Skip to main content
UploadLanguage (EN)Support
BusinessMobileSocial MediaMarketingTechnologyArt & PhotosCareerDesignEducationPresentations & Public SpeakingGovernment & NonprofitHealthcareInternetLawLeadership & ManagementAutomotiveEngineeringSoftwareRecruiting & HRRetailSalesServicesScienceSmall Business & EntrepreneurshipFoodEnvironmentEconomy & FinanceData & AnalyticsInvestor RelationsSportsSpiritualNews & PoliticsTravelSelf ImprovementReal EstateEntertainment & HumorHealth & MedicineDevices & HardwareLifestyle
Uploaded byNellexo
DOC, PDF631 views

Cxc separation processes

The document summarizes various separation processes based on differences in properties of mixture components. It describes six common types of mixtures that can be separated: 1. Solids with different solubility separated via dissolving and filtering. 2. Liquids with different boiling points separated by simple or fractional distillation. 3. Immiscible liquids separated using a separation funnel that exploits differences in density. 4. Solids and liquids separated by filtration which exploits differences in particle size. 5. Substances separated by chromatography which exploits differences in solubility and attraction to an absorbing medium. 6. Solids where one can sublime separated by sublimation which exploits differences in sublimation temperatures.

Education◦
Download to read offline
SEE PAST PAPER QUESTIONS BELOW SUMMARY OF SEPARATION PROCESSES COMPONENTS OF THE MIXTURE TO BE SEPARATED PROPERTY IN WHICH COMPONENTS DIFFER METHOD OF SEPARATION EXAMPLES 1. Two solids one soluble and one insoluble Solubility in solvent Dissolving→Filtration→ Evaporation Add the mixture to the solvent. Filter off insoluble solid to obtain the soluble solid by evaporation of the solution. Sodium chloride and sand. 2. Two miscible liquids Boiling point Simple Distillation or fractional distillation Alcohol and water 3. Two immiscible liquids Density Floatation: Use a separation funnel i) Oil and water ii) Benzene and water iii) Mercury and water 4. Insoluble solid and liquid Size of particles Filtration Clay and water Limestone (CaCO3) and water 5. Solid or liquids Solubility in solvent and attraction to absorbing medium (Chromatography e.g. filter paper) Chromatography. Allow solvent to flow over the mixture on the filter paper i) Dyes in ink or indicators e.g. screened (Methyl, Orange) ii) Amino Acids from Protein iii) Hydrolysis products of disaccharides(complex sugars) 6. Two solids One can sublime on heating Sublimation. Heat the mixture i) Sodium Chloride and ammonium chloride ii) Iodine solid and sand. Evaporation – This is used to obtain a soluble solid (solute) from its solution. It recovers the solute from the solution by evaporating away the solvent, but not the solute. The liquid water evaporates to leave the solid behind since the water has a much lower boiling point than the solid. Evaporation separates based on differencesin boiling point. e.g. Copper (II) sulphate crysta1 from copper (II) sulphate solution. This method is also used to prepare soluble salts. Crystallisation: Another method of separating a dissolved solid from a solvent involves heating the solution to boil off some of the solvent. This creates a saturated solution. A saturated solution is one in which no more solid can dissolve at that temperature.The saturated solution is then cooled. The dissolved solid (solute) becomes less soluble and so cannot remain dissolved. Consequently, it crystallises out of solution. The crystals may then be separated from the saturated solution by filtration. Many salts, for example copper(II) sulfate, are separated from their solution by crystallisation FRACTIONAL DISTILLATION – This method is used to separate two or more liquids with different boiling points e.g. The fractions from crude oil (petroleum); ii) Oxygen and nitrogen from liquid air
SIMPLE DISTILLATION – This method is used to separate a volatile substance from a non-volatile substance e.g. i) pure water from sea water· ii) pure water from impure water. Or it can also be used to separate two liquids with different boiling points e.g. Ethanol (b.p 81°C) and water b.p (100°C) MAGNETIC SEPARATION – This method can be used to remove pieces of iron·(e.g. iron filings) from other non-magnetic materials. For example: sulphur powder and iron filings. Purifying a solid Type of mixture Method When used Solid/liquid Solid/solid Filtration Crystallisation Chromatography Dissolving and filtration To separate a solid from a 1iquid or solution in which it is insoluble To separate a solid from a liquid or solution in which it is soluble To separate solids from liquids when only small amounts are available To separate a solid which is soluble from a solid which is insoluble Purifying a liquid liquid/solid liquid/liquid Distillation Filtration or distillation Fractional distillation Layer separation (floatation) To separate a liquid from a soluble solid To separate a liquid from an insoluble solid To separate two miscible liquids (simple distillation gives poor separation). To separate two immiscible liquids Purifying a gas gas/gas Liquifaction Chemical absorption to separate gases when one is more easily liquified than the other to separate gases when one of them can be removed chemically It Is Important to understand what is achieved by filtration, washing, crystallization, distillation and distillation with a fractionating column. Then from acknowledge of solubilities, miscibilities and boiling points you can work out the best way to separate at mixture of chemicals. .___________________________________________________________________________________________________________________________________________________. Source: AQA PAPER 2 H - SAMPLE SET 1 Q7 ANSWERS 1. A student investigated food dyes using paper chromatography. This is the method used. 1. Put a spot of food colouring X on the start line. 2. Put spots of four separate dyes,A, B, C and D, on the start line. 3. Place the bottom of the paper in water and leave it for severalminutes. Figure 5 shows the apparatus the student used.
1.1) Write down two mistakes the student made in setting up the experiment and explain what problems one of the mistakes would cause. [2 marks] Another student set up the apparatus correctly. Figure 6 shows the student’s results. The result for dye D is not shown. Note:The solvent front is the distance travelled by the mobile phase (water) from the start line.
1.2) Calculate the Rf value of dye A Rf = distance moved by substance distance moved by solvent Give your answer to two significant figures. [3 marks] Rf value = ________________________ 1.3) Dye D has an Rf value of 0.80. Calculate the distance that dye D moved on the chromatography paper. [1 mark] Distance moved by dye D = ________________________ 1.4) Explain how the different dyes in X are separated by paper chromatography. [4 marks] _____________________________________________________________________________________________ _____________________________________________________________________________________________ _____________________________________________________________________________________________ _____________________________________________________________________________________________ _____________________________________________________________________________________________ _____________________________________________________________________________________________ _____________________________________________________________________________________________ _____________________________________________________________________________________________ _____________________________________________________________________________________________ 2. Mixtures may be separated in the laboratory in many different ways. Three different methods of separating mixtures are shown below. METHOD 1 METHOD 2 METHOD 3 a) Name each method of separation. (3 marks) (1)_______________________________________ (2) _______________________________________ (3) _______________________________________ b) Which method (1, 2 or 3) would be most suitable for obtaining water from potassium chloride solution? (1 mark) __________________________________________
c) Which method would be most suitable for removing sand from a mixture of sand and water? (1 mark) ________________________________________________________________________ d) State why Method 1 would not be suitable to separate copper(II) sulfate from copper(II) sulfate solution. (1 mark) _________________________________________________________________________ _________________________________________________________________________ 3. Drinking water has been distilled from sea water since at least 200AD when the process was described clearly by the Greek philosopher Aristotle. The distillation apparatus used to separate pure water from salt solution in the laboratory is shown below. 3. a) Name the solute in salt solution. (1 mark)_________________________________ b) Name the solvent in salt solution. (1 mark) _______________________________ c) What is solid A? Suggest its purpose. (2 marks) ________________________________________ _________________________________________________________________________________ d) What labels should be inserted at positions 6 and 7 ? (2 marks) __________________________________________________________________________________ __________________________________________________________________________________ e) Name the piece of apparatus labelled 5. (1 mark) __________________________________________________________________________________ f) What is the temperature on the thermometer when distillation is occurring? What does this suggest? (2 marks) __________________________________________________________________________________ __________________________________________________________________________________ __________________________________________________________________________________ g) What happens to the salt dissolved in the solution during this process? (1 mark) __________________________________________________________________________________ __________________________________________________________________________________
h) Distillation involves evaporation. What is meant by evaporation? Where in the apparatus does distillation take place? ___________________________________________________________________________________ (2 marks) i) Distillation involves condensation. What is meant by condensation? Where in the apparatus does condensation take place? (2 marks) ____________________________________________________________________________________ ____________________________________________________________________________________ 4. The table below contains a list of mixtures. In the right hand column, next to each mixture, write the best method for separating the mixture into its components. [8 marks] Method ofSeparation:Simple distillation, floatation, fractional distillation, sublimation, crystallization, dissolving and filtration, chromatography, magnetic separation Substance and Mixture Method ofseparation 1.Ethanol from ethanol and water 2. Salt from sea water 3. The different colours in black ink 4. Sand from a mixture sand and iron filings 5. Mercury from a mixture of water,cooking oil and mercury 6. Water from muddy water 7. Crushed diamond from a mixture sodium chloride and crushed diamond 8. Ammonium chloride from a mixture ammonium chloride and sodium chloride (b) Draw THREE labelled diagrams to show how you would carry out the separation for #5.