化学专业英语(修订版)翻译

01 THE ELEMENTS AND THE PERIODIC TABLE 01 元素和元素周期表 The number of protons in the nucleus of an atom is referred to as the atomic number, or proton number, Z. The number of electrons in an electrically neutral atom is also equal to the atomic number, Z. The total mass of an atom is determined very nearly by the total number of protons and neutrons in its nucleus. This total is called the mass number, A. The number of neutrons in an atom, the neutron number, is given by the quantity A-Z. 在一个原子核中的质子数量被称为原子序数，或质子数，Z。在一个电中性原子中的电子数量也等于原子序数，Z。一个原子的总质量被测定是非常接近于原子核中质子和中子的总数。这个总数被称为质量数，A。在一个原子中的中子数量等于A – Z的数量。 The term element refers to, a pure substance with atoms all of a single kind. To the chemist the "kind" of atom is specified by its atomic number, since this is the property that determines its chemical behavior. At present all the atoms from Z = 1 to Z = 107 are known; there are 107 chemical elements. Each chemical element has been given a name and a distinctive symbol. For most elements the symbol is simply the abbreviated form of the English name consisting of one or two letters, for example: 这个术语(指chemical element)也可以指由相同质子数的原子组成的纯化学物质。对化学家来说，这类原子通过原子数来说明，因为它的性质是决定其化学行为。目前，从Z = 1 到Z = 107的所有原子是知道的；有107种化学元素。每一种化学元素起了一个名字和独特的象征。对于大多数元素都仅仅是一个象征的英文名称缩写形式，由一个或两个字母组成，例如： oxygen==O nitrogen == N neon==Ne magnesium == Mg 氧= =O 氮 = = N氖= = Ne 镁= =Mg Some elements,which have been known for a long time,have symbols based on their Latin names, for example: 很久以来就已经知道一些元素，根据他们的拉丁名字符号命名，例如： iron==Fe(ferrum) copper==Cu(cuprum) lead==Pb(plumbum) 铁= =铁(铁) 铜= =铜(铜) 铅= =铅(铅) A complete listing of the elements may be found in Table 1. 一个完整的元素可以在表1中被发现。 Beginning in the late seventeenth century with the work of Robert Boyle, who proposed the presently accepted concept of an element, numerous investigations produced a considerable knowledge of the properties of elements and their compounds1. In 1869, D.Mendeleev and L. Meyer, working independently, proposed the periodic law. In modern form, the law states that the properties of the elements are periodic functions of their atomic numbers. In other words, when the elements are listed in order of increasing atomic number, elements having closely similar properties will fall at definite intervals along the list. Thus it is possible to arrange the list of elements in tabular form with elements having similar properties placed in vertical columns2. Such an arrangement is called a periodic. 早在十七世纪末期，罗伯特波义耳就开始了这项工作，他提出了现在公认的元素的概念，大量的研究使我们对元素及其化合物的性质有了相当的了解。在1869年，门捷列夫和迈耶，独立工作，提出了元素周期律。用现代方式，元素周期律阐述了元素的特性原子序数的周期性函数。换句话说，当按原子序数增加的顺序排列元素，具有相近特性的元素将沿着列表以一定的间隔下降。因此，将具有类似性质的元素排成纵列，从而把元素排成表格形式是有可能的。像这样的排列叫元素周期表。 Each horizontal row of elements constitutes a period. It should be noted that the lengths of the periods vary. There is a very short period containing only 2 elements, followed by two short periods of 8 elements each, and then two long periods of 18 elements each. The next period includes 32 elements, and the last period is apparently incomplete. With this arrangement, elements in the same vertical column have similar characteristics. These columns constitute the chemical families or groups. The groups headed by the members of the two 8-element periods are designated as main group elements, and the members of the other groups are called transition or inner transition elements. 每个水平排的元素构成一个周期。但应该注意的是，周期长度会发生改变。非常短的周期只包含二元素，后面跟着两个8个元素短周期，然后是两个由18个元素组成的长周期。下一个周期包括32个元素，最后一个周期明显是不完整的。按照这样的安排，在同一垂直栏的元素有相似的特点。这些垂直栏构成化学族。两个8个元素的周期组成的元素被认为是主族元素，其他族的元素被称为过渡元素。 In the periodic table, a heavy stepped line divides the elements into metals and nonmetals. Elements to the left of this line (with the exception of hydrogen) are metals, while those to the right are nonmetals. This division is for convenience only; elements bordering the line—the metalloids-have properties characteristic of - both metals and nonmetals. It may be seen that most of the elements, including all the transition and inner transition elements, are metals. 在元素周期表，阶梯线将元素分成金属和非金属元素等。阶梯线左边的元素(除氢)是金属，右边的是非金属元素等。这个分割仅为方便使用；元素分界线上的元素—准金属具有金属和非金属的特性。这可以看出，大部分的元素，包括所有的过渡和内在过渡元素，是金属。 Except for hydrogen, a gas, the elements of group IA make up the alkali metal family. They are very reactive metals, and they are never found in the elemental state in nature. However, their compounds are widespread. All the members of the alkali metal family, form ions having a charge of 1+ only. In contrast, the elements of group IB —copper, silver, and gold—are comparatively inert. They are similar to the alkali metals in that they exist as 1+ ions in many of their compounds. However, as is characteristic of most transition elements, they form ions having other charges as well. 除了氢气，IA由碱金属元素组成。他们是非常活泼的金属，在自然界中，它们从没有以元素态形式出现。然而，他们的化合物是广泛存在的。所有的碱金属离子仅有1+的电荷。相比之下，IB 铜，银和金是惰性的。在他们的许多化合物他们存在1+离子，这与碱金属离子是相似的。然而，像许多过渡元素所具有的特点一样，他们也形成具有其他电荷的离子。 The elements of group IIA are known as the alkaline earth metals. Their characteristic ionic charge is 2+. These metals, particularly the last two members of the group, are almost as reactive as the alkali metals. The group IIB elements—zinc, cadmium, and mercury are less reactive than are those of group II A5, but are more reactive than the neighboring elements of group IB. The characteristic charge on their ions is also 2+. IIA的元素被称为碱土金属。其特点是离子电荷2+。这些金属，特别是最后两个元素，几乎具有与碱金属一样的反应活性。IIB元素，锌，镉，汞比IIA的元素具有更少的反应活性，但是比相邻的IB的元素有更强的反应活性。IB的元素离子的特征电荷也是2+。 With the exception of boron, group IIIA elements are also fairly reactive metals. Aluminum appears to be inert toward reaction with air, but this behavior stems from the fact that the metal forms a thin, invisible film of aluminum oxide on the surface, which protects the bulk of the metal from further oxidation. The metals of group IIIA form ions of 3+ charge. Group IIIB consists of the metals scandium, yttrium, lanthanum, and actinium. 除了硼、IIIA元素也是具有相当强活性金属。在空气中铝似乎惰性的，但这种行为的根源是金属表面形成了一层薄的、不可见的氧化铝膜，这层膜保护大量的金属的进一步氧化。IIIA金属离子具有3+的电荷。IIIA由金属钪，钇，镧系和锕系元素组成。 Group IVA consists of a nonmetal, carbon, two metalloids, silicon and germanium, and two metals, tin and lead. Each of these elements forms some compounds with formulas which indicate that four other atoms are present per group IVA atom, as, for example, carbon tetrachloride, CCl4. The group IVB metals —titanium, zirconium, and hafnium —also forms compounds in which each group IVB atom is combined with four other atoms; these compounds are nonelectrolytes when pure. IVA元素由一个非金属，碳、两个准金属，硅和锗，和两个金属，锡和铅组成。按照配位规则，这些元素的每一种形成一些化学物，这表明每一个IVA原子需要四个其他原子配位，例如，四氯化碳CCl4。IVB金属—钛、锆、和铪—也形成化合物，其中每个IVB原子结合四个其他原子；这些化合物的纯物质是非电解质。 The elements of group V A include three nonmetals — nitrogen, phosphorus, and arsenic—and two metals — antimony and bismuth. Although compounds with the formulas N2O5, PCl5, and AsCl5 exist, none of them is ionic. These elements do form compounds-nitrides, phosphides, and arsenides — in which ions having charges of minus three occur. The elements of group VB are all metals. These elements form such a variety of different compounds that their characteristics are not easily generalized. VA元素包括三种非金属--氮、磷、砷，和两种金属锑和铋。尽管物质N2O5，PCl5，AsCl5存在，但是其中没有一个是离子。这些元素能形成化合物—氮化物，磷化物，和砷化物—其中离子带3-价的负电荷。VB的元素都是金属。这些元素形成各种不同的化合物，它们的特性不容易归纳。 With the exception of polonium, the elements of group VIA are typical nonmetals. They are sometimes known, as the, chalcogens, from the Greek word meaning "ash formers". In their binary compounds with metals they exist as ions having a charge of 2-. The elements of group ⅦA are all nonmetals and are known as the halogens. from the Greek term meaning "salt formers. ” They are the most reactive nonmetals and are capable of reacting with practically all the metals and with most nonmetals, including each other. 除了钋的元素，VIA族元素是典型的非金属。他们是众所周知的硫族元素，这来自于希腊字母，词意是“灰的创造者”。在他们与金属离子形成的二元化合物中离子带2-价的电荷。ⅦA族的元素都是非金属，被称为卤素，来自希腊术语，意即“盐的创造者”。他们是最具有反应活性的非金属，能够与所有的金属和大多数非金属反应，包括互相之间的反应。 The elements of groups ⅥB, ⅦB, and VIIIB are all metals. They form such a wide Variety of compounds that it is not practical at this point to present any examples as being typical of the behavior of the respective groups. ⅥB，ⅦB，和VIIIB族元素都是金属。它们形成了各种各样的化合物，在这一点上我们甚至不能举出任何能表现各族元素典型变化的例子。 The periodicity of chemical behavior is illustrated by the fact that， excluding the first period, each period begins with a very reactive metal. Successive element along the period show decreasing metallic character, eventually becoming nonmetals, and finally, in group ⅦA, a very reactive nonmetal is found. Each period ends with a member of the noble gas family. 除了第一个周期，化学行为的周期性可以用事实说明，每一个周期以一个非常活泼的金属开始。沿着周期元素显示出了逐渐减少的金属性，最终成为非金属，最后，在ⅦA族，可以发现一个很活泼的非金属元素。每一个周期的结尾是一个稀有气体元素。 02 THE NONMETAL ELEMENTS 02非金属元素 We noted earlier that -nonmetals exhibit properties that are greatly different from those of the metals. As a rule, the nonmetals are poor conductors of electricity (graphitic carbon is an exception) and heat; they are brittle, are often intensely colored, and show an unusually wide range of melting and boiling points. Their molecular structures, usually involving ordinary covalent bonds, vary from the simple diatomic molecules of H2, Cl2, I2, and N2 to the giant molecules of diamond, silicon and boron. 很早我们就已经注意到非金属表现出了与金属不一样的特性。一般来说，非金属是比较差的电子（石墨碳除外）和热的导体；他们是易碎的，通常具有较强的颜色，并表现出很宽范围的熔点和沸点。他们的分子结构，通常是包括了普通的共价键，从简单的双原子分子的H2，Cl2，I2和N2到钻石、硅和硼的大分子。 The nonmetals that are gases at room temperature are the low-molecular weight diatomic molecules and the noble gases that exert very small intermolecular forces. As the molecular weight increases, we encounter a liquid (Br2) and a solid (I2) whose vapor pressures also indicate small intermolecular forces. Certain properties of a few nonmetals are listed in Table 2. 在室温下是气相的非金属是低分子质量的双原子分子和施加了非常小的分子间作用力的稀有气体。随着分子量的增大，我们遇到了一个液体(Br2)和一个固体(I2)，其蒸气压也表明小的分子间作用力。一些非金属的某些性质列在表2中。 Table 2 Molecular Weights and Melting Points of Certain Nonmetals Diatomic Molecules Molecular Weight Melting Point °C Color H2 2 -239.1' None N2 28 -210 None F2 38 -223 Pale yellow O2 32 -218 Pale blue Cl2 71 -102 Yellow — green Br2 160 -7.3 Red — brown I2 254 113 Gray—black Simple diatomic molecules are not formed by the heavier members of Groups V and VI at ordinary conditions. This is in direct contrast to the first members of these groups, N2 and O2. The difference arises because of the lower stability of π bonds formed from p orbitals of the third and higher main energy levels as opposed to the second main energy level2. The larger atomic radii and more dense electron clouds of elements of the third period and higher do not allow good parallel overlap of p orbitals necessary for a strong π bond. This is a general phenomenon — strong π bonds are formed only between elements of the second period. Thus, elemental nitrogen and oxygen form stable molecules with both σ and π bonds, but other members of their groups form more stable structures based on σ bonds only at ordinary conditions. Note3 that Group VII elements form diatomic molecules, but π bonds are not required for saturation of valence. 通常情况下，V和VI族包括的更重的元素不能形成简单的双原子分子。这与这两个族中所包括的第一种元素是直接相反的，N2和O2。差别的出现是由于与第二主能级相反，第三和更高主能级的p轨道形成的π键稳定性较低。第三和更高周期元素的更大的原子半径和更密的电子云不允许一个强的π键所必需的p轨道很好的平行重叠。这是一个普遍的现象—强的π键仅仅在第二周期的元素之间形成。因此，氮和氧元素形成了具有σ和π键的稳定分子，但是在通常情况下，这两个族的其他元素可以形成仅仅基于σ键的更稳定的结构。需要注意的是第VII族元素形成了双原子分子，但是π键不需要用于价态的饱和。 Sulfur exhibits allotropic forms. Solid sulfur exists in two crystalline forms and in an amorphous form. Rhombic sulfur is obtained by crystallization from a suitable solution, such as CS2, and it melts at 112°C. Monoclinic sulfur is formed by cooling melted sulfur and it melts at 119°C. Both forms of crystalline sulfur melt into S-gamma, which is composed of S8 molecules. The S8 molecules are puckered rings and survive heating to about 160°C. Above 160°C, the S8 rings break open, and some of these fragments combine with each other to form a highly viscous mixture of irregularly shaped coils. At a range of higher temperatures the liquid sulfur becomes so viscous that it will not pour from its container. The color also changes from straw yellow at sulfur's melting point to a deep reddish-brown as it becomes more viscous. 硫具有同素异形体。固态硫存在两种晶形和一种无定形的形式。斜方硫通过在合适的溶液中结晶化获得，如CS2，在112°C时融化。单斜硫通过冷却融化的硫获得和单斜硫在119°C时融化。两种形式的晶体硫融化成S-gamma，它由S8分子组成。S8的分子起皱成环和加热到160°C仍然存在。超过160°C， S8环被破坏，其中的一些片段相互结合形成一个高粘度的形状不规则的混合物。在更高的温度范围液态硫变得黏度很高，以致于在容器中不能倒出。随着变得更粘稠，其颜色也从硫熔点时的稻草黄色变成红褐色。 As4 the boiling point of 444 °C is approached, the large-coiled molecules of sulfur are partially degraded and the liquid sulfur decreases in viscosity. If the hot liquid sulfur is quenched by pouring it into cold water, the amorphous form of sulfur is produced. The structure of amorphous sulfur consists of large-coiled helices with eight sulfur atoms to each turn of the helix; the overall nature of amorphous sulfur is described as3 rubbery because it stretches much like ordinary rubber. In a few hours the amorphous sulfur reverts to small rhombic crystals and its rubbery property disappears. 随着接近444°C的沸点，硫的大的螺旋状分子被部分降解和液态硫的黏度降低。如果把热的液态硫倒入到冷却水里骤冷，就会产生无定形硫。无定形硫的结构由具有8个硫原子的大的螺旋线组成；无定形硫的总特性被描述成是有弹性的，因为它可以类似于普通的橡胶伸张。几个小时之内无定形硫恢复成菱形晶体，和它的弹性性质消失。 Sulfur, an important raw material in industrial chemistry, occurs as the free element, as SO2 in volcanic regions, as H2S in mineral waters, and in a variety of sulfide ores such as iron pyrite FeS2, zinc blende ZnS, galena PbS and such, and in common formations of gypsum CaSO4 • 2H2O, anhydrite CaSO4, and barytes BaSO4 • 2H2O. Sulfur, in one form or another, is used in large quantities for making sulfuric acid, fertilizers, insecticides, and paper. 硫在工业化学中是一种重要的原材料，它以单质，在火山区域以SO2，在矿泉水中H2S，和各种硫化物出现，像黄铁矿FeS2，闪锌矿ZnS，方铅矿PbS等等，还有石膏CaSO4•2H2O，硬石膏CaSO4，以及重晶石BaSO4•2H2O等普通形态。硫或以某种方式，用于大量制造硫酸、肥料、杀虫剂、和纸张。 Sulfur in the form of SO2 obtained in the roasting of sulfide ores is recovered and converted to sulfuric acid, although in previous years much of this SO2 was discarded through exceptionally tall smokestacks. Fortunately, it is now economically favorable to recover these gases, thus greatly reducing this type of atmospheric pollution. A typical roasting reaction involves the change: 2 ZnS + 3 O2—2 ZnO + 2 SO2 在硫化物煅烧中获得的以SO2形式存在的硫被转化成硫酸，尽管在过去几年许多二氧化硫通过高烟囱排放出去。幸运的是，现在回收这些气体的成本是较低的，从而这可以大幅度地减少大气污染。典型的焙烧反应如下： 2 ZnS + 3 O2-2氧化锌+ 2二氧化硫 Phosphorus, below 800℃ consists of tetratomic molecules, P4. Its molecular structure provides for a covalence of three, as may be expected from the three unpaired p electrons in its atomic structure, and each atom is attached to three others6. Instead of a strictly orthogonal orientation, with the three bonds 90° to each other, the bond angles are only 60°. This supposedly strained structure is stabilized by the mutual interaction of the four atoms (each atom is bonded to the other three), but it is chemically the most active form of phosphorus. This form of phosphorus, the white modification, is spontaneously combustible in air. When heated to 260°C it changes to red phosphorus, whose structure is obscure. Red phosphorus is stable in air but, like all forms of phosphorus, it should be handled carefully because of its tendency to migrate to the bones when ingested, resulting in serious physiological damage. 在低于800℃时，磷由四原子分子组成，P4。它的分子结构提供了三个共价，可预期三个共价是由该原子结构中三个未成对的p电子形成的，且每个原子都与另外三个相接。不是严格的正交取向，即三个键互成90°，而是键角仅仅是60°。这种可能的收缩结构通过4个原子的相互作用来稳定（每一个原子与其他三个原子成键），但是它是化学上最活跃的磷的形式。这种形式的磷、白磷，在空气中能自发燃烧。当加热到260°C时，它转变成红磷，其结构是不确定的。红色是在空气中是稳定的，但是，就像所有形式的磷，它应该谨慎处理，因为当摄取时，它倾向于迁移到骨头，这会导致严重的生理伤害。 Elemental carbon exists in one of two crystalline structures — diamond and graphite. The diamond structure, based on tetrahedral bonding of hybridized sp3 orbitals, is encountered among Group IV elements. We may expect that as the bond length increases, the hardness of the diamond-type crystal decreases. Although the tetrahedral structure persists among the elements in this group — carbon, silicon, germanium, and gray tin — the interatomic distances increase from 1.54 A for carbon to 2.80 A for gray tin. Consequently, the bond strengths among the four elements range from very strong to quite weak. In fact, gray tin is so soft that it exists in the form of microcrystals or merely as a powder. Typical of the Group IV diamond-type crystalline elements, it is a nonconductor and shows other nonmetallic properties7. 碳元素存在两种晶体结构——金刚石和石墨。基于杂化的sp3轨道四面体成键的金刚石结构遇到第IV族元素。我们可能希望键长增加，金刚石类型的晶体硬度降低。虽然四面体结构的元素存在这个族-碳、硅、锗，和灰锡-原子间的距离由碳的1.54Å增加到灰锡的2.80 Å。因此，在这四个元素之间，键的强度由强变弱。事实上，灰锡是非常柔软的，以致于它以微晶或粉末形式存在。碳作为典型的第IV族金刚石型晶体的元素，它是不良导体，且显示其他非金属性质。 10 ALKANES 10 烷烃 Number of Isomers 同分异构体的数量 The compounds now assigned the generic name alkane are also referred to as saturated hydrocarbons and as paraffin hydrocarbons. The word paraffin, from the Latin parum affinis(slight affinity)refers to the inert chemical nature of the substances and is applied also to the wax obtainable from petroleum and consisting of a mixture of higher alkanes. 现在指定属名为烷烃的化合物也被叫做饱和烷烃和链烷烃。石蜡一词,来自拉丁语“parum affinis”(极少亲和性的) ,指的是化学惰性的物质,并也适用于从石油和高级烷烃混合物中的得到的蜡。 Derivation of the formulas of the pentanes (3 isomers), hexanes (5). and heptanes(9) has already demonstrated the sharp rise in diversity with increasing carbon content. 戊烷（3个同分异构体），己烷（5个同分异构体），和庚烷（9个同分异构体）的衍生物已经表明了随着C含量增加，衍生物的数量会大幅度的上升。 Normal Alkanes 正烷烃 Successive members of the series differ in composition by the increment CH2 and form a homologous series. Thus heptane and octane are homologous hydrocarbons; icosane is a higher homolog of methane. 这一系列中接连相邻的成员间组成不同，通过增加CH2形成同系物。因此，庚烷和辛烷是同系碳氢化合物；二十烷是甲烷的一个较高的同系物。 Saturated Unbranched — Chain Compounds and Univalent Radicals 饱和无支链的链状化合物和单价基团 The first four saturated unbranched acyclic hydrocarbons are called methane, ethane, propane and butane. Names of the higher members of this series consist of a numerical term, followed by "-ane" with elision of terminal "a" from the numerical term. Examples of these names are shown in the table below. The generic name of- saturated acyclic hydrocarbons (branched or unbranched) is “alkane.” 前四个饱和无支链的非环状碳氢化合物被称为甲烷，乙烷，丙烷和丁烷。这一系列中更高的成员的命名包含一个数字项，紧接着是-ane，其中数字项结尾省略了a。这些名称的例子如下表所示。（含支链或非支链 ）的饱和无环碳氢化合物通用都被称作“烷烃”。 Examples of names: (n = total number of carbon atoms) 实例名称：(n =碳原子的总数) n n n 1 Methane 甲烷 15 Pentadecane 十五烷 29 Nonacosane 二十九烷 2 Ethane乙烷 16 Hexadecane 十六烷 30 Triacontane 三十烷 3 Propane 丙烷 17 Heptadecane 十七烷 31 Hentriacontane 三十一烷 4 Butane 丁烷 18 Octadecane 十八烷 32 Dotriacontane 三十二烷 5 Pentane 戊烷 19 Nonadecane 十九烷 33 Tritriacontane 三十三烷 6 Hexane 己烷 20 Icosane 二十烷 40 Tetracontane 四十烷 7 Heptane 庚烷 21 Henicosane 二十一烷 50 Pentacontane 五十烷 8 Octane 辛烷 22 Docosane 二十二烷 60 Hexacontane 六十烷 9 Nonane 壬烷 23 Tricosane 二十三烷 70 Heptacontane 七十烷 10 Decane 癸烷 24 Tetracosane 二十四烷 80 Octacontane 八十烷 11 Undecane 十一烷 25 Pentacosane 二十五烷 90 Nonacontane 九十烷 12 Dodecane 十二烷 26 Hexacosane 二十六烷 100 Hectane 一百烷 13 Tridecane 十三烷 27 Heptacosane 二十七烷 132 Dotriacontahectane 132烷 14 Tetradecane 十四烷 28 Octacosane 二十八烷 Saturated branched acyclic hydrocarbon is named by prefixing the designations of the side chains to the name of the longest chain which is numbered from one end to the other by Arabic numerals, the direction being so chosen as to give the lowest numbers possible to the side chains. When series of locants containing the same number of terms are compared term by term, that series is "lowest" which contains the lowest number on the occasion of the first difference1. This principle is applied irrespective of the nature of the substituents. 饱和的支链无环烃的命名是把侧链名称作为最长链名称的前缀，最长链用阿拉伯数字从一端到另一端进行编号，方向选择是为了让侧链的编号尽可能低。当位次含有相同编号的系列被逐级比较时，直到出现第一个不同，最低编号的那个体系就是最低的。这一原则适用与不考虑取代基的种类。 The presence of identical unsubstituted radicals is indicated by the appropriate multiplying prefix di-, tri-, tetra-, penta- , hexa- , hepta-, octa- , nona-, deca , etc. 存在相同未取代基团通过适当增加前缀二，三，四，五，六，七， ，八，九，十等来表示。 Univalent radicals derived from saturated acyclic hydrocarbons by removal of hydrogen from a terminal carbon atom are named by replacing the ending " — ane" of the name of the hydrocarbon by "—yl". The carbon atom with the free valence is numbered as 1. As a class, these radicals are called normal, or unbranched chain, alkyls. 单价基团是从饱和无环烃中去掉端基碳原子上的氢得来，用－yl代替烷烃名字结尾中的－ane来命名。具有自由价的碳原子编号为1 。作为一类，这些基团被称为正烷基或非支链烷基。 Stability. — Alkanes are relatively inert, chemically, since they are indifferent to reagents which react readily with alkenes or with alkynes. n-Hexane, for example, is not attacked by concentrated sulfuric acid, boiling nitric acid, molten "sodium hydroxide, potassium permanganate, or chromic acid; with the exception of sodium hydroxide, these reagents all attack alkenes at room temperature. The few reactions of which alkanes are capable require a high temperature or special catalysis. 稳定性。烷烃在化学上是相对惰性的，因为他们和与烯烃或炔烃反应的试剂不反应。例如，正己烷不与浓硫酸，沸腾的硝酸，熔融的氢氧化钠，高锰酸钾，或铬酸;除氢氧化钠，这些试剂都与烯烃在室温下反应。少数烷烃可以参加的反应 要求 对教师党员的评价套管和固井爆破片与爆破装置仓库管理基本要求三甲医院都需要复审吗 较高的温度或特殊催化。 Halogenation. —If a test tube containing n-hexane is put in a dark place and treated with a drop of bromine, the original color will remain undiminished in intensity for days. If the solution is exposed to sunlight, the color fades in a few minutes. and breathing across the mouth of the tube produces a cloud of condensate revealing hydrogen bromide as one reaction product. The reaction is a photochemical substitution: 卤化：如果把一个装有正己烷的试管放在黑暗的地方加一滴溴，原来的颜色将在强度上维持不退色好几天。如果溶液暴露在阳光下，颜色几分钟就消失了。试管口产生冷凝物，表明生成了HBr。这个反应光是化学取代反应： Chlorination of alkanes is more general and more useful than bromination and can be effected not only photochemically but also by other methods. 烷烃的氯化比烷烃的溴化更普遍和更有用，而且不仅可以通过光化学而且还可以通过其他 方法 快递客服问题件处理详细方法山木方法pdf计算方法pdf华与华方法下载八字理论方法下载 实现。 Light initiates chlorination of an alkane by converting chlorine molecules into chlorine atoms by a process of hemolysis, in which a covalent bond is severed and one electron is retained by each of the atoms forming the bond: Cl:Cl —→Cl • + C1• . A chlorine atom has an odd, or unpaired electron and is a free radical. Because of the tendency of atoms to attain their normal valence shells, any free radical is a highly reactive species. Photochemical chlorination proceeds through a succession of free radicals; it is a free radical chain reaction. The chain initiating step (1 ), hemolytic fission of chlorine molecules, produces chlorine free radicals; in chain propagating steps, a chlorine radical attacks a molecule of alkane to produce hydrogen chloride and an alkyl radical (2), which in turn attacks a chlorine molecule to produce a chloroalkane and a chlorine radical (3). 光引发烷烃的氯化通过均裂的形式将氯分子转化为氯原子。其中的共价键断了，每个原来形成键的原子分别保留一个电子。一个氯原子有一个奇数的，或者未成对电子成为一个游离基。由于原子倾向得到正常的价电子，任何游离基都是高活性的物种。光化学氯化通过游离基的传导实现，它是游离基的链反应。链引发步骤（ 1 ），氯分子的均裂，产生了氯游离基;在链传播步骤，一个氯游离基攻击烷烃分子产生氯化氢和烷基游离基（ 2 ） ，而他又反过来攻击氯分子产生氯代烷烃和氯游离基（ 3 ） 。 Since chlorine-radicals required in step (2) are regenerated in step (3), the two reactions together constitute a chain which, if both reactions proceeded with perfect efficiency, would be self-propagating without further requirement of light energy, The efficiency. however. is not perfect, for chlorine radicals can recombine (4), combine with alkyl radicals ( 5), or dissipate energy by collision with the flask wails. Hence continued radiation is required to maintain an adequate supply of initiating radicals. The chain initiating step requires input of light energy amounting to + 242.8kJ/mole. Step (2), however, is exothermic, since the energy required to break the C — H bond is less than the bond energy of H — Cl. The second chain propagating step (3) is likewise exothermic, and indeed chlorination of an alkane can proceed explosively. 由于在步骤（ 2 ）中需要的氯游离基在步骤（ 3 ）中再生了 ，这两个反应共同构成链，如果两个反应都有较高的效率，反应将是自延续的，不再需要进一步的光能。然而，效率并不非常好，氯游离基可以重组（ 4 ） ，并结合烷基（ 5） ，或通过与瓶壁碰撞来消耗能量。因此，需要继续辐射来维持提供充足的自由基。链引发步骤需要投入光能达+ 242.8kJ/mole 步骤（ 2 ）然而，是放热的，因为所需的打破C - H键的能量少于H — Cl键的能量。第二个链传递步骤（ 3 ）同样是放热，实际上烷烃的氯化可以爆炸式的发生。 Cracking. —Heated to temperatures in the range 500 ~ 700°, higher alkanes undergo pyrolytic rupture or cracking to mixtures of smaller molecules, some saturated and some unsaturated. Unsaturated hydrocarbons produced by selective cracking of specific petroleum fractions are useful in chemical synthesis. Cracking ruptures carbon — carbon rather than carbon —hydrogen bonds because the energy required to break the C —C bond is 247kJ/mol, whereas the C — H bond energy is 364kJ/mol. 裂解：加热温度在500 〜 700 ℃ 范围内，高烷烃进行热解或裂解成为小分子的混合物，包括一些饱和不饱和的。通过选择性裂解特殊石油馏分得到的不饱和烃在化学合成上是非常有用的。裂解断裂的碳-碳键而不是碳氢键，因为打破C - C原子键所需的能量是247kJ/摩尔，而打破C - H键的能量是364kJ/mol。 Oxidation. —The reaction of hydrocarbons with oxygen with the output of energy is the basis for use of gasoline as fuel in internal combustion engines. The energy release on burning a given hydrocarbon is expressed as the heat of combustion in terms of kJ/mole. 氧化。碳氢化合物与氧反应放出能量是使用汽油作为内燃机燃料的基础。燃烧某一特定的碳氢化合物所释放的能量用燃烧热来表示，单位是千焦耳/摩尔。 Incomplete combustion of gaseous hydrocarbons is important in the manufacture of carbon blacks, particularly lampblack, a pigment for ink, and channel black, used as a filler in rubber compounding. Natural gas is used because of its cheapness and availability; the yield of black varies with the type of gas and the manufacturing process but usually is in the range of 2~6% of the theoretical amount. 气态烃的不完全燃烧在工业上生产炭黑上很重要，尤其是灯黑，一种墨水颜料，和槽法炭黑，用作橡胶配方的填料。天然气的使用，因为其廉价和可实用性;黑的产率根据气体种类的不同以及制造工艺的不同而不同，但通常是理论数额的2 〜 6 ％。 Partial air oxidation of a more limited extent is a means for production of specific oxygenated substances. Controlled air oxidation of high-boiling mineral oils and waxes from petroleum affords mixtures of higher carboxylic acids similar to those derived from fats and suitable for use in making soaps. 空气部分氧化到一定限度是生产特殊氧化物制的一种手段，高沸点矿物油和石油中的蜡的可控空气氧化得到了类似于来自脂肪的高级羧酸混合物，适合用于制作肥皂。 24 VOLUMETRIC ANALYSIS 24 容量分析 General principles 一般原则 Chemical analyses can be made by determining how much of a solution of known concentration is needed to react fully with an unknown test sample1. The method is generally referred to as volumetric analysis and consists of titrating the unknown solution with the one2 of known concentration (a standard solution). By titration, you can determine exactly how much of a reagent is required to bring about complete reaction of the test solution. Usually, completion of the reaction is indicated by a sudden, visible change in the reaction system that coincides with the stoichiometric relationship between moles or equivalents of-the reagent solution and the reactant in the test solution, A drop or two of an appropriate indicator solution produces a color change at the point where the reaction is complete-referred to as the endpoint. 化学分析是用来确定要用多少已知浓度的溶液与未知试样完全反应。这种方法就是通常所说的容量分析，它用一种已知溶液（ 标准 excel标准偏差excel标准偏差函数exl标准差函数国标检验抽样标准表免费下载红头文件格式标准下载 溶液）标定未知溶液。通过滴定，你能精确的知道需要多少试剂才能导致（使）待测溶液完全反应。通常，反应的完成是通过在反应体系中的突然的可见的变化来表明的，而这种突变和试剂溶液与待测溶液中的反应物的摩尔或当量的化学计量关系一致，一两滴适当的指示剂溶液在反应完成，也就是反应终点时产生一种颜色的变化。 Molarity is the number of moles (gram-molecular weights)of substance per liter of solution. The mole weight of sulfuric acid is 98.08 g, and therefore, 1 mole of H2SO4 contains 98.08 g. If 49.04 g are diluted to 1 liter then the concentration is 0.49 or 0.5M. In the case of hydrochloric acid, HCl, a 1 M solution is prepared by taking 36.465 g of HC1 and diluting to 1 liter. The procedure is the same for bases. 摩尔浓度是每升溶液中物质的摩尔（克分子量）数。硫酸的分子量是98.08g，因此，1摩尔硫酸含98.08g.如果49.04g被稀释至1升，浓度就变为0.49或0.5M。如果是盐酸，加入36.465g的HCl稀释到1升可制成1M的溶液。这个手段同样适用于碱。 Normality is the number of equivalent weights of substance per liter of solution. The equivalent weight of an acid is the weight of that acid capable of furnishing 1 mole of protons (H+), and the equivalent weight of a base is the weight of base capable of receiving 1 mole of protons. The equivalent weight of H2SO4 is 98.08g/2 or 49.04 g. Therefore, a normal solution (N) of H2SO4 contains 49.04g per liter. 当量浓度是每升溶液的物质的当量。酸的当量是指能够提供1摩尔H+的酸的量，碱的当量是指能够获得1摩尔H+的碱的量。硫酸的当量是98.08g/2或者49.04g。因此，标准的硫酸溶液每升含49.04g. The normality of an acid or base of unknown concentration may be determined by titration. The advantage of using normality rather than molarity is that equal volumes of solutions of equal normalities have identical capacities for neutralization, because they contain the same number of equivalent weights。 未知浓度的酸或碱的当量浓度可以通过滴定来确定。用当量浓度而不是摩尔浓度的优势在于等体积的等当量浓度的溶液有相同的中和能力，因为它们包含相同的当量数。 In a titration, we compare equivalent weights of acid and base. The number of equivalents of acid is equal to the product of the volume of the acid solution and its normality: 在滴定中，我们比较酸和碱的当量。酸的当量等于酸溶液的体积和它的当量浓度的乘积。 Va × Na = equivalents of acid Va × Na = 酸的当量 The number of equivalents of base is the product of the volume of the base solution and its normality: 碱的当量等于碱溶液的体积和它的当量浓度的乘积。 Vb × Nb = equivalents of base Vb × Nb = 碱的当量 That's true because: (volume)(normality) = (liters)(equivalents/liter) = equivalents 这是正确的，因为 体积×当量浓度=升×（当量/升）=当量 Neutralization has taken place when the number of equivalents of acid is equal to the number of equivalents of base: 当酸的当量等于碱的当量时中和反应就发生了 Va × Na = Vb × Nb Procedure 程序 Care must be exercised throughout the titration procedure3. The burette should be thoroughly cleaned with soap and water, rinsed with tap water, and finally, rinsed with distilled water. Just before use, the burette should be rinsed with two 5-ml portions of the solution to be used in the burette. This is done by holding the burette in a semi-horizontal position and rolling the solution around the entire inner surface. Allow the final rinsing to drain through the tip. 整个滴定过程一定要小心。滴定管一定要用肥皂和水完全清洗干净，再用自来水，最后用蒸馏水润洗。在用之前，滴定管用两份5毫升的要在滴定管中用的溶液清洗。在半水平方向握住滴定管，绕着滴定管的内部表面旋转溶液。让剩下的溶液从滴定管末端流出。 Fill the burette to a point above the top marking and allow the solution to run out until the bottom of the meniscus is just at the top marking of the burette. The burette tip must be completely filled to deliver the volume measured. 填充滴定管在最大刻度以上，允许溶液流出直到弯液面的底端正好在滴定管的最上端刻度。滴定管底部必须被完全填充以便测量体积。 In addition, the burette must be cleaned thoroughly after use because sodium hydroxide and other types of solutions will eventually frost the glass and render an expensive piece of equipment useless. 另外，在使用后滴定管必须被完全清洗干净，因为氢氧化钠和其它一些溶液将会腐蚀玻璃，致使价格比较贵的仪器不能使用。 1. Titration of Vinegar 1. 醋酸的滴定 Measure 50 ml of vinegar with a pipette and pour into a 250-ml beaker. Add 2 drops of phenolphthalein indicator. Fill a burette with a 1 N solution of sodium hydroxide (NaOH) and draw out the excess as described above. From the burette add NaOH to the beaker of vinegar until 1 drop of NaOH produces a pale pink color in the solution. Maintain constant stirring. The appearance of pink tells you that the acid has been neutralized by the base and there is now 1 drop of excess base which has turned the indicator. Read the burette and record this reading as the volume of base used to neutralize the acid. 用移液管移取50毫升的醋酸倾倒到250毫升的烧杯中。加两滴酚酞指示剂。用1N的氢氧化钠填充滴定管，按照上面所说的赶出过多的溶液。从滴定管中滴加氢氧化钠至醋酸容器中直到一滴氢氧化钠的加入后产生浅粉色。保持不断搅拌。粉色的出现表明酸已经被碱中和了，正是过量的一滴碱使指示剂变色。读滴定管，记录用于中和酸的碱的体积。 According to the equation; NaOH + CH3COOH → Na+ + CH3COO- + H2O 根据等式： NaOH + CH3COOH → Na+ + CH3COO- + H2O One molecule of NaOH neutralizes one molecule of acetic acid, or one gram-molecular weight of NaOH neutralizes one gram-molecular weight of acetic acid. Calculate the amount of acetic acid present in the vinegar. Report this amount as the percentage of acetic acid. 一分子的氢氧化钠中和一分子醋乙酸，或者是一克分子量的氢氧化钠中和一克分子量的乙酸。计算在醋酸中乙酸的量。报这个数为乙酸的百分数。 2. Standard Titration Curve 2. 标准滴定曲线 If a pH meter is available, repeat the above process using a pH meter for constantly determining the pH. When the endpoint is reached, continue adding the base to expand the curve further. Make a graph for this titration. 如果可以获得一个PH计，用一个PH计重复上面的过程，不断地测量PH值。当到达终点的时候，继续滴加碱以扩展这个曲线。对这个滴定绘制一个图。 3. Equivalents of Acid 3. 酸的当量 Using the 1 N solution of NaOH, determine the number of equivalents in two samples of benzoic acid. Carry out the procedure for the two determinations simultaneously. From this value calculate the equivalent weight of the acid. The solid should be weighed in a beaker and should be dissolved in about 25 ml of ethyl alcohol before titration with the base. Between 2.0 and 2.2 g of the solid provide the best results. Record all data and make all calculations necessary to determine the equivalent weight of the solid acid. Compare your experimental value with the equivalent weight of benzoic acid (calculated from the formula) and determine the percentage of error of your work. 用1N的氢氧化钠测试两个安息香样品的当量数。同时进行这两个测定。从中计算酸的当量。在与碱的滴定之前固体应当在烧杯中称量再溶解在大约25毫升的乙醇中。 2.0到2.2g的固体量是最佳的。记录所有的数据，进行所有必要的计算来得到固体酸的当量。对比你的实验数据和苯甲酸的当量（从分子式中计算的）来确定你的工作误差的百分率。 Questions to Consider 思考 题 快递公司问题件快递公司问题件货款处理关于圆的周长面积重点题型关于解方程组的题及答案关于南海问题 (l)Calculate the percentage, of acetic acid in vinegar. 计算在醋中乙酸的百分率。 (2)What is the pH range for phenolphthalein? 对于酚酞的PH的范围。 (3)Why should the solution in the flask constantly be stirred? 为什么溶液在烧杯中要不断地搅拌？ (4)What determines the pH of a solution at the end of a titration of an acid with a base? 在酸和碱的滴定终点什么决定PH？ (5)Consider a hypothetical experiment in which you weighed out 2.0 g of oxalic acid and titrated it with 43 ml of 1.5N NaOH. What is the equivalent weight of oxalic acid? 考虑一个假定的实验，你称量了2.0g的酢浆草酸，用43毫升1.5N的氢氧化钠滴定了它，那么，这个酢浆草酸的当量是多少？ (6)When all of the acetic acid was neutralized by the sodium hydroxide, was the pH = 7? Explain. 当所有的乙酸被氢氧化钠中和掉时，PH=7吗? 解释。 31 THE CHEMICAL THERMODYNAMICS 31 化学热力学 The branch of science which includes the study of energy transformations is called thermodynamics. Basic to thermodynamics are two "laws" derived from experience, which can be stated as follows; 1. Energy can neither be created nor destroyed — the energy of the universe is constant. 2. The entropy of the universe is always increasing. 热力学作为一个分支科学主要研究的是能量的转化。热力学的基础是两条从经验中 总结 初级经济法重点总结下载党员个人总结TXt高中句型全总结.doc高中句型全总结.doc理论力学知识点总结pdf 出来的“定律”，下面将给出这两条定律的详细解释： 1．能量不会产生也不会消亡，即宇宙中的能量是守恒的。 2．宇宙的熵是不断增长的。 These generalizations are statements of the first and second laws of thermodynamics. The laws and the meaning of entropy will be discussed and expanded upon in this lesson. It will be shown that energy transformations on a macroscopic scale — that is, between large aggregates of atoms and/or molecules — can be understood in terms of a set of logical principles. Thus thermodynamics provides a model of the behavior of matter in bulk. The power of such a model is that it does not depend on atomic or molecular structure. Furthermore, conclusions about a given process . based on this model, do not require details of how the process is carried out. Applied to chemistry, thermodynamics provides criteria for predicting whether a given reaction can occur. If a reaction is feasible, the extent to which it will proceed under a given set of conditions can be predicted. One great value of thermodynamics is that it is possible to use data from experiments which can be conveniently carried out to arrive at conclusions about experiments which are difficult or even impossible to perform. 这些总结就是热动力学的第一、第二定律的陈述。我们会在这一课讨论并阐述这两条定律以及熵的概念。热动力学体现了微观状态下的能量的转化即在原子或分子簇间进行的过程，我们可以通过一系列合理的原理来理解它。因此，热动力学提供了在宏观状态下物质行为的模型。这类模型的优势在于它并不依赖原子或分子的结构。更要强调的是，依据模型得出的关于给定过程的结论并不需要关于这个过程是怎样得出的细节。当应用于化学时，热动力学为预测给定反应是否会发生提供了准据。如果一个反应易发生，在一系列给定条件下反应进行的程度可以被预测。热力学在化学反应中的一个重要应用是它可以在很大程度上通过试验中较方便得到的数据来推断出一些很难或不可发生的实验的结论。 Systems. Initial States. Final States 系统。始态。终态 At the outset, it is worthwhile to define some terms which are customarily used in discussing the interactions of energy with matter. That portion of matter which is being investigated is called the system. All other objects in the universe which may interact with (he system are called the surroundings. For example, 1 liter of a 1 M aqueous solution of sodium chloride may be under investigation. The solution's container would be considered part of the surroundings. A system is described hv identifying its constituents and their quantities, the temperature, the pressure, and perhaps some other relevant conditions . such as the physical states of the substances involved. A complete description of the system defines its state. The initial state of a system is its state before, it undergoes a change, and the final state describes the system after a change has occurred. In going from the initial state to the final state, a system may exchange energy with its surrounding, and/or its components may change composition; but there can be to change in the total mass of the system. No matter can be lost to or gained from the surroundings. 首先，我们很有必要来定义几个通常在讨论能量交互转化问题中使用的术语。我们定义物质被研究的部分为体系。其他所有的可能与体系发生相互作用的物体被定义为环境。例如，研究一升1M的氯化钠水溶液。溶液的容器就可以被认为是环境。一个体系可以用鉴定其组成成分、含量、温度、压力、以及其他可能相关的条件，比如，物质所处的物理状态等来描述。一个体系完整的描述就可以确定它的状态。一个体系的始态是它没有经历变化前的状态，终态则描述了变化发生后的状态。在由始态向终态转化的过程中，体系可能会与环境发生能量交换，并且体系的组成成分会改变组合方式：但是体系的总质量是不会改变的。体系不能通过环境获得或失去其所含的物质。 The properties of a system which uniquely define the state of the system are called thermodynamic properties or state functions. For example, consider a system consisting of one mole of an ideal gas. The state of the system is specified by giving any two of the properties pressure, volume, and temperature. As was described in the previous chapter, the pressure, F, volume, V, and temperature ,T, of n moles of an ideal gas are related by the equation PV = nRT 我们把系统中能够唯一确定这个系统状态的性质称为该系统的热力学性质，或者叫态函数。例如，考虑含1mol理想气体的系统。该系统的状态能够通过给出它的压强，体积，温度中的任意两个来确定。我们在前一章讨论过，n mol理想气体的压强P，体积V，以及温度T可以通过下面这个方程联系起来： PV = nRT This equation, expressing the relationship of its state functions, is called the equation of state for an ideal gas. The equations of state for real gases, liquids, solids and solutions are more complicated than that for an ideal gas. When a system undergoes a change in state, the change, in value of any state function depends only on the initial and final states of the system and not on how the change is accomplished. Indeed, as will be shown, the importance. 01 state functions lies in the fact that for a given system, the change in their values can be obtained by considering only the initial and final states of the system. 这个体现态函数间联系的方程称作理想气体的状态方程。真实气体，液体，固体以及溶液的状态方程要比理想气体的复杂的多。当一个系统的状态发生变化时，任何态函数的值的变化仅和系统的初态和末态有关，而与变化是怎样形成的无关。在后面我们会看到，态函数的重要性正是体现在对于任一给定系统，它的值的改变可以通过只考虑系统的初末态而得到。 When a system undergoes a reaction described by a chemical equation, the description of the reactants defines the initial state of the system, and the corresponding description of the products defines the final state. 当一个系统进行一个用化学方程表述的反应时，反应物的种类就决定了这个系统的初态，相应的产物的种类决定了系统的末态。 The properties of a system which do not depend on the quantity of matter present are called intensive properties. For example. density, pressure, and temperature are intensive properties. Properties which are proportional to the quantity of matter in the system are called extensive properties. The mass of a sample is an extensive property. 系统的性质中不依赖于物质的数量的性质称为强度性质。例如，密度，压强，温度就是强度性质。而和系统中物质的数量有关的性质称作量度性质。如样品的质量是量度性质。 Heat Capacity 热容量 The quantity of heat required to raise the temperature of 1 gram of any substance 1 degree. Celsius is called the specific heat capacity of that substance, or more simply its specific heat. The quantity of heat necessary to raise the temperature of 1 mole of a substance 1 degree Celsius is called its molar heat capacity. 将1克物质的温度升高1摄氏度所需要的热量称作该物质的比热容，或者简称比热。把1摩尔物质的温度升高1摄氏度所需要的热量称作该物质的摩尔热容。 The First Law of Thermodynamics 热力学第一定律 Any system in a given state will possess a given quantity of energy . called its internal energy, K. Internal energy is an extensive properly. By either releasing energy or by absorbing energy, a system may change from an initial state where its internal energy is E1 to a different (final) state where its internal energy is E2. The change in internal energy is ΔE = E2 - E1 任何一个给定状态的系统都会有一个给定的能量，叫做系统内能，用E表示。内能是一个广泛的性质。通过释放和吸收能量，一个系统的内能会从最初状态E1转变成最终的状态E2.内能的变化为 ΔE = E2 - E1 It is seldom necessary (and of little practical use) to know the individual values of energies E1 and E2. The difference in energy between two states is of prime importance and is usually conveniently determined. The change (increase or decrease) of energy in a given system was determined from its mass, its heat capacity, and the change in temperature. At no time was the total energy of the system considered; only the gain or loss of heat was found. 知道单个状态的能量E1，E2是没有什么意义的。两个状态在能量上的不同才是最重要，也是更方便确定的。一个给定系统的能量（增加或减少）的变化是由它的质量，热容量，温度的变化决定。我们自始至终没有考虑系统的总能量，仅仅考虑了系统能量的得与失。 Energy may be transferred into or out of a system in forms other than heat. For example a chemical system may transfer mechanical energy through expansion of a gaseous product. With proper experimental arrangement, electrical energy may be obtained from a chemical system. It is customary to denote all forms of transferred energy other than heat as work, w. Thus when a system changes from one state to another, the change in its internal energy is given by. ΔE = q + w 能量也可以通过除了加热以外的方法转入或转出系统。如一个化学的系统可以通过气体产物的膨胀把内能转化为机械能。通过合适的实验，电能可以从一个化学的系统中获得。 习惯上把除了加热以外的能量转换方式表示为功，用W表示。因此一个系统从一个状态变为另一个状态，其内能的变化可以表示为 ΔE = q + w where q is the heat absorbed by the system and w is the work done on the system. The relationship ΔE = q+w is a mathematical statement of the first law of thermodynamics — energy can neither be created nor destroyed. q 代表系统吸收的热能，w 代表作用在系统上的功。△E =q + w 是热力学第一定律在数学上的表示—— 能量既不会被创造也不会毁灭。 Enthalpy 焓 In the laboratory, many chemical reactions are carried out in open containers. When a reaction takes place in contact with the atmosphere, the volume of the system will change in such a way that the final pressure of the system equals the atmospheric pressure. Since the atmospheric pressure does not usually change significantly over a period-of hours, a reaction occurring in an open vessel may be considered to be a constant pressure process. Any change in the volume of the reaction system Would result in work being done against the constant pressure of the atmosphere. 在实验室，很多化学反应是在敞开的容器里进行的。当一个化学反应在与大气压相连的容器下反应时，系统会改变体积使系统最后的压力等于大气压。而通常情况下大气压在有意义的几小时内是不变的，所以反应在敞开的容器下反应可以被看成是恒压反应过程。反应系统体积的变化导致做克服大气恒压的功。 Free Energy and Entropy —Criteria for Spontaneous Change 自由能，熵——衡量自然变化 A major objective of chemists is to understand and control chemical reactions — to know whether or not under a given set of conditions two substances will react when mixed, to predict the extent to which a given reaction will proceed before equilibrium is established, and to determine whether or not a given reaction will be endothermic or exothermic. 化学家的主要目的是去理解和控制化学反应——去了解在一给定条件下两物质混合是否会反应，在反应平衡确定前预计给定反应的反应程度，确定一个给定反应是否是吸热或放热反应。 The enthalpy change in a chemical reaction is a measure of the difference in energy content of the products and reactants. It is tempting to assume that exothermic reactions will proceed spontaneously upon mixing the reactants and that endothermic reactions do not occur spontaneously. However, there are endothermic reactions which do proceed spontaneously. 化学反应的焓变是用来衡量产物和反应物内能不同的。它引起了混合的反应物在放热反应时可以自发反应而吸热反应不能自发发生反应。然而也有吸热反应可以自发产生。 The transfer of heat energy from an object at a higher temperature to one at a lower temperature is a familiar example of a spontaneous process. It must be recalled that heat is a unique form of energy in that at constant temperature * heat can not be completely-converted to any other form of energy. 2 The heat content, or enthalpy, of any system must be considered in two parts: 1. That which is free to be converted to other forms of energy. 2. That which is necessary to maintain the system at the specified temperature and thus is unavailable for conversion. 一个处于更高温度的物体变为处于更低温度的物体的热能的变化是一个常见的自发过程。在恒温下，热能是唯一的能量形式，因为热能不能完全转化为其他形式的能。任何系统的热函或焓都必须考虑两个部分： 1，一是可以自由的被转化为其他形式的能。 2，一是需要在特别温度下维持系统，这样就不能转化的能量。 It is customary to solve the equation representing the second law of thermodynamics explicitly forΔG as follows: ΔG =ΔH- TΔS( constant T) and to apply the following criteria for spontaneous change and for the equilibrium state: 1. It ΔG is negative, the given process may occur spontaneously. 2. If ΔG is positive, the indicated process cannot occur spontaneously; instead the reverse of the indicated process may occur. 3. If ΔG is zero, neither the indicated process nor the reverse process can occur spontaneously. The system is in a state of equilibrium. The indicated process is said to be a reversible one because a very small change in conditions can make ΔG either positive or negative. 习惯上解决热力学第二定律的方程式的明确用△G表示如下： G = △H –T△S（恒温） 应用下面的标准来判断自发变化和反应平衡： 1．如果△G是负数，该过程可自发进行。 2．如果△G是正数，表示过程不能自发发生；不过其反过程可以自发产生。 3．如果△G是零，表示过程与其反过程都不能自发进行。系统处于平衡状态。该过程被称为可逆过程，因为条件很小的改变都可以让△G或正或负。