VIII. Fill in the blanks with the words given in the box. Translate the sentences into Russian.

Nouns	Adjectives	Verbs
colour form outlet solids	commercial complete hydrochloric spherical	to dissolve to involve to react to redden

1. If we … some hydrogen chloride in water the solution has a sour taste, … blue litmus, … with zinc.

2. When all the sodium chloride in the flask has been transformed, the reaction is… .

3. The upper … funnel of the Kipp’s apparatus contains the solution of … acid.

4. Hydrogen formed comes out through the … of the Kipp gas generator.

5. Salts are … at room temperature.

6. Crystals of salts vary in … and … .

7. There are some laboratory and … methods by which salts may be prepared.

8. Most methods to make salts … double replacement reactions.

IX. Answer the questions on the text and discuss some aspects of experiments in chemistry.

1. Why do chemists conduct experiments in the laboratory?

2. How is hydrogen chloride prepared in the laboratory? Represent this reaction by the equation.

3. How can we define that hydrogen chloride is produced? What are the main characteristics of the hydrogen chloride (smell, colour, solubility, weight)?

4. Is it possible to turn hydrogen chloride into a solution of hydrochloric acid? How? What is necessary to do? Is it possible to represent it by the equation?

5. What is chemical mechanism of obtaining hydrogen in the laboratory? Express this explanation in the equation.

6. Give the general description of the Kipp gas generator also used in the preparation of hydrogen.

7. What does the word “salt” denote?

8. What are the main characteristics of salts (smell, colour, solubility, weight)?

9. What methods of preparing salts exist in chemistry?

10. Give an example or describe in details the preparation of salts.

X. 1) Look through this text and find the answer to the question “What substances influence the course of chemical reaction?”

2) Read carefully the text where you can get additional information about experiments. Study some new information about the substances, which influence the course of chemical reaction, and be ready to discuss their properties (see questions below).

Hundreds years ago a chemist carefully put a platinum wire into a container containing a mixture of hydrogen and oxygen. The result was extraordinary. The container filled up with fog, that is, with water vapour. The temperature and pressure remained unchanged, but the reaction between hydrogen and oxygen occurred in a few seconds. Besides, the platinum wire which had caused the two gases to combine instantly, had undergone absolutely no change. Its apperance, chemical composition and weight were exactly the same after the experiment.

This experiment was done by a serious investigator, the German chemist Dobereiner. The phenomenon he observed is now called catalysis. Substances capable of making reactions to occur faster are called catalysts. Catalysts are very numerous. They may be metals – solid or powdered, oxides of great variety of elements, salts or bases. They may be used in the pure form or as mixtures.

Not every substance can accelerate any particular process. Therefore chemists say that catalysts are selective in their action: they may influence one reaction vigorously without paying attention to another. Of course, there are exceptions to this rule. For example, alluminium oxide is capable of catalyzing several dozen different synthesis reactions of both organic and inorganic compounds. Finally, different catalysts may make a mixture of the same substances react differently to form different products.

There are substances with no less surprising properties, called promoters. They do not influence the course of the reaction, neither accelerating nor decelerating it. But if added to a catalyst, they accelerate the reaction to a much greater degree than the catalyst itself. A platinum wire with “impurities” of iron, alluminium, or silicon dioxide, would cause a still more impressive effect in a mixture of hydrogen and oxygen.

There are also anticatalysis and anticatalysts. Scientists called them inhibitors. Their purpose is to slow down rapid chemical reactions.

Questions for discussion:

1. What are the substances which influence the course of chemical reactions?

2. What does the author of the text tell about catalysts?

3. What catalysts do you know?

4. What catalysts do you usually use in University laboratories on conducting experiments?

5. What the substances have the opposite effect on the course of chemical reactions (in comparison with catalysts)?

6. Do you have an experience in applying inhibitors?

7. Is it possible or necessary to use catalysts (or inhibitors) in the experiments described in the topical texts?