic is dependent on a number of variables. 1.4 Translate into English 1. Nguyên tử là phần tử nhỏ nhất của vật chất có thể tồn tại độc lập. 2. Nguyên tử được cấu tạo từ proton, electron và nơtron. Electron tích điện âm, ptoton tích điện dương còn nơtron không mang điện. 3. Trong một nguyên tử, số proton bằng với số electron nên nguyên tử luôn trung hòa về điện. 4. Vì khối lượng của eletron rất nhỏ so với khối lượng của nơtron và proton nên khối lượng nguyên tử được tính xấp xỉ là tổng khối lượng của proton và nơtron. 5. Phân tử chứa các nguyên tử của một hoặc nhiều nguyên tố. 6. Các hợp chất bao gồm các nguyên tử của hai hay nhiều nguyên tố. 7. Các hạt proton và neutron nằm ở trung tâm và tạo ra hạt nhân còn các electron chuyển động xung quanh hạt nhân tạo ra các lớp electron. 8. Đồng vị là các nguyên tử của cùng nguyên tố có số nơtron khác nhau. 8
9. Các nguyên tố trong cùng một chu kỳ có cùng số lớp electron 10. Các nguyên tố trong cùng một nhóm có cùng số electron ở lớp ngoài cùng, do đó, chúng có tính chất tương tự nhau. 11. Các nguyên tố hóa học được sắp xếp vào bảng hệ thông tuần hoàn dựa vào cấu hình electron của chúng. 1.5 Write a short summary of the text 9
UNIT 2 HYDROCARBONS Hydrocarbons are compounds containing only carbon and hydrogen atoms. 1. Paraffin hydrocarbons (alkanes) Their general formula is CnH2n+2, where n is the number of carbon atoms. Each next hydrocarbon can be obtained from the previous one by substituting a methyl group CH3 for the extreme hydrogen atom in the chain: CH4 C2H6 C3H8 C4H10 methane ethane propane butane The paraffin hydrocarbons are the most stable of the lot because all valence bonds are fully satisfied as indicated by the single linkage. Most reactions involve the replacement of hydrogen atoms with other atoms, the carbon linkage remains stable. Under common conditions, the hydrocarbons from CH4 to C4H10 are gaseous, those from C5H12 to C15H32 are liquids (they enter the composition of gasoline, kerosene, and diesel- fuel fractions), and those from C16H34 are solid (paraffins). Beginning from the fourth term in the series (butane C4H10), hydrocarbons may exist in two or more forms differing in the structure. For instance, butane may exist in two forms: n-butane and isobutane. Compounds which have the same chemical formula but different molecular structure are called isomers. The number of isomers increases for each next hydrocarbon in the series. Hydrocarbons of the formula C13H28 may have 802 isomers, those of the formula C14H30, 1858, and so on. Thus, the composition of petroleum is quite complicated. Isomers possess different physical and chemical properties. For instance, heptane of normal structure (n- C7H16) has an octane number of zero, whereas isooctane (iso- C8H18) has an octane number of 100. 2. Naphthenic Hydrocarbons (Cycloalkanes) Their general formula is CnH2n. They were discovered by V.V. Markovnikov, a prominent Russian chemist, when studying petroleum of Caucasian deposits. In their chemical properties; naphthenic hydrocarbons are similar to paraffins, but differ from the latter in having a cyclic structure. Cyclopentane and cyclohexane derivatives are especially important for the quality of petroleum and petroleum products. 3. Benzene Hydrocarbons (Arenes) Arenes of the benzene series have the general formula CnH2n-6. The cyclic structure of arenes differs from that of naphthenes by the presence of double bonds on the aromatic ring. If one or more atoms of hydrogen in the ring are replaced by a methyl (-CH3) or an ethyl (- C2H5) group, other arenes (toluene, xylenes and ethylbezene) are formed. Arenes are valuable raw materials for chemical technology and the manufacture of antiknock gasoline. 10
4. Unsaturated Hydrocarbons (Olefins) Hydrocarbons of the ethylene series have the general formula is CnH2n, are characterized by a double bond in the molecule (ethylene C2H4, propylene C3H6, butylenes C4H8, amylenes C5H10, etc.) and may be of either normal or isomeric structure. They are not present in crude petroleum, but constitute an appreciable part of the products obtained in thermal and some catalytic processes of petroleum processing. These hydrocarbons have high reactivity and are used for the manufacture of some important products, such as polyethylene, polypropylene, ethylene and propylene oxides and their derivatives. Along with olefins, some less saturated hydrocarbons, with two double bonds in the structure, such as diolefins, can form in petroleum processing. These are extremely unstable and for that reason should not be present in final petroleum products. Some of them (butadiene C4H6 and isoprene C5H8) are obtained intentionally from petroleum and used for the manufacture of synthetic rubber and like products. Exercises 2.1 Read and translate into Vietnamese Paraffin, general formula, substitute, methane, ethane, propane, butane, stable, satisfy, linkage, single, double, triple, bond, gasoline, kerosene, gaseous, fuel, petroleum, diesel, fraction, solid, isomer, isomeric, heptane, isooctane, naphthene, naphthenic, cycloalkane, prominent, cyclopentane, cyclohexane, derivatives, arene, benzene, aromatic, toluene, xylene, ethylbenzene, antiknock, unsaturated, ethylene, acetylene, amylene, butylene, constitute, appreciable, petroleum processing, polyethylene, polypropylene, propylene oxides, diolefin, unstable, butadiene, synthesis, synthesize, synthetic, rubber. 2.2 Answer the following questions 1. What kinds of substances are hydrocarbons? 2. What is the general formula of alkanes? 3. What are isomers? 4. What can you say about the properties of isomers? 5. Which compounds are called cyclic compounds? 6. What are benzene hydrocarbons or arene? 7. What are the uses of benzene and benzene hydrocarbons? 8. What are properties of unsaturated hydrocarbons? 9. What are the uses of unsaturated hydrocarbon? 11
2.3 Fill the following schemes with suitable expressions Funnel, filter paper, mixture, residue, glass rod, filtrate, beaker, and stand. 8 8 Figure 1. Laboratory setup for filtration experiment 2.4 State the purpose of the system and describe its operation Figure 2. Laboratory setup for vacuum filtration experiment Moisten the filter paper with the solvent used in the crystallization process and apply suction before the filtration is started. The suspension of crystals is then poured onto the filter in such a way that a layer of uniform thickness is collected. If crystals adhere to the walls of the flask in which crystallization was carried out, they may be washed out with some of the filtrate. 12
2.5 Fill the following schemes with suitable expressions Support stands, water in, water out, pot, thermometer, rubber tubing, adapter, receiver, thermometer adapter, condenser, clamp, boiling chips, distilling head, support ring, electric flask heater. Figure 3. Laboratory setup for simple distillation experiment 2.6 Translate into English 1. Hydrocacbon là các hợp chất chỉ chứa cacbon và hydro. 2. Trong dầu mỏ chỉ chứa các hydrocacbon paraffin, naphten và aromatic vì chúng bền. Các hydrocacbon không no chỉ tạo ra trong quá trình chế biến dầu mỏ. 3. Các hydrocacbon không no có hoạt tính vì chúng có các liên kết bội không bền. 4. Các paraffin và naphten có hoạt tính hoá học thấp do phân tử của chúng chỉ chứa các liên kết đơn (bão hoà). 2.7 Write a short summary of the text 13
UNIT 3 CHEMICAL KINETIC AND CATALYSIS Chemical kinetics, also known as reaction kinetics, is an important part of chemistry. Chemical kinetics study of how experimental conditions can influence the speed and yield of a chemical reaction. Investigation of chemical kinetics can give us the information about the reaction's mechanism as well as the mathematical models that can describe the characteristics of a chemical reaction. There are many factors that determine the rate of a reaction. Temperature is an important factor which affects the reaction. Almost the reactions need energy by raising the temperature. The higher temperature the higher the atoms, molecules, and ions move which leads to the frequency of collision increases. High frequency of collision helps the particle to overcome the activation barrier. High concentration of the reactants also increases the rate of a reaction. If the reactant molecules are closed the collisions become more frequent which makes the reaction more likely happens. In addition, the rate depends also upon physical form of reactant, the intimacy of their mixture, the pressure and solvents, the special physical circumstances such as irradiation with visible light, ultraviolet light, X-rays, neutrons, and the presence of other substances which affect the reaction but are not changed by it (catalysts). A catalyst can accelerate a chemical reaction because it let the reaction takes place by an alternative pathway with lower activation energy barrier. Catalyst reacts to form a temporary intermediate which then regenerates the original catalyst in a cyclic process. In the presence of a catalyst, less free energy is required to reach the transition state, but the total free energy from reactants to products does not change. Many kinds of catalysts are used up to now such as acid, base, transition metal, complex, enzyme… Depend on the state of the catalytic reaction system catalysts may be classified as either homogeneous or heterogeneous. The molecules of a homogeneous catalyst are dispersed in the same phase (usually gaseous or liquid) as the reactant molecules. The molecules of a heterogeneous catalyst are not in the same phase as the reactants, which are typically gases or liquids that are adsorbed onto the surface of the solid catalyst. Enzymes and other biocatalysts are often considered as a third category. The detailed mechanism of catalysis is complex. Kinetically, catalytic reactions are typical chemical reactions; i.e. the reaction rate depends on the frequency of contact of the reactants in the rate-determining step. Usually, the catalyst participates in this slowest step, and rates are limited by amount of catalyst and its "activity". Rate equation for a chemical reaction is an equation that shows the relationship between reaction rates and the concentrations or pressures of the reactants and constant parameters. Depending on the rate equation we can distinguish the zero order, first order, second order reactions and so on. 14
Exercises 3.1 Read and translate into Vietnamese Chemical kinetic, kinetic, kinetically, catalysis, catalyst, catalytic, mechanism, mathematical model, factor, frequency, collision, activation, reactant, intimacy, circumstance, irradiation, visible, light, ultraviolet light, X-rays, accelerate, alternative, pathway, regenerate, cyclic process, free energy, transition metal, homogeneous, heterogeneous, adsorb, rate determining step, rate equation, zero order. 3.2 Answer the following questions 1. What is catalysis? 2. What is a catalyst? 3. Compare the homogeneous and heterogeneous catalysts! 4. Which kinds of catalysts are there? 5. What is the role of a catalyst? 6. What are the inhibitors and poisons of a reaction? 7. What is the rate-determining step? 8. Do catalysts change during the reaction? 3.3 Translate the following sentences into Vietnamese 1. Lewis found water and air to be thermodynamically unstable with respect to the formation of nitric acid. 2. Metastable or unstable compounds can be treated by the methods of thermodynamics, provided that they have a lifetime sufficiently long for thermodynamic measurements to be made. 3. Scientists consider adsorption from solutions to be physical or chemical. 4. It is noteworthy that in the case of phosphate buffers, the increase of pH is accompanied by a drop of interface tension between the two phases. 3.4 Translate into English 1. Chất xúc tác là chất làm tăng tốc độ phản ứng nhưng bản thân nó không bị biến đổi sau phản ứng. 2. Vai trò của chất xúc tác là làm giảm năng lượng hoạt hóa của phản ứng. 3. Ở cùng điều kiện nhiệt độ và nồng độ chất phản ứng, khi năng lượng hoạt hóa của phản ứng giảm đi thì tốc độ phản ứng tăng lên. 4. Chất xúc tác thường tham gia vào giai đoạn quyết định tốc độ phản ứng hay là giai đoạn chậm chất của phản ứng. 3.5 Write a short summary of the text 15
UNIT 4 ANALYTICAL CHEMISTRY One should keep in mind that industrial analysis is not necessarily a routine, boring occupation. It can be frustrating at times but it can also be fascinating, instructive, humorous, and even exciting. It is usually pleasant if one dedicates himself to learning about what goes on in chemical systems. The key for enjoying analytical work lies in knowing that the results will be useful and important. Problem - solving in analytical chemistry An analytical chemist should know enough about existing methodologies to choose the best one for application to a given sample, perhaps modifying it if necessary to fit the particular situation, and that there is also an analytical science which seeks the improvement of analytical methodologies with regard to scientific problems. Nowadays, with more and more instrumental methods in vogue, the analysts and determinators are coming closer together. To be a good chemist one must first be a good analytical chemist. We can teach instrumental analysis in industry, but we should not teach basic chemistry. Mercury? Questions and answers Some of you may be interested in the question of mercury and its determination in the environment. This is a fascinating question with many aspects. It illustrates again the importance of analytical chemists looking at the whole picture. Swedish scientists had developed a gas chromatographic method for the determination of alkyl and aryl mercuric compounds extracted from fish with benzene and dilute hydrochloric acid. They were interested in those compounds because of their use as slimicides, but it turned out that regardless of what compound was used, the mercury found in fish was present as a monomethylmercuric ion. A number of questions about the behavior of mercury remain to be answered. Several theories have been proposed as to how mercury might have gone from inorganic form in water or bottom sediment, into a methylated form of a fish. One theory assumes anaerobic conversion in the mud to volatile dimethyl mercury which enters fish via the gills. Another assumes aerobic conversion to monomethyl mercury by bacteria, with subsequent transfer up to the food chain. Still another assumes that a fish itself can methylate mercury taken in either through the gills as elemental vapor, or via the stomach as inorganic ions, or in an adsorbed state in silt particles. Before all these questions can be answered, we need to develop highly sensitive methods for each individual form of mercury. At present the most sensitive methods can go down only to about 0.05-ppm inorganic mercury in water. At the conference on environmental mercury contamination in 1970 in Ann Arbor, Michigan, USA a number of sources from which mercury may enter the environment were mentioned. Among them were the burning of fossil fuels, use of mercurial compounds for fungicides in agricultural seed treatments, use of elemental mercury in the electrical industry for manufacture of batteries and mercury vapour lamps, use of mercuric catalysts, and the 16
disposal of domestic sewage sludges. It will be up to analytical chemists to evaluate all of the sources and to provide the data on which proper action can be based. This will be true not only for mercury, but also for all environmental contaminants. It is interesting that both Finish and Swedish chemists have found fairly high content in fish from certain lakes in northern parts of their countries, remote from any known source of pollution. Another interesting fact is that mercury will be found in the hair of a person who has been exposed to it. The average person has about one or two ppm in his hair or even more. Having analyzed sections of the hair of a long- haired person and having known its growth rate, one can approximate the time and intensity of exposure. Most of these analyses have been done by neutron activation, which is advantageous because very small samples can be employed. However, hair can be analyzed by the atomic absorbance method following the digestion procedure used for fish analysis. A 100-mg sample is sufficient for hair in the range of 1 to 10 ppm. Exercises 4.1 Read and translate into Vietnamese Analysis, analytical, routine, occupation, frustrating, fascinating, instructive, humourous, pleasant, dedicate, methodology, modify, particular, vogue, determination, determinator, instrument, instrumental, mercury, mecuric, environment, fascinating, aspect, illustrate, chromatographic, dilute, alkyl, aryl, extract, benzene, slimicide, regard, regardless, monomethylmercuric, sediment, methylate, anaerobic, mud, aerobic, gill, assume, inorganic, organic, volatile, dimethyl mercury, subsequent, transfer, chain, stomach, sensitive, silt, individual, contaminate, contamination, contaminant, mention, fossil fuel, fungicide, agriculture, agricultural, battery, disposal, domestic, sewage, sludge, evaluate, source, remote, pollution, approximate, expose, exposure, intensity, absorbance, digestion, sufficient. 4.2 Answer the following questions 1. What is the key for enjoying analytical work? 2. How is industrial analysis? 3. What should an analytical chemist know? 4. Which compounds of mercury are present in fish? 5. How has mercury transferred from inorganic form to methylated form? 4.3 Translate into Vietnamese paying attention to the finite and non- finite forms of the verb 1. Having developed a gas chromatographic method for the determination of alkyl and aryl compounds the Swedish scientists got interested in those compounds. 2. Swedish scientists developed a gas chromatographic method for the determination of alkyl and aryl mercuric compounds extracted from fish. 17
3. The chemists extracted fairly high mercury contents from fish. 4. The scientists found high mercury contents in fish from certain lakes, remote from any known source of pollution. 5. Mercury found in fish was present as a monomethylmercuric ion. 4.4 Translate into Vietnamese paying attention to the pronoun “one” 1. One should keep in mind that industrial analysis is not necessarily a boring occupation. 2. It is pleasant if one dedicates himself to learning about what goes on in chemical systems. 3. An analytical chemist should know enough about existing methodologies to choose the best one for application. 4. To be a good chemist one must be first of all a good analytical chemist. 4.5 Translate into Vietnamese paying attention to the Model Verbs + Perfect infinitive 1. It was realized that drying may have caused some denaturation, but whatever the change it should not have affected the amino acid composition of the proteins. 2. It goes without saying that any of the acid derivatives (amide, ester, etc.) might have been prepared either from benzoyl chloride or benzoic anhydride instead of from benzoic acid. 3. The mercaptans obtained could have been oxidized in alkaline solutions to disulfides. 4. Zincate solutions could have been prepared by dissolving ZnO in aqueous KOH. 4.6 Read the following model of a summary The article “The pains and pleasures of industrial analytical chemistry” discusses what an analytical chemist should know about existing methodologies and presents a gas chromatographic method for determination of alkyl and aryl mercuric compounds extracted from fish with benzene and dilute hydrochloric acid. The paper provides examples of fairly high mercury content in fish from certain lakes of Sweden and Finland, which are remote from any known source of pollution and of finding mercury in the hair of a person exposed to it. The article illustrates and describes the importance of an analytical chemist who should use the best methodology to a given sample modifying it to fit the particular situation. 18
UNIT 5 CHEMICAL THERMODYNAMICS The science of thermodynamics concerns the chemical and physical processes, which involve the interconversion of various forms of energy, and it is not confined to the relation between heat and mechanical energy. It is developed mathematically on the basis of a number of postulates, which have been supported by experiments. Although its application to chemical processes quite general, thermodynamics is not at all concerned with either the rate of a process or the mechanism of it. Thermodynamics is based on two fundamental laws, called the first and second laws of thermodynamics. The two laws of thermodynamics constitute one of the most powerful tools of physical chemistry. Of fundamental importance to thermodynamics is the concept of equilibrium state. Thermodynamic equilibrium in the true sense refers to a condition in which the properties of a system are absolutely unchanging with time so that, if the system is disturbed slightly in some way, it will return to essentially the same condition after the disturbing force is removed. This latter criterion may differentiate between a true state of equilibrium and a metastable one. If a metastable equilibrium is disturbed, as, for example, by introduction of a catalyst or by local heating, it may spontaneously undergo a drastic change to some new state. Consider a container filled with chlorine gas. Provided that the container is sealed and thermally insulated from its surroundings a state of true thermodynamic equilibrium will be established in which the temperature and pressure are uniform. If we disturb the system by shining a light on it, some of the chlorine molecules will absorb radiation and dissociate into atoms. When we turn off the light, the chlorine atoms recombine and the system, except for the addition of a small amount of energy from the light beam, returns to its original condition. By way of contrast, a mixture of hydrogen and chlorine is metastable. Although chlorine and hydrogen react with one another at room temperature, the rate is so slow as to be virtually undetectable. Hence the system seems to behave in just the same way as the pure chlorine system, in which uniform temperature and pressure are established. However, if we direct a beam of light through this mixture, it explodes, forming hydrogen chloride and evolving a large amount of heat. After being disturbed in this way, the system can not revert spontaneously to its original condition. In fact, the change, which does occur (the explosion), is a state of true thermodynamic equilibrium. Although thermodynamics cannot deal with the rate at which reactions occur, it does establish the direction in which reaction can proceed. Metastable or unstable compounds can be treated by the methods of thermodynamics, provided that they have a lifetime sufficiently long for thermodynamic measurements to be made. This requirement may vary, depending on the type of experiment, from a minute fraction of a second to hours, or even days. In this regard, one can make the distinction between substances, which exits by virtue of its thermodynamic stability, or by reason only of its slow rate of reaction or decomposition. There is a wide range in degree of inertness of unstable system. Diamond, on the one hand, is inert to the extent that there is no observable conversion (under ordinary conditions) 19