3.4 Separation of Substances Flashcards
hand separation
where mechanical mixtures are separated by hand or by the use of a sieve or magnet
filtration
where mechanical mixtures involving solids and liquids are passed through a filter to separate solids from liquids or larger chunks from smaller chunks
residue
material that remains on the filter paper after the filtration method of separation is used
filtrate
liquid which passes through the filter paper after the filtration method of separation is used
evaporation
where the liquid in a solid in liquid solution (or liquid in liquid if they have very different BP) is evaporated or boiled away, leaving the solid behind
distillation
where a liquid in liquid (or solid in liquid, less common) solution is heated in a distillation setup, the liquid with the lowest BP boils first, the vapour ascends to the distillation flask, passes a thermometer, enters the side-arm of the flask and contacts the cold inner surface of the condenser, where it cools back in liquid and drops out of the condenser
distillate
the purified liquid that drops out of the condenser after the distillation method of separation is used
when are re-distillations necessary
when the liquids present have boiling temperatures which are quite close to each other
solvent extraction: solid from a mechanical mixture of solids
where a liquid is used to dissolve one or more of the solids present, but leaves others undissolved
an ideal case of solid in solid solvent extraction is…
when there are only two solids present so that the desired solid either:
- is left behind
- dissolved and may be separated with evaporation later
miscible
if two liquids are mutually soluble in each other in all proportions
immiscible
if two liquids are insoluble in each other
solvent extraction: dissolved liquid or solid from a liquid solution
where the added solvent is immiscible with the solvent already present and can dissolve the desired substances from the solution and leave the unwanted substance behind (or vice versa)
When is a separatory funnel used?
When solvents form layers in solvent extraction.
When using a separatory funnel, assume 80% if the desired substance leaves, if you repeat this process, how much will be left after three extractions?
0.20 x 0.20 x 0.20 = 0.008 = 0.8%
recrystalization
where a solid in liquid solution is separated in a pure crystalline state –> a saturated solution of a desired solid is prepared in a suitable solvent (adding a solid to a solvent at room temperature until no more solid dissolves or adding just enough hot solvent to dissolve the solid), the solvent is then allowed to slowly evaporate or cool, and as it does some desired solid comes out of the solution as crystals (SORRY GUYS, IK THIS IS SUPER LONG)
saturated solution
a solution that has dissolved all of the solid it can, all the solvent present is just enough to keep the solid dissolved
true or false: the solvent used during the recrystallization method is allowed to evaporate completely
FALSE
When is the recrystallization method most commonly used?
When the solid consists mostly of the desired material and small amounts of one or more impurities
fractional crystallization
sometimes used to describe the process of purifying a substance by recrystallization
gravity separation
where desired solids from a mechanical mixture are separated, based on their density
centrifuge
equipment that whirls a test tube around at extremely high speeds forcing finely dispersed solids to the bottom of the test tube
precipitate
solid formed in a liquid solution as a result of a chemical reaction
paper and thin layer chromatography
where a drop of solid in liquid mixture is put a near one end of a chromatography sheet and allowed to dry, another liquid (the developing solvent) is allowed to absorb into the lower end of the chromatographic sheet containing the mixture and the liquid is absorbed up the sheet, a solvent front is seen as the liquid slowly moves upwards
