core practicals Flashcards
steps of purifying an organic liquid
- put the distillate of impure product into separating funnel
- wash the product by adding either
-sodium hydrogencarbonate solution, shaking and releasing the pressure from CO2 produced
-saturated sodium chloride solution - allow the layers to separate in the funnel, and then run and discard the aqueous layer
- run the organic layer into a clear, dry conical flask and add three spatula loads of drying agent (e.g anhyd sodium sulfate, calcium chloride) to dry the organic liquid. when dry, the organic liquid should appear clear
- carefully decant the liquid into the distillation flask
- distill to collect the pure product
what does decant mean
it means carefully pour off organic liquid leaving the drying agent in the conical flask
which layer is usually the organic layer
the layer with the lower density (upper layer)
what will sodium hydrogencarbonate do…
will neutralise any remaining reactant acid
what will sodium chloride do?
help separate the organic layer from the aqueous layer
2 factors of the drying agent
- be insoluble in the organic liquid
- not react with the organic liquid
steps of purifying an organic solid: recrystallisation
- dissolve the impure compound in a minimum volume of HOT (near boiling solvent
- HOT FILTER solution through filter paper quickly
- COOL the filtered solution by inserting beaker in ICE
- SUCTION FILTRATE with a buchner flask to separate out crystals
- wash out the crystals with distilled water
- dry the crystals between absorbent paper
why 2. HOT FILTER solution through filter paper quickly
this step will remove any insoluble impurities and hear will prevent crystals reforming during filtration
why 3.COOL the filtered solution by inserting beaker in ICE
crystals will reform but soluble impurities will remain in solution form because they are present in small quantities so the solution is not saturated with the impurities.
ICE will increase the yield of the crystals!!
why 4. SUCTION FILTRATE with a buchner flask to separate out crystals
the water pump connected to the Buchner flask reduces the pressure and speeds up the filtration
why 5. wash out the crystals with distilled water
to remove soluble impurities
during purifyng an organic solid: recrystallisation. what are some of the reasons there is a loss of yield in this process?
- crystals lost when filtering or washing
- some product stays in solution after recrystallisation
- other side reactions occuring
also if the crystals are not dried properly, the mass will be larger than expected which can lead to a percentage yield of >100%
what is steam distillation?
where steam is passed into the mixture and the product vapour is distilled off with the water and condensed
what is an advantage of steam distillation?
the product distills at a lower temp which can prevent decomposition of the product if it has a high boiling point
process of solvent extraction?
mix organic solvent and oil-water mixture in a separating funnel then separate the oil layer.
distill to separate oil from organic solvent
add anyd CaCl2 to clove oil to dry oil
decant to remove CaCl2
hazard definition
a hazard is a substance or procedure that has the potential to do hard
e.g toxic, flammable, harmful, irritant, corrosive, oxidising, carcinogenic
risk definition
this is the probability or chance that harm will result from the use of a hazardous substance or procedure
