Separation and Purification

Separation and Purification Content Separating a Solid from a Liquid Technique Name Sample Diagram Steps Filtration 1. Pour the mixture into a filter funnel that is lined with filter paper. 2. Collect the filtrate in a conical flask 3. Collect the residue and dry it on a piece of filter paper. Evaporation to Dryness 1. Heat the solution in an evaporation dish 2. When all the liquid has been removed, all the impurities will be there Crystallization 1. Dissolve the solid in water 2. Filter to remove any insoluble impurities, collect the filtrate. 3. Heat the solution until it is saturated. 4. Leave it to cool and crystallize. 5. Filter to collect the crystals, wash with a little cold distilled water. Dry between a few sheets of filter paper Separating Solids from Solid Mixture Technique Name Sample Diagram Steps Using a Suitable solvent 1. Add the solvent and stir to dissolve the soluble solid. 2. Filter the suspension 3a. If using the filtrate, evaporate it to Dryness 3b. If using residue, wash residue with Distilled water Sublimation 1. Heat the mixture 2. The moment all of the chemical completely sublimes and deposits on the surface of the filter funnel, stop heating

Using a Magnet 1. Use a magnet and let it attract all the magnetically attractable chemical, wash off any impurities with distilled water and dry with sheets of filter paper Separating a Liquid from a Solution – Simple Distillation Diagram Description 1. In the distillation flask, the solution boils. Boiling chips ensure smooth boiling. The liquid vaporizes, rises, and enters the Liebig condenser 2. In the Liebig condenser, the vapor cools and condenses. It now changes back to a liquid and is known as a distillate. 3. The pure distillate is collected in the receiver (conical flask) Separating Liquids Technique Sample Diagram Steps Using a Separating Funnel 1. Pour the mixture of the two immiscible liquids into the separating funnel (Tap MUST be closed) 2. Support the separating funnel using a retort stand. Place a clean beaker below the separating funnel 3. Allow the liquids to separate completely. The denser liquid will be at the bottom layer. 4. Open the tap of the funnel to allow the bottom layer to drain into the beaker. Close the tap before the top layer of liquid runs out. 5. Place another beaker below the funnel. Open tap to allow a little of the top layer of liquid into the beaker. Dispose the liquid Separating Liquids - Fractional Distillation Occurrences during Fractional Distillation - The liquid with the lowest boiling point will distil over first

- The vapours of liquids with higher boiling points condense along the fractionating column and fall back into the round-bottomed flask. Fractionating Column and its purpose - Attached to the round-bottomed flask and the condenser. - Many glass beads in the fractionating column provide a large surface area for vapor to condense on. An example of how Fractional Distillation works Diagram Description 1. The liquid that is boiling and the heated liquid both start to vaporize and rise up 2. The evaporating vapor is condensed in the fractionating column and falls back into the flask. 3. The other vapor that was boiling reaches the upper part of the column and distils over 4. The thermometer will show a constant temperature of the distilling liquid. 5. In the Liebig Condenser, Hot vapor cools and condenses to a distillate 6. The liquid is collected as distillate in the receiver Industrial applications to fractional distillation 1. Obtain Nitrogen, Argon and oxygen from air 2. Separate petroleum into useful fractions 3. Obtain ethanol produced by the fermentation of glucose solution. Chromatography

Definition of Chromatography - Method of separating two or more components that dissolve in the same solvent. Procedure for carrying out Paper Chromatography Diagram Description 1. Set up the apparatus as shown above 2. Remove the chromatography paper when it looks like what is on the right. and mark the solvent front with a pencil. 3. Measure the distance from the starting line to the solvent front and the distance from the starting line to the separated green spot. 4. Calculate the 𝑅𝑓 value by using this formula: 𝐷𝑖𝑠𝑡𝑎𝑛𝑐𝑒 𝑡𝑟𝑎𝑣𝑒𝑙𝑙𝑒𝑑 𝑏𝑦 𝑡ℎ𝑒 𝑠𝑝𝑜𝑡 𝐷𝑖𝑠𝑡𝑎𝑛𝑐𝑒 𝑡𝑟𝑎𝑣𝑒𝑙𝑙𝑒𝑑 𝑏𝑦 𝑡ℎ𝑒 𝑠𝑜𝑙𝑣𝑒𝑛𝑡 5. Compare the 𝑅𝑓 value of the specific spot with the data on the 𝑅𝑓 value of the chemical in the data sheet (if provided) 6. If the 𝑅𝑓 values correlate, then the spot is identified as the chemical in the data sheet Uses of Chromatography - Separate components in a sample (such as dyes in an ink, pigments in plants and amino acids) - Identify the components present in a sample (such as traces of banned substances in food) - Identify substances (such as poisons, pesticides, and drugs) - Determine the purity of a substance Locating Agents Uses of Locating agents - Colourless substances will appear as coloured spots for easier identification, such as amino acids. A compound known as Ninhydrin is used as a locating agent

Procedure Sample Diagram Procedure 1. Separate the mixture of the invisible sample using a suitable solvent. 2. Stop the chromatography before the solvent reaches the top of the paper. Dry the paper 3. Spray a locating agent 4. The locating agent reacts with each of the amino acids to form colored spots on the paper. By checking the 𝑅𝑓 value of each colored spot, we can identify the different spots on the chromatogram Determining Purity Importance of Purity 1. Impurities in drugs and medicines may cause undesirable side effects. 2. In the production of silicon chips for electronics, small amounts of impurities affect devices and make them less efficient Pure Substances For a Pure Solid, - It will have an exact and constant melting point - Impurities lower the melting point, the more impurities, the lower the melting point. - Melting with a sample containing impurities will occur over a range of temperatures For a Pure Liquid - It will have an exact boiling point - Impurities will increase the boiling point, the more amount of impurities, the higher the boiling point. - Boiling a sample which contains impurities will boil over a range of temperatures Test yourself 1. Explain all possible methods of separating i. Insoluble Solid from a Liquid ii. Solids from Solid Mixture

iii. 2 miscible liquids iv. 2 immiscible liquids 2. Briefly describe some precautions used in Fractional Distillation? 3. What are some applications of distillation? 4. What is the additional equipment used for fractional distillation? 5. Define Chromatography 6. Describe how a sample of amino acids can be separated using Thin Layer Chromatography (Paper Chromatography) 7. What are some uses of Chromatography? 8. What is the use of Locating Agents? Name one of them 9. How is the Retention factor calculated? What is its significance? 10. What is the importance of Purity? 11. Explain how to test the purity of a Solid and Liquid? 12. What will you observe when an impure Solid and Liquid is heated? 13. What is a property only pure solids and liquids have?