3 Part One. The Predicate

Oxidation and Reduction
Generally speaking, the simple meanings of these terms are that oxidation is the addition of oxygen to a substance and reduction is the removal of oxygen. Needless to say, hydrogen seems to be the chemical opposite of oxygen (the two elements combine readily, and are evolved at opposite electrodcs during electrolysis). Removal of hydrogen is, therefore, similar to the addition of oxygen, and addition of hydrogen is similar to the removal of oxygen. Fuller meanings of the two terms are therefore: Oxidation is the addition of oxygen to, or removal of hydrogen from, a substance. Reduction is the removal of oxygen from, or addition o f hydrogen to, a substance.

2SO₂ + O₂ = 2SO₃ (oxidation of SO₂; addition of oxygen)

PbO + H₂ → Pb + H₂O (reduction of PbO; removal of oxygen)

Cl₂ + H₂ → 2HCl (reduction of Cl₂; addition of hydrogen)

H₂S + Cl: → ↓ Si + 2HCI (oxidation of H₂S; removal of hydrogen)
The terms now are applied to reactions in which neither oxygen nor hydrogen are involved. To take an example, the changc o f ferrous oxide to ferric oxide is, obviously, an oxidation; similarly, We can regard the changc of any ferrous compound to a ferric compound as an oxidation (and a changc of ferric to ferrous as a reduction): 4FeO + O₂ → 2Fe₂O₃;. FeCl₂ + Cl₂ → 2FeCl₃ Note that the valency of the metal increases during oxidation.

Metals and hydrogen form positive ions (c. g., Na⁺ and H⁺) and are, therefore, called electropositivc. Non-metals and acid radicals are electronegative as they form negative ions (c. g., O^2-, SO^2-)- Putting it another way, more complete definitions of the two terms are:

Oxidation is the addition of any electroncgativc element or radical to, or removal of any electropositivc element or radical from, a substance. Reduction is the opposite.

An oxidizing agent is a substance which brings about oxidation, a reducing agent is a substance which brings about reduction.

Oxidizing agents includc: oxygen, hydrogen peroxide, nitric acid, sulphuric acid, chlorine, potassium permanganate, potassium dichromatc.

Reducing agents includc: hydrogen, carbon, carbon monoxide, sulphur dioxide, hydrogen sulphide, ammonia, and most metals and non-metals. The equations for the oxidation o f ferrous chloridc are:

2FeCl₂ + Cl₂ → 2FeCl₃;

ionically: 2Fe²⁺ + Cl₂ → 2Fe³⁺ + 2C1^-

As already mentioned, the oxidation involves a changc of ferrous ion to ferric, it occurs by loss of an electron (c). And oxidation of chlorine to chloridc ions takes place by gain of electrons:

Fe²⁺ — e → Fe³⁺ (oxidation);

Cl₂ + 2e → 2C1^- (reduction).

To summarize, oxidation is the removal of electrons from a substance. Reduction is the addition of electrons to a substance.

An oxidizing agent is a substance that accepts electrons. A reducing agent is a substance that supplies electrons.(Remember the word ORE — Oxidation is Removal o f Electrons.)
Words and Word-Combinations to Be Memorized

agent, e. g., evolve, generally speaking, loss, meaning, monoxide, needless to say, neither... nor, non-metal, opposite, permanganate, peroxide, put into operation, put into pracitce, put it (in) another way, put off, removal, remove, say nothing of, seem, summarize

Ex. 5. Give the Uzbek equivalents for the following:

the meaning of the term, needless to say, combinc readily, a fuller meaning, add to, remove from, apply to, take an example, obviously, regard as, be the opposite, bring about oxidation, involve a change, by gain of electrons, by loss of electrons, accept, supply

Ex. 6. Give the English equivalents for the following:

Umuman olganda, ulanish oson, elektrodga ajralib chiqish, reaktsiyaga o'xshash, shuning uchun reaktsiyaga murojaat qiling, na ... va ..., masalan, shunga o'xshash tarzda, biz valentlikni oshiramiz, boshqacha qilib aytganda, to'liq aniqlash, nitrat kislota, sulfid vodorod, ammiak, metall bo'lmaganlarning aksariyati, yuqorida aytib o'tilganidek, elektronni olib tashlash, oksidlovchi, qaytaruvchi vosita

Ex. 7. Fill in the blanks with articles where necessary.

1. ... oxidation is ... removal o f ... electrons from ... substance.

2 oxidation o f... chlorine to ... chloride ions takes place b y ... gain of... electrons. 3. ... oxygen is ... oxidizing agent. 4. ... meanings o f ... terms ... oxidation and ... reduction are considered here. 5 .... change of ... ferrous oxide to ... ferric oxide is obviously ... oxidation.
Ex. 8. Give synonyms for the following:

addition, readily, therefore, full, apply, take an example, changc, obviously, regard, includc, occur, take, give

Ex. 9. Give antonyms for the following:

complex, removal, opposite, decompose, reduction, decrease, positive, metal, incomplete, exclude, loss, accept

Ex. 10. Translate the sentences into Uzbek.

1. To anticipate a little, there are several meanings o f the terms “oxidation” and “reduction”. 2. To be sure, any student can easily give an example of oxidation. 3. To begin with, one can say that the simplest meaning of the term “oxidation" is the addition of oxygen to a substance and reduction is the opposite. 4. Needless to say, this meaning is incomplete.5. To sum up, relatively little is known about the state of solid solutions or the conditions of equilibria which exist therein. 6. To mention only one, We shall consider in some detail the theory of electrolytic dissociation in its application to homogeneous equilibria. 7. Suffice it to say that similar results can be derived for other systems under investigation. 8. To put it in another way, the attraction between molecules varies inversely. 9. To tell the truth, these measurements vary so widely that it seems difficult to include them in this articlc. 10. Thorium, plutonium, mcndclcvium — not to mention uranium— belong to the actinoid series. 11. To summarize, no satisfactory equation for the process has been proposed. 12. The method is somewhat risky and not easily generalized, to say the least. 13. To put it more exactly, these values are now regarded as normal. 14. To say nothing of the details, an oxidizing agent is a substance which brings about oxidation.

15. Metals and hydrogen form positive ions, that is to say, they are electropositive. 16. To take an example, hydrogen and carbon are reducing agents. 17. To illustrate, a change of ferrous ion to ferric takes place by loss o f an electron. 18. One of the aims of education is to extend student’s views, his philosophy, so to say. 19. As emphasized above, this condition is satisfied automatically. 20. As already mentioned, We find cases where solution occurs with evolution of heat. 21. Roughly speaking, the conception of free ions affords very satisfactory explanation of all these phenomena. 22. Broadly considered, a heterogeneous system is one which consists of more than one physical state. 23. Put another way, one molecule gives rise to two smaller molecules or atoms. 24. Strictly speaking, it is for this reason that We shall to a large extent limit ourselves to a brief consideration of a gaseous state. 25. As pointed out previously, the term “oxidation” has a long histoiy. 26. As stated above, the meaning of reduction is the opposite of oxidation. 27. Generally speaking, oxidation is removal of electrons.
Ex. 11. Translate the sentences into English without using a dictionary.

1. Agar atom-molekula yoki ion o ‘zidan elektron bersa, bunday reksiyalar oksidlanish reaksiyalari deyiladi. 2. Qaytarilishish - bu qarama-qarshi jarayon. 3. Oksidlanish-qaytarilish reaksiyalari bir paytning o‘zidasodir bo‘ladi.4. Oksidlanish va qaytarilishning zamonaviy tushunchalari elektron o'tkazuvchanligi bilan bog'liq. 5. Kimyogar uchun oksidlanish bu elektronlarni yo'q qilishdir.

Ex. 12. Answer the following questions:

1. What is the meaning of the term “oxidation”? 2. In what sense ihydrogen the chemical opposite to oxygen? 3. Why is the change of any ferrous compound to a ferric compound regarded as an oxidation? 4. What is an oxidizing agent? 5. What is a reducing agent? 6. What are the most common oxidizing and reducing agents?