Q1: During crystallisation, formation of crystal can occur in __________ solution only.

ANS:B - supersaturated

During crystallization, the formation of crystals can occur in saturated and supersaturated solutions.

• In a saturated solution, the solution contains the maximum amount of solute that can dissolve at a given temperature. Crystals may form due to changes in temperature or other factors that disrupt the equilibrium between dissolved and undissolved solute.
• In a supersaturated solution, the concentration of the solute exceeds its equilibrium solubility. This can occur by cooling a solution that was previously heated and fully dissolved, causing more solute to remain dissolved than would be in equilibrium at the lower temperature. Crystals can precipitate out of supersaturated solutions, as they are no longer stable at the higher solute concentration.

In undersaturated solutions, the concentration of the solute is less than its equilibrium solubility at the given temperature. Crystallization does not occur in undersaturated solutions because there is not enough solute present to form crystals. So, the correct answer is: all (a), (b) and (c)