A student is given an aqueous mixture containing copper(II) sulfate along with a small amount of insoluble sand (silicon dioxide).
Which of the following procedures is the most suitable to obtain pure, large crystals of hydrated copper(II) sulfate, CuSO4⋅5H2O\text{CuSO}_4\cdot5\text{H}_2\text{O}CuSO4⋅5H2O, from this mixture?
Filter the mixture to remove the sand. Heat the filtrate to dryness over a hot Bunsen burner flame to evaporate all water, and collect the resulting powder.
Filter the mixture to remove the sand. Heat the filtrate gently until a saturated solution is formed, allow it to cool slowly, filter off the crystals, wash with a small volume of cold distilled water, and dry them between filter papers.
Cool the mixture rapidly in an ice bath to crystallise the copper(II) sulfate, filter the entire mixture to collect the solid residue, wash with hot distilled water, and dry in a hot oven.
Heat the mixture to dryness to evaporate all water, add ethanol to dissolve the copper(II) sulfate while leaving the sand, filter the mixture, and evaporate the ethanol filtrate to dryness.
