3 Part One. The Predicate

Factors Influencing the Rate of Reactions
Every chemical reaction requires some time for its complction, but some reactions are very fast and some are very slow. Reactions between ions in solution without change in oxidation state are usually extremely fast. An example is the neutralization of an acid by a base, which proceeds as fast as the solutions can be mixed. Presumably nearly every time a hydronium ion collides with a hydroxide ion reaction occurs, and the number of collisions is very great, so that there is little delay in the reaction.

The formulation of a precipitate, such as that of silver chloridc when a solution containing silver ion is mixed with a solution containing chloridc ion, may require a few scconds, to permit the ions to diffuse together to form the crystalline grains of the precipitate:

Ag⁺(aq) + Cl^-(aq) = AgCl(c).

On the other hand, ionic oxidation-reduction reactions are sometimes very slow. An example is the oxidation of a stannous ion by a ferric ion:

2Fe³⁺ + Sn²⁺ = 2Fe²⁺ + Sn⁴⁺

This reaction does not occur every time a stannous ion collides with one or two ferric ions. In order for a reaction to take place, the collision must be of such a nature that electrons can be transferred from one ion to another, and collisions that permit this electron transfer to occur may be rare.

An example of a reaction that is extremely slow at room temperature is that between hydrogen and oxygen:

2Н₂ + O₂ = 2Н₂О.

A mixture o f hydrogen and oxygen can be kept for years but we can observe no appreciable reaction taking place.

That is why it is not unusual to hear chemists speaking about the factors that determine the rate of a reaction. These are manifold. The rate depends not only upon the composition of the reacting substances, but also upon their physical form, the intimacy o f their mixture, the temperature and pressure, the concentrations o f the reactants, spccial physical circumstances such as irradiation with visible light, ultraviolet light, X-rays, neutrons, or other waves or particles, and the presence of other substances that affect the reaction but are not changed by it.

Words and Word-Combinations to Be Memorized

affect, appreciable, collidc, collision, concentration, fcnic, a few, on the other hand, influence, ion, ionic, neutralization, in order for, permit, proceed, reduction, take place, that is why, transfer, ultraviolet, unusual, visible, wave, X-rayrequire time for, oxidation state, be extremely fast, nearly every time, collide with, form the precipitate, oxidation-reduction reactions, in order for a reaction to take place, transfer electrons, observe a reaction, the intimacy of mixture, irradiation with light, ultraviolet light, affect the reaction, hydronium ion

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

reaksiya tezligiga ta'sir qiladi, oksidlanish holatini o'zgartirmasdan, kislota asos bilan neytrallanadi, eritmalar, to'qnashuvlar soniga ta'sir qiladi, masalan kumush xlorid bir necha soniya davomida ikkinchi tomondan xona haroratida vodorod va kislorod aralashmasi bilan to'qnashadi. kuzatib turing, shuning uchun ko'rinadigan yorug'lik, rentgen nurlariga bog'liq

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

1. One can give ... an example ... a reaction which may require ... a few seconds ... its completion. 2 .... the other hand, oxidation-reduction reactions are sometimes very slow. 3. An example ... a reaction that is extremely slow... room temperature is that... hydrogen and oxygen. 4. It is quite usual to hear chemists speaking ... the factors that influence ... the rate ... a'reaction. 5. The reaction rate depends ... many factors.6. Sometimes the presence ... other substances affects ... the reaction.7. Every reaction takes different time ... its completion.

Ex. 8. Translate the sentences into Uzbek, paying attention to different functions of the word order.

1. St. Petersburg University was awarded the Ordero f Lenin in 1944 and the Orderof the Red Banner of Labour in 1969.2. In arranging his ideas for the book Principles o f Chemistry Mendeleyev felt the need to bring to inorganic chemistry the same degree o f orderthat was being achieved in organic chemistry. 3. We were orderedto start the work immediately. 4. In orderfor a reaction to take place, the collision between the ions must result in the transfer of electrons from one ion to another. 5. In orderthat the reaction might occur, the reactants should be heated. 6. We must measure all the parameters in orderto summarize them in a table. 7. Crystalline compounds have their atoms arranged in a certain order.

Ex. 9. Translate the sentences into Uzbek.

1. The door was open and we could hear Prof. N giving his lecture.2. Coming up to him for the second time I found his experiment finished.3. We saw the powdcr darkcning when it was exposed to light. 4. We shall have our papers checked and then we shall be permitted to do the experimental part. 5. We all heard her saying so.Ss w c may treat the

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

electrons in the shared electron pair as belonging to both atoms. 7. We usually think of a substance as being in a certain physical state. 8. Solutions are often thought of as being liquids. 9. They watched the sugar crystals disappearing in water. 10. Lavoisier considered oxygen as being a constituent of all acids. 11. After Dalton We find the atomic theory developed rather than rejected. 12. The inertness of the noble gases is accounted for by the fact that they have all their shells completely filled.13. We had our laboratory equipped by the beginning of a new academic year. 14. We saw the solution turning blue as the reaction proceeded. 15. They observed the temperature slowly rising.

Ex. 10. Translate the sentcnccs into English.

1. Barcha kimyoviy reaksiyalar turli tezlikda sodir bo'ladi. 2. Reaksiya tezligi reaksiya qiluvchi moddalar tarkibiga va reaktsiya sharoitlariga bog'liq. 3. Reaktsiyaga ta'sir qiluvchi omillar ko'p. 4. Ular orasida, birinchi navbatda, harorat, kontsentratsiya, katalizatorlarning mavjudligi va boshqalarni qayd etish kerak. 5. Molekulyar kinetika nuqtai nazaridan harorat ta'sirini tushuntirish oson. 6. Ba'zida reaktsiya tezligi ko'p jihatdan katalizator mavjudligiga bog'liq.

Ex. 11. Answer the following questions:

1. What reactions procccd fast? 2. What reactions are usually slow?3. In what way is silver chloride formed? 4. What example of oxidation- reduction reaction can you give? 5. What factors influence the reaction rate? 6. In what way can one classify these factors?