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INTRODUCTION

Hydrogen is a colorless, odorless and tasteless gas. Since hydrogen gas is lighter (d = 0.0899 g/L at STP) than other gas molecules, the diffusion rate of hydrogen is much greater than that of other gases.

Although hydrogen is insoluble or only slightly soluble in water and other solvents, it is soluble in palladium, iron, nickel, gold and platinum metals. Metallic palladium can absorb 900 times its volume of hydrogen.

Hydrogen forms ionic hydrides with active metals, such as potassium hydride, KH. It forms covalent compounds with nonmetals, for example HF, HC1, H20, etc. Electronegativity of hydrogen is higher than that of metals, but less than that of nonmetals.

OCCURRENCE

Hydrogen occurs in the form of free diatomic molecules (Figure 3) and its compounds. Free hydrogen occurs in nature only in negligible amounts, for example, in volcanic gases. Hydrogen gas easily escapes from earth's gravitation to enter space beyond the atmosphere. It makes up about 0.15% by mass and 15.5% by the number of atoms, of the earth's crust and atmosphere. The most important compound of hydrogen is water (H20). It is also found as a component of organic substances such as hydrocarbons, oil, coal, and natural gas. Clays and certain hydrates are common inorganic compounds which contain hydrogen.

USES

The most common uses of hydrogen are in the production of ammonia, in the hydrogenation of fats and oils and in the synthesis of methanol. Vegetable oil is converted to margarine by this process. It is also used in the refining of petroleum, the reduction of oxide ores to metals, and the production of hydrocarbons from coal.

Because of its usefulness as a rocket fuel, large quantities of hydrogen are used in the United States space programs. Tritium, one of its isotopes, is used in the production of luminous paints and in the hydrogen bomb.

Being the lightest of all gases, hydrogen was used to inflate dirigible balloons, but its high inflammability led to a number of explosions and its eventual replacement with helium.

Hydrogen is an alternative energy resource for the coming decades because it gives a lot of energy and no pollution. The only by-product is water.

SUPPLEMENTARY QUESTIONS

1. What is an isotope? Discuss the isotopes of hydrogen.

2. Explain heavy water.

3. Discuss the position of hydrogen in the periodic table.

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