$(a)$ What separation technique will you apply for the separation of the following?
$(i)$ Ammonium chloride from sodium chloride.
$(ii)$ Different pigments from the extract of flower petals.
$(b)$ What is crystallisation? List two ways in which the crystallisation technique is better than the simple evaporation technique.

(A-D) $(i)$ Sublimation.
$(ii)$ Paper chromatography.
$(b)$ Crystallisation is a process that separates a pure solid in the form of its crystals from a solution.
The crystallisation technique is better than the simple evaporation technique because:
$1$. Some solids decompose or may get charred (e.g.,sugar) upon heating to dryness.
$2$. Some impurities may remain dissolved in the solution even after filtration; evaporation would cause these impurities to contaminate the solid,whereas crystallisation leaves them in the mother liquor.