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Hydrogen

Short Answer Type

121. Write chemical reactions to show amphoteric nature of water.

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122.

Give two chemical reactions in which water acts as a reducing agent.

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123.

Give two points to distinguish between fresh tap water and distilled water.

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124.

Water has some air dissolved in it. What is its significance?

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Long Answer Type

125.
What properties of water make it useful as a solvent? What type of compounds can it: (i) dissolve and (ii) hydrolyse?

Water is a universal or ideal solvent because it has high dielectric constant (79.39C²/Nm²) and high dipole moment (μ = 1 . 84 D). Due to these properties, water dissolves most of the inorganic compounds and many covalent compounds. The solubility of ionic compounds in water is due to ion-dipole interaction or solvation of ions. Covalent compounds (such as alcohols, amines, urea, glucose sugar etc.) dissolve in water because such compounds form intermolecular hydrogen bonds with water.
Water can also hydrolyse many oxides, hydrides, carbides, nitrides, phosphides and other salts. In such reactions, H⁺ and OH^- ions of water interact with anions and cations respectively to form acid or base or both.