Salt is used to clear snow on the roads covered with snow to:
Answer & explanation
Correct answer: option 1
The correct answer is Option (1) → Decrease the freezing point
A solution of a non-volatile solute freezes at a lower temperature than the pure solvent; this is the depression of freezing point, a colligative property:
\( \displaystyle \Delta T_f = i\,K_f\,m \)
When salt is spread on snow, it dissolves in the thin layer of water on the ice and forms a brine whose freezing point is well below 0 °C. At the road temperature this brine cannot stay frozen, so the snow and ice melt. NaCl gives two ions (i ≈ 2), which doubles the effect compared with a non-electrolyte.
Why the other options are incorrect
Option (2) Increase the boiling point — Incorrect. Salt does raise the boiling point, but that has nothing to do with melting snow.
Option (3) Increase the osmotic pressure — Incorrect. Osmotic pressure plays no part in melting ice on a road.
Option (4) Increase the solubility of salt — Incorrect. The salt is the solute; its solubility is not what clears the snow.