Match each chemical mixture recovery requirement on the left with the most appropriate phy… — JAMB UTME

Match each chemical mixture recovery requirement on the left with the most appropriate physical separation technique on the right.

Separating insoluble chalk ( $\text{CaCO}_3$ ) powder suspended in an aqueous mediumFiltration
Obtaining pure hydrated copper(II) tetraoxosulfate(VI) crystals ( $\text{CuSO}_4\cdot 5\text{H}_2\text{O}$ ) from an aqueous solutionEvaporation to saturation followed by cooling
Recovering thermally stable, dry sodium chloride ( $\text{NaCl}$ ) completely from sea waterEvaporation to complete dryness
Separating potassium trioxonitrate(V) ( $\text{KNO}_3$ ) from a solution containing a soluble sodium chloride ( $\text{NaCl}$ ) impurity based on temperature-solubility dependenceFractional crystallization

Answer

Insoluble chalk suspended in water is separated by filtration. Hydrated copper(II) tetraoxosulfate(VI) crystals require evaporation to saturation followed by cooling to avoid thermal decomposition. Dry sodium chloride is recovered by evaporation to complete dryness. Potassium trioxonitrate(V) is purified from sodium chloride impurity using fractional crystallization.

Each technique is uniquely suited to the physical properties of the mixture: filtration removes insoluble suspensions; evaporation to saturation followed by cooling yields hydrated crystals without thermal decomposition; direct evaporation to dryness efficiently recovers anhydrous thermally stable salts; fractional crystallization separates multiple soluble solutes using solubility-temperature gradients.

Step-by-Step Solution

Analyze the solubility and thermal stability of each solute/mixture component.

Chalk is insoluble; hydrated copper sulfate is heat-sensitive; sodium chloride is heat-stable; potassium nitrate and sodium chloride mixture contains two soluble salts with different solubility-temperature slopes.

Physical properties determine which technique yields pure product without thermal breakdown.

Match solid-liquid heterogeneous suspensions to filtration.

Chalk powder suspended in water matches filtration.

Filtration separates undissolved solid particles from liquid filtrates.

Distinguish between thermal evaporation to dryness and crystallization for soluble salts.

Thermally stable salt (NaCl) matches evaporation to complete dryness, while hydrated salt (CuSO4·5H2O) matches evaporation to saturation followed by cooling.

Evaporating hydrated salts to dryness destroys water of crystallization, yielding anhydrous powder rather than crystals.

Match multi-solute solution separation based on temperature-dependent solubility to fractional crystallization.

Separating KNO3 from NaCl impurity matches fractional crystallization.

Cooling a hot saturated solution of both salts causes KNO3 (steep solubility rise with temperature) to crystallize out first.

Key Concept

Selection of separation techniques (filtration, evaporation, crystallization, fractional crystallization) based on solubility and thermal stability.

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