Which of the following cannot be separated by Crystallization ?

The correct option is Solution of methyl alcohol and potassium permanganate.

Step-by-Step Explanation:

1. Understanding Crystallization:
Crystallization is a physical purification technique used to separate a pure solid in the form of its crystals from a solution or impure mixture. It works effectively for solids that dissolve in a liquid medium (or solid mixtures where solubility varies significantly with temperature).

2. Analyzing the Options:

• Harvesting salt from impure sample: Salt (sodium chloride) is a solid solute dissolved in water. It can be purified and separated through crystallization.
• Separation of Alum from impure sample: Alum is a soluble solid compound that easily forms pure crystals upon cooling a saturated solution.
• Mixture of Zinc chloride and Lead (II) chloride: These are solid salts with vastly different solubilities in water at room temperature versus hot water, allowing fractional crystallization to separate them.
• Solution of methyl alcohol and potassium permanganate: Methyl alcohol (methanol) is a volatile liquid, while potassium permanganate is a solid dissolved in it. Liquid-liquid or volatile solvent-solid separation where the liquid component needs to be collected/separated relies on methods like fractional distillation, simple distillation, or evaporation rather than standard crystallization for component isolation.

Therefore, a solution of methyl alcohol and potassium permanganate cannot be appropriately separated using crystallization.