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Description
Flashcards by joannalivesey, updated more than 1 year ago
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Created by joannalivesey
over 10 years ago
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| Question | Answer |
| Purification of an organic liquid product | 1. shake with sodium hydrogencarbonate solution to remove acidic impurities 2. separate from other immiscible liquids using a separating funnel 3. dry with anhydrous sodium sulfate 4. use simple distillation to collect the pure product |
| Redox titration involving manganate (VII) ions (used to find conc of Fe2+ ions/hydrogen peroxide) | • MnO4- is a strong oxidising agent • Over course of reaction, MnO4- is reduced to Mn2+ 1. Wash burette with potassium manganate of know concentration, and then fill burette with it 2. Use volumetric pipette to put solution of unknown concentration into conical flask 3. Add conc sulphuric acid to conical flask (NOT HCl or HNO4) and place on white tile 4. Add potassium manganate from burette to the flask, swirling constantly. Add the solution drop-wise as you approach end point- a permanent pink colour 5. Repeat until you get at least three concordant results within 0.1cm3 of each other |
| Heating under reflux | 1. boil liquid in pear-shaped flask attached to an upright condenser 2. add anti-bumping granules to flask to stop liquid boiling over • increases rate of reaction, allows boiling for a long time , stops loss of volatile products and reactants, stops liquids catching fire |
| Thin layer chromatography (TLC) | • spot any mixtures and reference sample on a pencil line 1cm from bottom of t.l.c. plate • place plate in a beaker with solvent below the pencil line and put a lid over the beaker • remove t.l.c. plate when solvent front is near (not at) the top, and allow plate to dry • locate spots using UV light, or ninhydrin for amino acids (for ninhydrin, spray and heat) • work out Rf values and compare with known compounds |
| Recrystallisation | • Removes both soluble and insoluble impurities • Use a solvent in which the substance is insoluble at low temps but v soluble at high temps 1. dissolve in a minimum amount of hot solvent 2. filter to remove insoluble impurities from solution 3. leave solution to cool until crystals form (soluble impurities will stay in solution) 4. collect crystals by vacuum filtration 5. wash with a minimum amount of cold solvent 6. dry in air |
| Colorimetry | 1. choose suitable filter/set wavelength 2. make up standard solutions of coloured solution 3. zero colorimeter with tube of water/solvent 4. measure absorbance of standard solutions 5. plot calibration curve 6. measure absorbance of unknown 7. read off concentration from calibration curve |
| Gas–liquid chromatography | • mobile phase is an inert carrier gas (e.g. nitrogen) • stationary phase is a high bp liquid coated on surface of finely divided solid particles • this material is packed inside a column, which is coiled inside an oven • emerging compounds are detected (sometimes by mass spectrometer) and a peak is recorded on a chromatogram • the area under each peak is proportional to amount of that component in the mixture • the time taken to emerge is called the retention time- the shorter the retention time, the higher the affinity for the mobile phase |
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