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# Separation + purification 1. **Separating SOLID-SOLID mixtures:** 1. **Magnetic attraction** * Separates magnetic solid from non-magnetic solid 2. **Sieving** * Separates solids with different particle sizes with sieve of suitable pore size 3. **Using suitable...

# Separation + purification 1. **Separating SOLID-SOLID mixtures:** 1. **Magnetic attraction** * Separates magnetic solid from non-magnetic solid 2. **Sieving** * Separates solids with different particle sizes with sieve of suitable pore size 3. **Using suitable solvents** * Separates solid-solid mixtures in which only one solid is soluble in the solvent 4. **Sublimation** * Separates substance that sublimes on heating from substance that is stable at sublimation temp. * e.g. naphthalene, iodine sublime * **Diagram:** * Mixture of iodine and sand is heated in a flask. * The flask has a wet cloth over the opening to keep the iodine from escaping. * Solidified iodine is collected on the cloth. * Sublimate 2. **Separating SOLID-LIQUID mixtures:** 1. **Filtration** * Separates insoluble solids from liquids * **Diagram:** * Filter paper is placed in a filter funnel, which is placed above a beaker. * The mixture is poured into the filter paper. * Residue (insoluble solid) remains in the filter paper. * Filtrate (liquid) passes through the filter paper into the beaker. * Solid particles too large to pass through the pores of filter paper. * Liquid particles pass thru pores of filter paper. 2. **Evaporation to dryness** * Separates dissolved solids from its solvent by heating until all solvent is evaporated. * Some solids will decompose under strong heat. * Solid obtained may not be pure as soluble impurities may be left behind. * Solvent must have lower b.p. than dissolved solid. * **Diagram:** * A salt solution is placed in an evaporating dish, which is heated. * Water is boiled off, leaving salt as a residue. 3. **Crystallization** * Obtains pure solid from saturated solution * temp. $\uparrow$ : solubility $\uparrow$, $\downarrow$ temp. : crystallization $\downarrow$ * **Diagram:** * A solution is heated to gently heat until saturated. * When no more solute can be dissolved. * Stop heating before all solvent has evaporated, allow solution to cool and crystallize. * Filter the mixture to collect solids → if more solid needed, repeat steps 1-3. * Wash with cold distilled water to remove impurities. 3. **Separating LIQUID-LIQUID mixtures:** 1. **Separating funnel** * Separates immiscible liquids * **Diagram** * A separating funnel is used to separate oil and water, with oil on top because of its lower density. 4. **Simple distillation** * Separates pure solvent (liquid) from solution * **Diagram:** * The apparatus consists of a flask, a thermometer, a sidearm, a condenser, and a beaker * Thermometer is placed at temp = b.p. * Solution is heated, boiling chips added for smooth boiling. * Liquid boils into gas. * Gas cools in condenser and condenses to liquid (pure). * Liquid is collected as distillate in beaker. * As more liquid vaporizes, solution becomes more concentrated. * Leaving solid residue in distillation flask. 5. **Separating LIQUID-LIQUID mixtures:** 1. **Fractional distillation:** * separates miscible liquids with diff. b.p. * **Diagram:** * The apparatus consists of a flask, a fractionating column which is above a heat source, a condenser, and a beaker. * When the mixture is heated, and the solution is heated, both ethanol and water vapor rise up the fractionating column. Ethanol vapor continues to rise at b.p. of 78°C. * Water has a higher b.p. than ethanol, condenses on cool surfaces within the fractionating column. * Liquid water remains in the flask. * Liquid ethanol is collected as distillate in beakers. * **How to prove if substance is pure?** * 1 single element/compound * Pure substances have fixed m.p./b.p., not mixed w/ other substances. * Impure substances have range of m.p./b.p. * impurities $\downarrow$ m.p of solids, and $\uparrow$ b.p of liquids. 6. **Chromatography:** * Separates mixture of substances which have diff. solubilities in solvent. * Flask w/ chromatogram should be covered to minimize loss of solvent thru evaporation, for better ink separation. * Chromatography paper * Pencil line is insoluble in most solvents, ensures line does not dissolve and travel up the paper and interfere w results * Solvent below the pencil line. * \* ethanol/water * Only 1 spot seen for B: B is pure substance * D remains on start line: D is insoluble in solvent. * A contains spots at the same height as B and C * A is mixture of B and C * Retention factor * $R_f$ value: * ratio between dist. travelled by substance *dist. travelled by solvent* * $R_f = \frac{1}{2}$ * $R_f$ value is the same regardless of dist. travelled on chromatogram. * (if same solvent + temp.) 7. **ETD** * **ETD** dissolving * crystallisation medium * SOLUTE + SOLVENT = SOLUTION * substance being dissolved * Simple distillation * Pure v/s crystallisation results * in pure solid * **Diagram:** * mixture with sand and sodium chloride solution * add water to dissolve sodium chloride * filter the mixture * sand + traces of sodium chloride solution * wash w distilled water * sand * sodium chloride * Sodium chloride solution * evaporate to dryness * sodium chloride * NaCl * add a solute * Add a solution