Physical and Chemical properties of water and heavy water

Water :
Water has high thermal capacity, high heat of vaporization, and hydrogen bond.

→ Angular / V -shape / bent shape
→ sp³ hybridization
→ 2 lone pair and 2 bond pairs.
Ice :
At atmospheric pressure, has hexagonal shape at very low temperature, it has cubical structure.
In polar region, in rivers, the aquatic life is surviving due to thermal isolation property of water.
Physical properties :

Amphoteric nature :
NH_{3} + H_{2}O \rightleftharpoons NH_4^+ + OH^{-}
HCl + H_{2}O \rightleftharpoons H_{3}O^{+} + OH^{-}

Autoprotolysis :
H_{2}O + H_{2}O \rightleftharpoons H_{3}O^{+} + OH^{-}
D_{2}O + D_{2}O \rightleftharpoons D_{3}O^{+} + OD^{-}

Hydrates formation :

Co - ordinated water :
CrCl₃.6H₂O
[Cr(H₂O)₆]Cl₃
[Cr(H_{2}O)_{6}]^{+3}3Cl^{-}

Hard water : Which does not give lather (foam) with soap

Soft water : Which gives lather with soap.

Hardness :
Permanent hardness : due to Cl⁻ and SO_4^{-2} of Ca and Mg
Temporary hardness : due to bicarbonates of Ca and Mg.
 
By using washing soda (Na₂CO₃.10H₂O) both temporary and permanent hardness can be removed.
Temporary hardness :
Na_{2}CO_{3} + Ca(HCO_{3})_{2} \rightarrow CaCO_{3}\downarrow + \ 2NaHCO_{3}
Permanent hardness:
Na_{2}CO_{3} + MCl_{2} \rightarrow MCO_{3}\downarrow + \ 2NaCl \ (M = Ca^{+2} \ or \ Mg^{+2} )
Na_{2}CO_{3} +MSO_{4} \rightarrow + 2Na_{2}SO_{4} + MCO_{3}\downarrow

Calgon method : (sodium hexa meta phosphate)

Mg^{+2} + Na_{2}\left[Na_{4}(PO_{3})_{6}\right]\rightarrow Na_{2}\left[Na_{2}M(PO_{3})_{6}\right] + 2Na^{+}
Ca^{+2} + Na_{2}\left[Na_{4}(PO_{3})_{6}\right]\rightarrow Na_{2}\left[Na_{2}Ca(PO_{3})_{6}\right] + 2Na^{+}

Synthetic Resin Method :

Ion Exchange Method :
↓
Cation Exchange Resin :

Ca^{+2} + 2RCOOH \rightarrow (RCOO)_{2}Ca + 2H^{+}
Mg^{+2} + 2RSO_{3}H \rightarrow (RSO_{3})_{2}Ca + 2H^{+}

Anion Exchange Resin : can be revived by using dil NaOH / Na₂CO₃
Cl^{-} + RNH_{3}OH \rightarrow RNH_{3}Cl + OH^{-}
SO_4^{-2} + 2RNH_{3}OH \rightarrow R(NH_{3})_{2}SO_{4} + 2OH^{-}

Calculation of degree of hardness of water :
Equivalents of salts of Ca and Mg are given below.

\tt Hardness \ in \ ppm = \frac{weight \ of \ salt}{mol \ wt \ of \ salt} \times \frac{100}{wt \ of \ H_{2}O \ in \ gram} \times 10^{6}

Uses of D₂O (Deuterium oxide)

• used a moderator (or) coolant in nuclear reaction
• As a traces used in reaction mechanism
• used as coolant in nuclear power plants.