The subject of acids and bases has long been one of the most controversial in chcmistry, and led to the development of an interesting series of theories.
In the 17th century, during the infancy of experimental chcmistry, acids and bases were defined or described on the basis of dicir behaviour. Tlius, bases were substanccs that neutralized acids, turned plant dyes blue, had a bitter taste, and had a smooth or slippery feeling to the skin.
In the 18th century, following the discovery of oxygen by Joseph Priestley, Lavoisier advanced the idea that oxygen was the acidifying principle of all acids. Thereafter, the experimental approach was largely abandoned and emphasis was placed on the composition of substanccs instead of the phcnomcnological properties. The development of the hydrogen theory of acidity and Faraday's studies of electrolytic conductancc in the early 19th ccntury led logically to the water-ion theory proposed by Arrhcnius. By this conccpt a base may be defined as any hydroxy compound which gives hydroxyl ions in water solution. Neutralization then involves the combination of hydroxyl ions with hydrogen formed by the acid, producing water and incidentally a salt. The role of solvent as an ionizing medium for acid-base reactions was emphasized. Although the theory under consideration was very useful and adequate for many reactions in aqueous solution, its many limitations soon bccamc apparent. The theory includes basic substanccs that arc not hydroxy compounds, does not provide for the amphotcrism exhibited by many oxides and salts, and limits the field of acid-basc reactions to aqueous solutions in spite of many known typical neutralization reactions in non-aqucous solutions.
These objections led to more or less conflicting theories: the protonic theory advanced by Bronstcd and Lowry in 1923 and the older solvent system advanced by Franklin in 1905 and later extended. In terms of the $ then popular protonic conccpt, a base is any substancc, molcculc, or ion, which accepts a proton.
Words and Word-Combinations to Be Memorized
acidify, acidity, adequate, amphoteric, amphotcrism, conductancc, under consideration, dye, electrolyte, extend, feel, of importance, incident, incidentally, instead of, of interest, medium, objection, plant, provide, in question, role, smooth, solvent, under study, in spite of, typical
Ex. 5. Give the Russian equivalents for the following:
lead to, an interesting theory, during the infancy, define, thus, neutralize an acid, a plant dye, a smooth feeling, advance an idea, thereafter, an experimental approach, placc emphasis, instead of, electrolytic conductancc, propose a conccpt, a hydroxy compound, producc a salt, incidentally, although, an adequate theory, bccomc apparent, exhibit amphotcrism, in spite of
Ex. 6. Give the English equivalents for the following:
ограничивать, (нс)воднын раствор, несмотря на, вести к, протонная теория, расширить систему, с точки зрения той теории, любое
вещество, принимать протон, после открытия кислорода, в основном, состав вещества, теория кислотности, в начале XIX столетия, по этом теории, роль растворителя, ионизирующая срсда, рассматриваемая шея, описать на основс поведения
Ex. 7. Fill in the blanks with articles where ncccssary.
1. In terms of... protonic conccpt,... base is... substancc which accepts ... proton. 2. The subject of... acids and bases is one of... most interesting in... chcmistry. 3. In... 18th ccntury Lavoisier advanced... idea that oxygen was the acidifying principle of all acids. 4. Following... discovery of oxygen ... emphasis was placcd on... composition of... substances. 5. Many typical neutralization reactions occur in ... nonaqueous solutions.
Ex. 8. Give the synonyms for the following:
lead to, a series of, following (the discovery), advance an idea, thereafter, a conccpt, producc, exhibit
Ex. 9. Give the antonyms for the following:
long, the most popular, before, in the early 19th ccntury, useful, extend, older
Ex. 10. Translate the sentences into Russian.
1. One of the most controversial problems in chemistry was that of acids and bases. 2. The development of the hydrogen theory of acidity and Faraday's studies of electrolytic conductance led to the water-ion theory. 3. The role of solvent as an ioinizing medium for acid-base reactions was pointed out. 4. The property in question was very useful for many reactions in aqueous solutions. 5. The theory was important, but its many limitations soon became apparent. 6. Analytical chcmistry detects, purifies, and answers the questions "What?" and "How much?". 7. A liquid solution, the occan, covers three-fourths of the earth's surface. 8. Any explosive substancc must be handled with carc. 9. Increase in pressure lessens the volume of a gas; increase in temperature increases the volume. 10. Calcium and silicon carbides are representatives of the direct union of carbon with metals and non-metals. 11. The word "chcmical purity" is connected with the thought of absencc of constituents other than the substancc in question. 12. The atomic theory was John Dalton's great contribution to the world's knowledge. 13. The most important chcmical property of oxygen is its acidity. 14. Pure sulphuric acid is a colourlcss, oily liquid about twice as heavy as water. IS. Atoms of the same element, with the same nuclear charge, but with different weights, are called isotopes of that element. 16. Science must always answer at least two questions — "What?" and "Why?". 17. No branch of scicncc is broader in its scope than chcmistry. 18. In a strict sense, no substancc is entirely insoluble. 19. The then president of the Russian Academy of Sciences was M. V. Lomonosov. 20. One solution is said to be more conccntratcd or more dilute than another. 21. Water is the most widely
distributed compound. 22. The properties of plant dyes is the problem under consideration. 23. Anodicr factor of great importance is the proper selection of reacting substanccs. 24. Let us consider the second condition. 25. Every year a great number of new discoveries arc made in chcmistry. 26. Wc consider it a step forward to develop the new technology of obtaning this material. 27. Both ways arc possible. 28. The hypothesis under study may prove to be right. 29. It is not always possible to prcdict the far-off results. 30. The data below must be taken into account in this consideration.
Ex. 11. Translate the sentences into English without using a dictionary.
1. Рассматриваемая теория весьма противоречива. 2. В XVII столетии кислоты и основания описывали только на основе их поведения. 3. Считалось, что основания — это вещества, способные нейтрализовать кислоты и обладающие рядом других характерных свойств. 4. После открытия кислорода большое внимание стали уделять составу веществ. 5. Развитие водородной теории кислотности и изучение электролитической проводимости привело к созданию теории Аррсниуса. 6. Для кислотно-основных реакций очень важна роль растворителя.
Ex. 12. Answer the following questions:
1. What substanccs were regarded as bases in the 17th century? 2. What important discoveries led to the water-ion theory? 3. What is a base according to Arrhcnius? 4. What arc die objections to the Arrhcnius theory? 5. What theory was proposed in 1923?
Section П
Упр. 1. Назовите значения следующих интернациональных слов:
classification, principle, practical, equilibrium, discussion, nomenclature, neutralize, action, demonstrate, result, activity, clcctrical, dissociation, variation, scheme
Упр. 2. Проверьте, помните ли вы значения следующих слов; если нет, обратитесь к словарю:
perhaps, involve, vast, devote, sour, taste, reverse, essential, strength, consequence, apply, be responsible for, advancc