In a solution of an electrolyte, it is often ncccssary to have a detailed knowledge of the spccics present. New ions or uncharged molcculcs resulting from interactions in the solution may behave quite differently from the constituent ions of the clcctrolytc. Some properties of the solutions will be profoundly affected, and the chcmist, in order to understand these phenomena, will require to know the nature of the spccics present. There arc a number of formidable difficulties in the analysis of such systems and, during the past forty years or so, a great deal of work has been done on the problem. The equilibrium properties of clcctrolytc solutions and the way in which ion-pair and complex formation can be detected and quantitatively studied arc of primary importance. Although the application of new physical and chcmical methods has produced significant contributions in this field, the information obtained from measurements of a system at equilibrium is to some extent limited, and in studying the phenomenon it is desirable to know the relevant kinetic parameters. Without this understanding, it is sometimes impossible to sketch the actual reaction mechanism by which the system approaches equilibrium. In general, wc may regard the elucidation of the structure of an clcctrolytc solution as a difficult problem which requires as many independent lines of attack as possible.
A good deal of success in the study of molcculcs in the gas phase prompted chemists to attempt to build up theories of solutions in an analogous way. The classical theories regarded the solvent as merely providing space in which the solute particles moved and interactions between the ions and the solvent molcculcs were ncglcctcd. This D assumption can be questioned on the basis of even the most elementary electrostatic considerations.
As long ago as 1833, both Faraday and Danicll concluded that electrolysis took placc through the transport of electricity by mobile charged particles or ions which were discharged at the electrodes. These ions were produced simply by dissolving the clcctrolytc in the solvent and so the conccpt of bond-breaking in the molcculcs of clcctrolytc was first established. It is now realized that the energy required for such a proccss comes from die solvation of the ions. When the ions arc introduced into solution, they interact with solvent molcculcs and a considerable heat of solvation may be involved. In order to understand such concepts, it is necessary to have a more detailed picture of the structure of the solvent molcculcs. Although non-aqueous solutions arc of considerable interest, much of the work has been done in aqueous systems and these continue to be of paramount importance.
Words and Word-Combinations to Be Memorized
assumption, behave, conclude, considerable, a good deal of, a great deal of, dctcct, discharge, electricity, to some extent, interest, interaction, kinetic, merely, mobile, neglect, or so, parameter, primary, realize, result from, transport
Ex. 5. Give the Russian equivalents for the following:
a detailed knowledge, result from interactions, affect profoundly, during forty years or so, the equilibrium properties of solutions, producc a significant contribution, the relevant kinetic parameters, neglect some parameters, die energy comes from, be of considerable interest
Ex. 6. Give the English equivalents for the following:
взаимодействия ионов и молекул в растворе, влиять на свойства, чтобы понять эти явления, есть ряд трудностей, в течение последних сорока лет, изучать количественно, иметь первостепенное значение, получать информацию, ограничивать до некоторой степени, желательно знать, приближаться к равновесию, посредством переноса, подвижная заряженная частица, разорвать связь в молекуле, вводить в раствор, для того чтобы понять, «сводный раствор
Ex. 7. Fill in the blanks with articles where necessary.
1. Sometimes it is ncccssary to have ... detailed knowledge about... composition of... solution under test. 2. It is desirable to know... relevant kinetic parameters. 3. To understand... structure of... electrolyte solution is ... difficult problem. 4. It was concluded that... electrolysis took placc through ... transport of... electricity by ... mobile charged particles. 5. Much of... work has been done in ... aqueous systems.
Ex. 8. Give synonyms for the following:
a number of, a great deal of, do, producc, significant, information, obtain, study, actual, regard, analogous
Ex. 9. Give antonyms for the following:
present, new, uncharged, differently, with, difficult, many, move, more
Ex. 10. Translate the sentences into Russian.
1. It is often necessary to understand interactions in clectrolytc solutions. 2. Some properties of the solutions will be profoundly affected. 3. In studying the properties of a solution, it is desirable to know its composition. 4. Interactions between the ions and the solvent molecules were sometimes ncglcctcd. 5. On returning, wc shall continue our investigation. 6. Tomorrow you must finish it up. 7. In studying a foreign language, one must leam a lot of foreign words by heart. 8. You are not allowed to work in the laboratory without learning the safety instruction.
9. In the proccss of oxidation, the oxygen may be supplied by the air.
10. Solids dissolve in liquids only to a limited extent. 11. Pure water conducts the electric current hardly at all. 12. Existence of germanium was predicted by D. I. Mcndclcycv in 1871.13. Crystalline salts generally diffUsc rapidly. 14. Due to crowding during formation or to erosion after formation, crystals are seldom perfect 15. The chcmical properties of ozone arc similar to those of oxygen except for its being more active. 16. Silicon resembles carbon in forming a scries of volatile hydrides. 17. In dealing with crystals, one first encounters ions—atoms or groups of atoms carrying electrical charges. 18. Nearly all mercuric compounds sublime on being heated in the closed vessel. 19. Two elements may combine spontaneously upon being mixed or under special conditions. 20. A catalyst is defined as a substancc that will change the rate of a chcmical reaction without itself being changed. 21. Carbon burns in oxygen on strong heating. 22. In studying chcmistiy, it is ncccssary to consider the nature of all kinds of matter. 23. By changing the temperature of the reacting substanccs or by changing the concentration (mass, per unit volume), the inherent tendency to react may be incrcscd or decreased. 24. Water, a compound of hydrogen and oxygen, is widely distributed over the earth. 25. Natural radioactivity was discovered by the French physicist Henri Bccqucrcl (1851-1908) in 1896 just shortly after W. K. Roentgen's discovery of X-rays in 1895. 26. Different real gases have slightly different molar volumes. 27. The forces acting between atoms in a molcculc arc very strong, and those acting between molcculcs arc weak. 28. The heat capacity of a substancc at, say, 25°C is not necessarily the same as that measured at another temperature.
29. Covalcncy links arc those commonly met with in carbon compounds.
30. Finely divided barium sulphate has a great tendency to absorb other ions from solutions.
Ex. 11. Translate the sentences into English without using a dictionary.
1. Для анализа раствора электролита необходимо знать, какие частицы находятся в нем. 2. Ионы электролита и новые ионы, получающиеся в результате взаимодействий в растворе, ведут себя по- разному. 3. Большое внимание уделялось изучению растворов за последнее время. 4. Еще в 1833 году был сделан вывод, что электролиз происходит посредством переноса электричества подвижными заряженными частицами. 5. Как водные, так и неводные растворы представляют интерес для исследователей.
Ex. 12. Answer the following questions:
1. Why is it ncccssary to know the spccics present in solution? 2. What do the properties of clcctrolytc solutions depend on? 3. What knowledge helped chemists to build up theories of solutions? 4. What fundamental conclusion made it possible to investigate clcctrolytc solutions successfully? 5. What processes take placc in clcctrolytc solutions?
Scction II
Упр. 1. Назовите значения следующих интернациональных слов:
postulate, ionization, dissociate, equivalent, association, neutral, opposite, specific, base, conccpt, statistical, attraction, interpret, polarize, identical, potential, dielectric, deviation, ideal, mobility, approximation
Упр. 2. Проверьте, помните ли вы значения следующих слов; если ист, обратитесь к словарю:
infinite, dilution, conform, assume, decrease, increase, valid, owing to, remarkably, distribute, seek (+ инфинитив), ascribc