大学化工专业英语Lesson 2

Chemical Equilibrium and Kinetics

化学平衡和动力学

A major objective of chemist is to understand chemical reactions, to know whether under a given set of conditions two substances will react when mixed, to determine whether a given reaction will be exothermic or endothermic, and to predict the extent to which a given reaction will proceed before equilibrium is established.

化学家的一个主要目标是理解化学反应，知道在给定的一组条件下两种物质混合时能否发生反应；确定一个给定的反应放热还是吸热；预测一个给定的反应在平衡前进行的程度。

An equilibrium state, produced as a consequence of two opposing reactions occurring simultaneously, is a state in which there is no net change as long as there is no change in conditions.

两个相反的反应同时进行时的状态叫做平衡状态，在平衡状态下，只要条件不发生改变，这个状态就不会有净变化。

In this lesson it will be shown how one predict the equilibrium state of chemical systems from thermodynamic data, and conversely how the experimental measurements on equilibrium states provide useful thermodynamic data.

在这节课中，将会展示如何根据热力学数据来预测化学体系的平衡状态，以及相反地，平衡状态的实验测量如何提供有用的热力学数据。

Thermodynamics alone cannot explain the rate at which equilibrium is established, nor does it provide details of the mechanism by which equilibrium is established.

单纯的热力学无法解释建立平衡的速度，也不能提供平衡建立所遵循的机理信息。

Such explanations can be developed from considerations of the quantum theory of molecular structure and from statistical mechanics.

从分子结构的量子理论和统计力学的角度考虑可以使这样的解释得到发展。

To appreciate fully the nature of the chemical equilibrium state, it is necessary first to have some acquaintance with the factors which influence reaction rates.

要充分理解化学平衡状态的性质，首先必须熟知影响反应速率的因素。

The factors which influence the rates of a chemical reaction are temperature, concentrations of reactants(or partial pressures of gaseous reactants), and presence of a catalyst.

影响化学反应速率的因素有温度、反应物浓度（气体反应物的分压）和催化剂。 In general, for a given reaction the higher the temperature, the faster the reaction will occur.

一般来说，对于一个给定的反应，温度越高，反应速率越大。

The concentrations of reactants or partial pressure of gaseous reactants will affect the rate of reaction, an increase in concentration or partial pressure increases the rate of most reactions.

反应物浓度或气体反应物的分压影响反应的速率，对于大部分反应来说，增大浓度或分压，反应速率增大。

Substances which accelerate a chemical reaction but which themselves are not used up in the reaction are called catalysts.

可以加快反应速率但本身不参加反应的物质称为催化剂。

Dynamic Equilibrium

动态平衡

In many cases, direct reactions between two substances appear to cease before all of either starting material is exhausted.

在许多情况下，两种物质间的直接反应在所有原始物料耗尽之前就会停止。 Moreover, the products of chemical reactions themselves often react to produce the starting materials.

此外，化学反应自身的产物能够发生反应生成原始物料。

For example, nitrogen and hydrogen combine at 500 ℃ in the presence of a catalyst to produce ammonia:

N 2+3H 2=2NH 3

例如，在催化剂存在下，氮和氢在500℃能够反应生成氨：

N 2+3H 2=2NH 3

At the same temperature and in the presence of the same catalyst, pure ammonia decomposes into nitrogen and hydrogen:

2NH 3=3H 2+ N 2

在相同温度和相同催化剂存在下，纯净的氨能够分解生成氮和氢：

2NH 3=3H 2+ N 2

For convenience, these two opposing reactions are denoted in one equation by use of a double arrow:

22

3N 3H 2NH

为了方便起见，这两个反应能够用双箭头表示在一个方程式中：

223N 3H 2NH

The reaction proceeding toward the right is called the forward reaction; the other is called the reverse reaction.

向右进行的反应称为正反应，另外一个称为逆反应。

If either ammonia or a mixture of nitrogen and hydrogen is subjected to the above condition, a mixture of all the three gases will result.

如果将氨或氮气和氢气的混合物放在上述条件下，将都会产生三种气体的混合物。

The rate of reaction between the materials which were introduced into the reaction vessel will decrease after the reaction starts; because their concentrations are decreasing, conversely, after the start of the reaction the material being produced will react faster, since there will be more of it.

在反应开始后，放入反应器内的材料之间的反应速率将会减小；因为它们的浓度在减小，相反，在反应开始后，产物之间的反应将会加快，由于它们的浓度在增加。

Thus the faster forward reaction becomes slower, and the slower reverse reaction speeds up.

因此，较快的正反应变慢，较慢的正反应加快。

Ultimately the time comes when the rates of the forward and reverse reactions become equal, and there will be no further net change.

最后，正反应和逆反应速率变得相等，且不再有进一步净变化的时刻终于到来。 This situation is called equilibrium.

这种状态称为平衡状态。

Equilibrium is a dynamic state because both reactions are still proceeding; but since the two opposing reactions are proceeding at equal rates, no net change is observed. 平衡是动态的，因为反应仍然在进行；但是由于两个相反方向的反应以相同的速率进行，所以没有净变化被发现。

All chemical reactions ultimately proceed toward equilibrium.

所有的化学反应最后都要向平衡状态进行。

In a practical sense, however, some reactions go so far in one direction that the

reverse reaction cannot be detected, and they are said to go to completion.

然而，实际上，一些反应在一个方向上进行的很快以至于检测不到逆反应，据此可说它们进行完全了。

The principles of chemical equilibrium apply even to these, and it will be seen that for many of them, the extent of reaction can be expressed quantitatively.

化学平衡的原理甚至也适用于被认为是进行完全的反应，显然许多这类反应其反应程度可以定量地表达。

Equilibrium Constants

平衡常数

Equilibrium is a state of dynamic balance between two opposing processes. For a general reaction at a given temperature:

A+B=C+D

平衡是两个相反过程的动态平衡的一种状态。在给定温度下，对于一个普通的反应：

A+B=C+D

At the point of equilibrium, the following ratio must be a constant:

CD

K=

AB

在平衡时，以下比值肯定是一个常数：

CD

K=

AB

The constant, K, is called the equilibrium constant of the reaction.

常数K称为反应的平衡常数。

It has a specific value at a given temperature.

在一个给定温度下，它有一个比值。

If the concentration of any of the components in the system at equilibrium is changed, the concentrations of the other components will change in such a manner that the defined ratio remains equal to K as long as the temperature does not change.

如果平衡时体系中任意组分的浓度改变，那么只要温度不变，其他组分的浓度将以保持相等K的固定比例的方式变化。

The equilibrium constant expression quantitatively defines the equilibrium state.

平衡常数表达式定量地定义了平衡状态。

More generally, for the reversible reaction

aA bB cC dD +=+

更一般地说，对于一个可逆反应

aA bB cC dD +=+

the equilibrium constant expression is written as follows:

c d

a b C D A B

K = 平衡常数表达式可以写成：

c d

a b C D A B

K = By convention, the concentration terms of the reaction products are always placed in the numerator of the equilibrium constant expression.

按照惯例，反应产物浓度项通常是放在平衡常数表达式的分子上。

It should be noted that the exponents of the concentration terms in the equilibrium constant expression are the coefficients of the respective species in the balanced chemical equation.

应该注意的是，平衡常数表达式中浓度项的指数是平衡化学方程式中各个物种的系数。

Chemical Kinetics

化学动力学

When a system is in the equilibrium state, the rate of the forward reaction is identical to the rate of the reverse reaction.

当一个体系达到平衡状态时，正反应的反应速率等于逆反应的反应速率。

It is important to know just how fast a reactant is being used up in a process, or the speed with which a product is being formed.

重要的是，要知道在反应过程中，反应物消耗完的速率，或者产物生成的速率。 It is also important to have detailed information about rates of reactants in order to test theories and mechanisms for various kinds of chemical processes.

同样重要的是，要有关于反应物反应速率的详细信息，以便测试各种化学过程的理论和机制。

Experiments show that a number of reaction variables affect reaction rates:

实验表明，许多反应变量都影响反应速率：

Temperature. The rates of chemical reactions are temperature-dependent. Therefore, it is common practice when studying the rate in the laboratory to carry out reactions at constant temperature(isothermally), thus eliminating one variable.

温度。化学反应速率随温度变化。因此，常见的做法是在实验室、在恒温下研究反应的反应速率（等温地），这样可以消除一个变量。

Pressure and Volume. Pressure is important in a kinetic consideration of gas phase reactions. Usually, volume is fixed by running the reaction in container of fixed dimensions. For solid and liquid state reactions, pressure is usually atmospheric, and the volume of the reacting system is relatively unimportant because there is little change in volume.

压力与体积。压力是气相反应动力学的一个重要的影响因素。通常在固定尺寸的容器中反应时，反应体积是固定的。对于固体和液体反应，压力通常是大气压，反应体系的体积是相对不重要的，由于反应前后它的体积变化很小。Concentration.At any particular temperature, the rates of most chemical reactions are functions of the concentrations of one or more of the components of the system. In practice, it is usually the concentration of the reactants that are used in determining the overall rates of reaction.

浓度。在任何特定的温度下，大部分化学反应的速率是体系中一个或者多个组分的浓度的函数。实际上，一般正是反应物的浓度用以测定反应的总速度。Catalyst.Any substance that affects the rate of a chemical reaction but cannot be identified as a product or reactant is said to be a catalyst. Catalyst may accelerate the rate, but we usually refer to decelerating catalysts as inhibitors.

催化剂。影响化学反应速率，但既不是产物，也不是反应物的物质称为催化剂。催化剂可以加快反应速率，但是，通常，我们把减慢反应速率的催化剂称为抑制剂。

The order of a chemical reaction is given by the number of atomic or molecular species whose concentrations directly determine the reaction rate.

化学反应级数是浓度直接影响反应速率的原子或分子物种的数目。

The rate of hydrolysis of acetate in water is directly proportional to the ethyl acetate concentration, the reaction is said to be first order.

水中醋酸盐的水解率与乙酸乙酯的浓度成正比，所以说，反应是一级反应。

厦门大学化学化工学院

厦门大学化学化工学院 作业20090916 A类 1. ACT p.55-56: 2.12, 2.13, 2.14 2. MAC p.98: 2 3. You have obtained the following data for the alcohol content of a sample of blood: %C2H5OH: 0.084, 0.089, and 0.079. Calculate the 95% confidence limits for the mean assuming (a) that you know nothing about the precision of the method and (b) that on the basis of previous experience, you know that s= 0.005 % C2H5OH a nd that s is a good estimate of σ. B类 1. 阅读: MAC pp. 82-85 Statistical analysis of data. 2. 阅读How many samples do I need？(课程网站） 3．An analytical protocol exhibits a 95% confidence interval of ±0.06. If a 90% confidence limit of ±0.06 is required by regulations, could the protocol still be used? C类 1. The determination of nickel in a stainless steel specimen can be carried out gravimetrically using dimethylglyoxime as precipitation agent in a slightly alcaline solution; tartaric acid is used to mask Fe (III) which is the major interferent. The procedure is essentially composed of the following steps: The sample containing Ni is weighted and dissolved in a suitable volume of 6 mol/L (M) HCl followed by the addition of a suitable volume of 6 mol/L (M) HNO3 and boiling; ?A suitable volume of an aqueous solution of tartaric acid, the marking agent, is then added; ?A weighted amount of dimethyglyoxime, the precipitating agent, is dissolved in ethanol and a suitable volume of the resulting solution is added, followed by addition of 6 mol/L (M) NH3 until a slight excess is present; ?The precipitated is digested for a convenient time and the solution allowed to cool; ?The precipitate so formed is filtered trough a filtering crucible (previously heated at 110 o C to a constant weight) and until the washing solution is free from Cl- ion; ?The washed precipitated is dried at 110o C to a constant weight and the necessary calculations, to find out the Ni content in the analyzed sample, are performed. Try to identify the category of errors which are likely to be introduced by each of the steps above described. Based on your personal knowledge (theoretical and, hopefully, also practical) of gravimetric methods of analysis try to identify those steps introducing the most significant error. (参见厦门大学出版社《分析化学基础实验》p.125)

化学专业英语翻译1

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. 原子核中的质子数的原子称为原子序数，或质子数，卓电子数的电中性的原子也等于原子序数Z，总质量的原子是非常接近的总数量的质子和中子在原子核。这被称为质量数，这个数的原子中的中子，中子数，给出了所有的数量 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

《机械工程专业英语教程》课文翻译

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化学化工专业英语(课本内容)

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化学专业英语(修订版)翻译

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Uｎit 1 The RｏotｓoｆCｈemisｔry Ｉ．Ｃoｍpreｈensioｎ. 1。Ｃ 2. Ｂ3．D 4. C 5. B ＩI。Ｍａｋe ａsenｔeｎｃe ｏut of ｅach ｉｔem ｂy reaｒranging ｔhe wordｓin ｂracｋets. 1.Tｈｅｐuｒiｆｉcation of aｎorganｉc compounｄis usually a matter of consｉｄerａｂlｅdｉfｆicｕｌtｙ, and iｔis nｅcｅｓsaｒy to eｍploy vａrious methoｄs fｏr thｉｓpurpｏse。 2.Science is an ｅｖeｒ－iｎcｒｅasing boｄy ofａccｕｍｕlａｔed anｄ ｓｙsｔｅmatiｚed knowledｇe ａnd iｓalsｏan activｉty bｙwｈic ｈｋnowledge iｓｇenerated。 3.Lifｅ，aftｅr all, is onｌy cｈeｍistry,in faｃｔ, a sｍall example of ｃ hｅｍistry ｏbsｅｒved oｎａsｉngle munｄane pｌａnet。 4.Peoplｅaｒe made of molｅculｅｓ; sｏmｅｏf ｔhｅmｏleculｅs in p ｅople aｒe rａｔher ｓimple whｅreas otｈerｓａｒｅhｉghly compｌex。 5.Chｅｍistry ｉｓever preseｎｔin ｏｕｒｌｉves frｏm ｂｉｒtｈ tｏｄeａthｂeｃａｕse withoｕt chｅmｉｓtrｙｔhere iｓneither life nor deａth. 6.Maｔhｅｍaｔics apｐeａｒs ｔo be almost as humaｎkiｎｄand ａｌ ｓo ｐermeaｔeｓall aspeｃts of ｈuman life, aｌthough ｍａｎｙof us are ｎｏｔfuｌly ａwａrｅoｆtｈis. III。Tｒanｓlatioｎ. 1.（a)chｅmicaｌprｏcess (b) natuｒal scienｃe（c）the teｃhｎｉ ｑｕe of distｉllaｔioｎ 2.Iｔｉs theａtｏｍs that ｍａkｅuｐｉron, waｔeｒ，oｘygen and the lｉke/anｄso on／aｎｄsｏfortｈ/aｎd otherｗiｓe. 3.Cheｍisｔｒy haｓa very long hｉｓtorｙ, ｉnｆaｃｔ，human a ｃtivity in chｅｍｉstrｙgｏes bａｃk ｔo ｐreｒecｏrｄed tｉmｅｓ/pｒedatiｎg reｃｏrded times． 4.Aｃcoｒdｉng to/Froｍthe eｖapoｒaｔion oｆwaｔeｒ，pｅople know ／reaｌized ｔｈat ｌiquidｓcａn ｔurn/bｅ/changeｉｎto gases ｕndeｒcertain conditions/circｕmsｔance／enｖironment。 5.Yoｕｍusｔknow ｔhe propｅｒtieｓｏfｔｈe materiaｌbeｆore y ｏu use it. IＶ．Ｔrａnslation 化学是三种基础自然科学之一,另外两种是物理和生物.自从宇宙大爆炸以来，化学过程持续进行,甚至地球上生命的出现可能也是化学过程的结果。人们也许认为生命是三步进化的最终结果,第一步非常快，其余两步相当慢.这三步

生物专业英语 课文翻译

教学内容： Cytoplasm: The Dynamic, Mobile Factory 细胞质：动力工厂 Most of the properties we associate with life are properties of the cytoplasm. Much of the mass of a cell consists of this semifluid substance, which is bounded on the outside by the plasma membrane. Organelles are suspended within it, supported by the filamentous network of the cytoskeleton. Dissolved in the cytoplasmic fluid are nutrients, ions, soluble proteins, and other materials needed for cell functioning. 生命的大部分特征表现在细胞质的特征上。细胞质大部分由半流体物质组成，并由细胞膜（原生质膜）包被。细胞器悬浮在其中，并由丝状的细胞骨架支撑。细胞质中溶解了大量 的营养物质，离子，可溶蛋白以及维持细胞生理需求的其它物质。 The Nucleus: Information Central（细胞核：信息中心） The eukaryotic cell nucleus is the largest organelle and houses the genetic material (DNA) on chromosomes. (In prokaryotes the hereditary material is found in the nucleoid.) The nucleus also contains one or two organelles-the nucleoli-that play a role in cell division. A pore-perforated sac called the nuclear envelope separates the nucleus and its contents from the cytoplasm. Small molecules can pass through the nuclear envelope, but larger molecules such as mRNA and ribosomes must enter and exit via the pores. 真核细胞的细胞核是最大的细胞器，细胞核对染色体组有保护作用（原核细胞的遗传物质 存在于拟核中）。细胞核含有一或二个核仁，核仁促进细胞分裂。核膜贯穿许多小孔，小 分子可以自由通过核膜，而象mRNA和核糖体等大分子必须通过核孔运输。 Organelles: Specialized Work Units（细胞器：特殊的功能单位） All eukaryotic cells contain most of the various kinds of organelles, and each organelle performs a specialized function in the cell. Organelles described in this section include ribosomes, the endoplasmic reticulum, the Golgi complex, vacuoles, lysosomes, mitochondria, and the plastids of plant cells. 所有的真核细胞都含有多种细胞器，每个细胞器都有其特定功能。本节主要介绍核糖体， 内质网，高尔基体系，液泡，溶酶体，线粒体和植物细胞中的质体。 The number of ribosomes within a cell may range from a few hundred to many thousands. This quantity reflects the fact that, ribosomes are the sites at which amino acids are assembled into proteins for export or for use in cell processes. A complete ribosome is composed of one larger and one smaller subunit. During protein synthesis the two subunits move along a strand of mRNA, "reading" the genetic sequence coded in it and translating that sequence into protein. Several ribosomes may become attached to a single mRNA strand; such a combination is called a polysome. Most cellular proteins are manufactured on ribosomes in the cytoplasm. Exportable proteins and membrane proteins are usually made in association with the endoplasmic reticulum. 核糖体的数量变化从几百到几千，核糖体是氨基酸组装成蛋白质的重要场所。完整的核 糖体由大亚基和小亚基组成。核糖体沿着mRNA移动并阅读遗传密码，翻译成蛋白质。一条mRNA上可能有多个核糖体，称多聚核糖体。大多数细胞蛋白是由细胞质中核糖体生产。输出蛋白和膜蛋白通常与内质网有关。 The endoplasmic reticulum, a lacy array of membranous sacs, tubules, and vesicles, may be either rough (RER) or smooth (SER). Both types play roles in the synthesis and transport of proteins. The RER, which is studded with polysomes, also seems to be the source of the