metallic oxides, oxyacids. It is an important reagent in organic chemistry. It is widely used in industry.
IV. NITROGEN PENTOXIDE
Nitrogen pentoxide may be obtained when phosphorus pentoxide is added to pure, well cooled nitric acid. The temperature rises to 60-700C. The reaction symbolized:
4 HNO3 + F4010= 2N2O5 + 4 NPO3
Nitrogen pentoxide is produced by the action of ozone or nitrogen peroxide and by the action of chlorine on
dry silver nitrate. Nitrogen pentoxide is manufactured
in the form of white crystals. Its melting point is 300 C and above this point it
decomposes. If nitrogen is rapidly heated, it explodes.
Nitrogen pentoxide reacts with water, yielding nitric acid, and hence it may be regarded as nitric anhydride.
It is indicated by means of analysis
that its emperical formula is N2O5. The vapour density and the molecular weight have not been determined, hence the molecular formula is not known.
LESSON 5
GRAMMAR: Participle
PRETEXT EXERCISES
Exercise 1. Запомните значения данных слов и словосочетаний. Переведите предложения.
1.On account of its oxidizing properties moist chlorine will bleach (отбеливать) many substances.
2.Owing to its low acidity boric acid is widely used in medicine.
3.Bromine does not unite with hydrogen in sunlight unless heated.
4.Nearly all mercuric compounds sublime at once when heated.
5.Thus sodium acts energetically with water.
6.The substance tarnishes at once in the air.
7.These factors are important enough for our understanding of the nature of the phenomenon.
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8. Owing to its properties ozone is readily distinguished (отличается) from oxygen.
9. The presence of a catalyst is not sufficient for the reaction to be started.
On account of – из-за, вследствие, по причине
At once – сразу, тотчас
Owing to – благодаря, по причине
Thus – так, таким образом
Unless – если не
Enough, sufficient – довольно, достаточно
Exercise 2. Проанализируйте и переведите группы родственных слов.
Active – activity; conduct – conductor – conductivity; react – reactive – reaction – reactivity – reactor; oxide – oxidize – oxidation – oxidizing agent – peroxide; direct – directly – direction – indirect – indirectly; lustre – lustrious; vigour – vigorous – vigorously; combine – combination; burn – burner – burning.
Exercise 3. Переведите без словаря.
Intense, chemical, formation, monatomic, conductor, chemically, reactive, mixture, halogen, phosphorus, act, hydroxide, ordinary, globe, globule, brilliant, element, energetically, ammonia.
Exercise 4. Установите начальную форму.
Found, oxidized, kept, cut, seen, forming, combines, will dissolve, evolved, burning, widely, lighter, most.
TEXT A. SODIUM
Sodium in the form of compound is widely distributed and abundant element but on account of its intense chemical activity it is never found free. Sodium is a silvery-white, lustrous metal which tarnishes at once when exposed to the air owing to the formation of a film of oxide. On account of the ease with which it is oxidized, it must be kept immersed in a liquid containing no oxygen. It is lighter than water (sp. gr. 0.93); it is soft, so that it can be cut
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with knife, and at ordinary temperature it can be moulded between the fingers. Sodium melts at 97.50 C and boils at 8800. The vapour, which is purple when seen in thick layers, has a density of 12.85 (H2= 1) indicating that it is probably almost entirely monatomic.
Sodium is a good conductor of electricity. Chemically sodium is a very reactive element. It combines vigorously with oxygen, burning readily in air with brilliant, yellow flame, and forming a mixture of the oxide and peroxide. It combines directly with the halogens and with phosphorus taking fire when heated with these elements. It also combines with hydrogen when heated to 3600. The vigour of its combination
with oxygen is such that sodium will react with most oxides liberating the element previously combined with the oxygen. Thus, it acts energetically with water, forming sodium hydroxide and hydrogen and the heat of the reaction is sufficient to melt the sodium which swims, as a globule on the surface of the water. The heat evolved is, however, not great enough to ignite the hydrogen unless large pieces of sodium will dissolve in liquid ammonia forming a blue solution.
EXERCISES AND ASSIGNMENTS
²Exercise 1. Послушайте и правильно прочитайте слова и словосочетания.
Sodium, compound, widely distributed, abundant, element, intense, silvery-white, tarnish, immerse, specific gravity, knife, to mould, finger, purple, indicate, monatomic, entirely, brilliant, halogens, sodium hydroxide, liberating, previously, sufficient, to ignite.
Exercise 2. Найдите и выпишите из текста все обозначения цвета. До- полните сочетания прилагательными, обозначающими цвет:
_______________ solution
_______________ metal
_______________ flame
_______________ vapour
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Exercise 3. Найдите в тексте следующие слова и словосочетания:
В виде соединений, жидкость, не содержащая кислорода, удельный вес, почти полностью одноатомный, оксидная пленка, в толстых слоях, загораться, хороший проводник электричества, элемент, заранее соединенный с кислородом, на поверхности воды, жидкий аммиак.
Exercise 4. Вставьте пропущенные слова.
Widely … and … element Silvery-white, … metal Almost … monatomic
A very … element Liquid … no oxygen
The formation of the … of oxide
The element … combined with oxygen The … of the reaction
… pieces of sodium
Exercise 5. Найдите в тексте все предложения с причастиями. Определите их форму и функцию в предложении.
Exercise 6. Продолжите предложения, пользуясь информацией из текста.
Sodium is …
It tarnishes when …
It must be kept in a liquid…
It combines with oxygen forming…
It reacts with hydrogen …
Exercise 7. Выразите свое согласие или несогласие со следующими утверждениями. Используйте формулы.
1.Sodium is not a widely distributed element.
2.When exposed to the air it does not tarnish.
3.Sodium combines directly with phosphorus.
4.It must be kept immersed in a liquid containing oxygen.
5.Sodium is so soft that it can be moulded between the fingers.
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