Some Common Techniques for Separation of a Mixture

1. Some Common Techniques for Separation of a Mixture

2. 1. Decanting Separate a solid-liquid mixture based on difference in solubility or density Decant = To gently pour off a liquid without disturbing the sediment (solid)

3. 1. Decanting - continued When trying to decant and save an aqueous solution, it is often poured slowly down a stirring rod. The stirring rod acts as a pathway to direct the liquid. This method works because of the large intermolecular forces , IMFS between water molecules. The strength of the IMFs makes water molecules “sticky” – where one molecule goes the next is sure to follow. Intermolecular forces are the attractions which occur between separate molecules

4. 1. Decanting - continued Decanting would also work with two liquids of different density – but – it is easier to use a separatory funnel – a separatory funnel is sort of like “upside down” decanting

5. 2. Gravity Filtration Separate a solid-liquid mixture by differences in solubility Pour liquid – solid mixture to be separated through a filter paper the insoluble substance (unable to be dissolved) will be caught on the filter, the soluble (able to be dissolved) substances will pass through as part of the filtrate Let Gravity Do The Work!!!

6. 3. Vacuum Filtration Separate a solid-liquid mixture by differences in solubility A special side-arm (vacuum) flask, called a Büchner Flask are used together to filter a solid from solid-liquid mixture and a special type of funnel called a Büchner Funnel Let air pressure Do The Work!!!

7. 3. Vacuum Filtration –Continued The Büchner Flask is attached via a hose to a water nozzle and the water is turned on full blast! The rushing water creates a vacuum in the Büchner Funnel (Bernoulli’s Principle). The atmospheric pressure then ‘pushes’ the filtrate through the filter paper and funnel. The insoluble substance is left on the filter paper.

8. 4. Chromatography Separate a mixture based on preferential absorption of the constituents onto a paper strip.

9. Paper Chromatography Solvent Front Filter paper mixture solvent A piece of chromatography paper (the stationary phase) is ‘dotted’ with a sample of the mixture to be separated. The paper is placed into a solvent (the mobile phase) known to dissolve the sample. The paper will wick up the solvent via capillaryaction (liquid rising against gravity due to IMFs). The sample dissolves in the advancing solvent front. (c) The various constituents (parts) of the mixture move up at different rates based on their mass, size, charge, etc. Rf values are then analyzed to determine the compon- entsof the mixture

10. Paper Chromatography Chromatogram = the paper strip on which all or some of the constituents of a mixture have been separated by being adsorbed at different locations Origin= the point on the chromatography paper where the sample of the mixture is originally “dotted” Rf values = the ratio of the distance a compound moved from the origin to the distance between the origin and the solvent front Stationary Phase (chromatography paper) Stationary Phase (chromatography paper) Starting Line Ink spots are centered, and evenly spaced on the starting line. Notice that the line and ink dots must be ABOVE the liquid level in the beaker when the paper is placed in contact with the mobile phase! If it were below the liquid level, the ink would wash out into the liquid! Starting Line Ink spots are centered, and evenly spaced on the starting line. Notice that the line and ink dots must be ABOVE the liquid level in the beaker when the paper is placed in contact with the mobile phase! If it were below the liquid level, the ink would wash out into the liquid! Beaker Beaker Mobile Phase (solution of NH3, butanol and water) Mobile Phase (solution of NH3, butanol and water)

11. 5. Evaporation Separate solid-liquid mixture by differences in boiling points used to separate the constituents of a solution when the liquid portion, the solvent (thing that does the dissolving) has a much lower boiling point than that of the solid portion, the solute (thing that gets dissolved) Could also be used to separate a suspension This method is only good if there is no need to recover the solvent. Stationary Phase (chromatography paper) Stationary Phase (chromatography paper) Starting Line Ink spots are centered, and evenly spaced on the starting line. Notice that the line and ink dots must be ABOVE the liquid level in the beaker when the paper is placed in contact with the mobile phase! If it were below the liquid level, the ink would wash out into the liquid! Starting Line Ink spots are centered, and evenly spaced on the starting line. Notice that the line and ink dots must be ABOVE the liquid level in the beaker when the paper is placed in contact with the mobile phase! If it were below the liquid level, the ink would wash out into the liquid! Beaker Beaker Mobile Phase (solution of NH3, butanol and water) Mobile Phase (solution of NH3, butanol and water)

12. 6. Distillation Separate liquid-liquid or liquid-solid mixture by differences in boiling points Use when ALL the components of a mixture must be recovered - best for separation of two different liquids Stationary Phase (chromatography paper) Stationary Phase (chromatography paper) Starting Line Ink spots are centered, and evenly spaced on the starting line. Notice that the line and ink dots must be ABOVE the liquid level in the beaker when the paper is placed in contact with the mobile phase! If it were below the liquid level, the ink would wash out into the liquid! Starting Line Ink spots are centered, and evenly spaced on the starting line. Notice that the line and ink dots must be ABOVE the liquid level in the beaker when the paper is placed in contact with the mobile phase! If it were below the liquid level, the ink would wash out into the liquid! Beaker Beaker Mobile Phase (solution of NH3, butanol and water) Mobile Phase (solution of NH3, butanol and water)

13. Distillation - continued The distillate or condensate is the purified component of the mixture the distilling flask iswhere the original mixture is heated the condenser Stationary Phase (chromatography paper) Stationary Phase (chromatography paper) Starting Line Ink spots are centered, and evenly spaced on the starting line. Notice that the line and ink dots must be ABOVE the liquid level in the beaker when the paper is placed in contact with the mobile phase! If it were below the liquid level, the ink would wash out into the liquid! Starting Line Ink spots are centered, and evenly spaced on the starting line. Notice that the line and ink dots must be ABOVE the liquid level in the beaker when the paper is placed in contact with the mobile phase! If it were below the liquid level, the ink would wash out into the liquid! Beaker Beaker Mobile Phase (solution of NH3, butanol and water) Mobile Phase (solution of NH3, butanol and water)

14. 7. Magnetism Separate the components of a mixture based on differences in magnetism In a simple example, a mixture of iron filings and sulfur powder are separated from one another using a magnet. Stationary Phase (chromatography paper) Stationary Phase (chromatography paper) Starting Line Ink spots are centered, and evenly spaced on the starting line. Notice that the line and ink dots must be ABOVE the liquid level in the beaker when the paper is placed in contact with the mobile phase! If it were below the liquid level, the ink would wash out into the liquid! Starting Line Ink spots are centered, and evenly spaced on the starting line. Notice that the line and ink dots must be ABOVE the liquid level in the beaker when the paper is placed in contact with the mobile phase! If it were below the liquid level, the ink would wash out into the liquid! Beaker Beaker Mobile Phase (solution of NH3, butanol and water) Mobile Phase (solution of NH3, butanol and water)

15. Magnetism In a more complicated example, a magnet is used to bend the path of heavy and light (mass) charged particles (isotopes, molecules, molecular fragments) to separate the components of a mixture on an atomic or molecular level. The equipment used to accomplish this is called a mass spectrometer. Stationary Phase (chromatography paper) Stationary Phase (chromatography paper) Starting Line Ink spots are centered, and evenly spaced on the starting line. Notice that the line and ink dots must be ABOVE the liquid level in the beaker when the paper is placed in contact with the mobile phase! If it were below the liquid level, the ink would wash out into the liquid! Starting Line Ink spots are centered, and evenly spaced on the starting line. Notice that the line and ink dots must be ABOVE the liquid level in the beaker when the paper is placed in contact with the mobile phase! If it were below the liquid level, the ink would wash out into the liquid! Beaker Beaker Mobile Phase (solution of NH3, butanol and water) Mobile Phase (solution of NH3, butanol and water)

16. Vocab • Büchner flask • Büchner funnel • Capillary action • Chromatogram • Chromatography • Chromatography, paper • Condensate • Condenser • Component(s) • Constituent(s) • Decant(ing) • Distillate • Distillation • Distilling flask • Filtrate • Filtration • Filtration, gravity • Filtration, vacuum • Insoluble • Intermolecular forces (IMFs) • Mass spectrometer • Mobile phase • Sediment • Soluble • Solute • Solution • Solvent • Solvent front • Stationary phase • “Wick up”