practical techniques
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how is gas-liquid chromatography used to identify compounds?
• the solubility determines the retention time (time taken to reach detector) • each peak represents a substance with a particular retention time • the area under each peak is proportional to the relative amount of each substance
why is Gas-liquid chromatography often combined with mass spectrometry?
GLC is very good at separating a mixture into individual compounds, but not so good at identifying them
describe the events which occur during GLC
• sample injected into stream of inert carrier gas, which carries it through the tube over the stationary phase • the components of the mixture constantly dissolve in the stationary phase, evaporate in the mobile phase, and redissolve in the tube
describe the procedure for finding the concentration of an ion with visible spectroscopy
• use a filter to separate light into monochromatic light • pass a beam of monochromatic light through a solution of the complex • detector measures the intensity of light before and after its passed through the solution
how do you set up an electrochemical cell?
• get a strip of metal, clean with emery board and propanone • place each electrode into a beaker containing ions of that metal • create a salt bridge • connect to voltmeter
describe an experiment to measure enthalpy change of solution
-put reactants in a container, stick a thermometer and measure temperature change
list the ways you can measure the rate of a reaction
gas syringe mass balance titration colorimetry
how do you hydrolyse a protein?
heat with hot 6 molar HCl under reflux for 24 hours, neutralise ammonium salts using a base
how do you remove soluble impurities?
by adding water to an organic mixture in a separating funnel
how do you make a salt in a precipitation reaction? PFWD
pick two solutions containing the ions you need, allow the salt to precipitate out, filter, wash, dry
how do you make soluble salts using an insoluble base? DFEE
pick an acid, metal/insoluble base and dissolve filter out the excess metal evaporate some of solution off before leaving the rest to evaporate slowly
how do you make soluble salts using an alkali?
titrate an alkali against an acid using indicator evaporate
in which order should you test for ions?
carbonates -> sulfates -> halides
describe procedure for the electrolysis of an aqueous solution
use wires and clips to connect electrodes to power supply insert inert electrodes into electrolyte
name 2 ways in which the concentration of ions in solution can be measured
• colorimetry - titration (if solution is acidic or alkaline)
how do you determine the concentration of a component of an equilibrium mixture without disrupting the system?
titration (after quenching) colorimetry pH
what do you need for cracking?
collection trough with boiling tube delivery tube porcelain chips mineral wool soaked with liquid parrafin bunsen