Hydrogen

The element hydrogen occurs free in nature in comparatively small quantities. The atmosphere contains about one volume of H₂ per 15000 – 20000 volumes of air. H₂ is also present in volcanic gases. Combined hydrogen is common. Water contains 1/9 of its weight of hydrogen. Hydrogen together with O₂ is one of the main constituents of animal and vegetable tissue.

Hydrogen is also present in nearly all organic compounds and in many gases. For general laboratory work hydrogen is prepared by the action of dilute hydrochloric acid or sulfuric acid on granulated zinc. The most important industrial method for making hydrogen is extracting from water gas by electrolysis.

Hydrogen is a colourless gas, tasteless and odourless. It is combustible, but non-supporter of combustion. Its specific gravity is very low in comparison with air being only 0.08987 gr per litre. Hydrogen was once used as the standard for the atomic weights since it is the lightest element known. It is not poisonous. The critical temperature for hydrogen is 239 °C, it is a very difficultly liquefiable gas. The liquid hydrogen is clear and colourless, resembling water. It solidifies when a liquid is evapourated in a partial vacuum. The white solid is crystalline.

Hydrogen doesn’t react at room temperature in the absence of catalysts. Hydrogen combines with many non-metals, but doesn’t react with metals at all. The readiness with which hydrogen will combine with oxygen and certain other non-metals makes it able to remove oxygen and chlorine from their compounds with the other elements. Thus, when hydrogen is passed over hot ferric oxide, lead oxide, nickel oxide, etc., hydrogen combined with the oxygen of the oxide leaves behind the metal. In these experiments hydrogen is oxidized and the metallic oxide is reduced or dioxidized. At present hydrogen is employed in the manufacture of synthetic ammonia, for hydrogenation of oils. Large quantities are also used for filling balloons and airships. It is still employed for fusing quartz and silica, for melting platinum, for autogenous soldering of lead and so on.

3. Answer the questions:

1. Does hydrogen occur free in nature in large quantities?

2. Where is hydrogen present?

3. What is the most important industrial method for making hydrogen?

4. What kind of gas is hydrogen?

5. Does hydrogen support combustion?

6. What metals does hydrogen react with?

7. Where is hydrogen applied nowadays?

4. Complete the following sentences using some active words and word combinations (see below):

1. Hydrogen…… in nearly all organic compounds and in many gases.

2. Water ……… hydrogen.

3. Hydrogen is………… …………

4. Hydrogen supports ………… …………

5. The liquid hydrogen is………… and …………

6. Hydrogen doesn’t react with …………

7. Hydrogen is………… for hydrogenation of oils.

Colourless, used, combustion, metals, combustible, occurs, clear, contains.

5. Retell the text using the scheme (see Un.1).

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