WATER ON EARTH

Water is an important item in our universe. We need water for transport (lakes and oceans), Generation of power, (hydroelectricity), drinking industrial processes, manufacturing and cooling among others.

Very little of the world’s water is fresh (2.6%).

Most of it (97.4%) is in oceans.

Most of the fresh water is frozen (76%). Only a tiny fraction is available for human use, about 0.01%.

Combustion of Hydrogen

Hydrogen burns in oxygen or air to form water.

2 H₂ + O₂ 2 H₂ O

Oxygen will also burn in hydrogen. Hydrogen does not itself support combustion, as may be shown by passing a lighted taper into an inverted jar of hydrogen, when the taper is extinguished.

A mixture of hydrogen with oxygen or air explodes violently when kindled, provided either gas is not present in too large excess.

Reaction with Non-Metals

Hydrogen readily combines with fluorine and chlorine, less readily with bromine, iodine, sulphur, phosphorous, nitrogen, and carbon.

H₂ + F₂ 2 HF

Hydrogen burns in chlorine gas and a mixture of hydrogen and chlorine explodes violently when kindled or exposed to bright sunlight.

H₂ + Cl₂ 2 HCl

Hydrogen combines with nitrogen on sparking or in presence of a catalyst, forming ammonia.

N₂ + 3 H₂ 2 NH₂

Reducing Properties

When hydrogen is passed over many heated metallic oxides (e.g. copper oxide, iron oxide, or lead oxide), they are reduced to the metals.

In this arrangement, dry hydrogen is passed over heated copper (II) oxide.

The copper oxide is reduced to red brown copper metal, while hydrogen oxidizes to water.

Uses

Hydrogen is used;

1. In the reduction of oxide ores,
2. In the refining of petroleum,
3. In the production of hydrocarbons from coal,
4. To fill balloons and airships, as it are the least dense gas known (i.e. it is lighter than air).

Previously, coal gas was often used for the same purpose, as it contains a high percentage of hydrogen.

However, because the flammable nature of hydrogen makes it dangerous for such use, this use of hydrogen has been to replace by helium,

1. In the Synthesis of ammonia,
2. As a fuel in Oxy-Hydrogen blowpipes,
3. For the hardening of vegetable or animal oils (i.e. to convert them into saturated fats which are solids), and
4. For the hydrogenating petroleum fractions, coal and other organic compounds.

Principal Compounds of hydrogen

Hydrogen is widely distributed in industrially important compounds and is present

In a wide range of inorganic compounds, including

1. Ammonia
2. Hydrogen Sulphide
3. Water

In the strong acids, including

1. Sulphuric Acid
2. Nitric Acid
3. Hydrochloric Acid
4. Hydrobromic Acid
5. Hydrofluoric Acid

In almost all organic compounds.

1. Alkanes
2. Alkenes
3. Alkynes
4. Alcohols