Hydrogen - Result Question 8
####10. The dielectric constant of $H_2 O$ is 80 . The electrostatic force of attraction between $Na^{+}$and $Cl^{-}$will be
[1994]
(a) reduced to $1 / 40$ in water than in air
(b) reduced to $1 / 80$ in water than in air
(c) will be increased to 80 in water than in air
(d) will remain unchanged.
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Solution:
- (b) Electrostatic forces of attraction are reduced to $1 / 80$ th in water.
Dielectric constant or relative permittivity is the factor by which the electric field between the charges is decreased relative to vacuum (or air as mentioned in this question).
(b) In liquid state, the $H_2 O$ molecules are held together by intermolecular $H$-bonds.
When water freezes at atmospheric pressure it crystalises in normal hexagonal form. In it, each oxygen atom is surrounded by 4 hydrogen atoms, two by strong covalent bonds and two by weak hydrogen bonds. Since hydrogen bonds are longer than covalent bonds. The molecules of water are not closely packed in crystal lattice. There exists a number of hollow spaces in the crystal lattice, which decreases the density of ice.
