Give reasons for the following:
(a) When 30 mL of ethyl alcohol and 30 mL of water are mixed, the volume of the resulting solution is more than 60 mL.
(b) Copper is conducting as such while copper sulphate is conducting only in molten state or in aqueous solution.
(a) When 30 mL of ethyl alcohol and 30 mL of water are mixed, the volume of the resulting solution is more than 60 mL.
(b) Copper is conducting as such while copper sulphate is conducting only in molten state or in aqueous solution.
Solution
(a) Ethanol molecules get between water molecules and break some hydrogen bonds; the resulting ethanol–water attractions are weaker than the original water–water attractions, so the molecules occupy more space: (positive deviation from Raoult's law).
(b) Copper is a metallic solid with free (delocalised) electrons, so it conducts in the solid state. Copper sulphate is ionic — its ions are fixed in the solid lattice and become free to move only in the molten state or in aqueous solution, which is when it conducts.
(b) Copper is a metallic solid with free (delocalised) electrons, so it conducts in the solid state. Copper sulphate is ionic — its ions are fixed in the solid lattice and become free to move only in the molten state or in aqueous solution, which is when it conducts.
CBSE Class 12 Board · 2006 · All India Compartment · Subjective