Water Description

Water is one of the most important compound of H and is readily available of all the chemicals. About three fourth of the earth surface is covered by water. It’s very much essential for life and two third of the human body is water. Because of its high dielectric constants and polar nature, water is an excellent solvent for polar and ionic substances. Most common physical state of water is liquid; however, it exists as solid (ice) below 0^oC and gas (steam) above 100^oC. Following are the natural sources of water.

i)             Rain water: - The purest form of natural water. Although the first few showers are not very pure s these are contaminated with dissolved impurities of gaseous oxides. But afterwards rain water is quite pure.

ii)           Sea water: - the impure from of water having about 3.5% of dissolved salts i.e. saline water and thus not fit for drinking purposes and domestic use.

iii)          Surface water: - streams, river water, lack water are the most important sources of water for all purposes.

iv)          The water usually carries many soluble impurities along with insoluble impurities as suspension and in colloidal state. Therefore purification of water is essential before its use.

The purification requires following major operations

i)             It is colour less, tasteless and odour less and poor conductor or current.

ii)           F.Pt. of pure water is 0^oC and b.pt. Is 100^oC. Its maximum density is 1.0g/ml at 4^oC.

iii)          It is a polar molecular and has V shaped structure showing sp³ hybridization i.e. tetrahedral with two positions occupied by lone pair of electrons.

iv)          Because of polar character and high dielectric constant, water is a good solvent for ionic and polar species.

v)           It has the tendency to associate and exists as associated molecule. It is the H-bonding in water which gives rise to higher specific heat, latent heat of fusion and latent heat of vaporization.