Practicals Flashcards
what should you never do when heating under reflux
put a stopper on the top of a condenser
closed system would lead to build up of pressure as heated air expands and apparatus exploding
what apparatus is needed to heat under reflux
pear shaped flask
condenser
rubber tubing
stand and clamp
heat source
why do you use anti bumping granules
to ensure that the liquid boils smoothly
why should water enter the condenser enter at the bottom and leave at the top
to ensure that the outer jacket is always full
what are the benefits to heating under reflux
enables liquid to be continually boiled whilst reaction takes place
prevents volatile components from escaping and the flask from
boiling dry
what is a common method to separate a pure liquid from its impurities
distillation
what do you need to carry out distillation
pear shaped flask
condenser
rubber tubing
heat source
stand and clamp
screw cap adaptor/thermometer pocket
receiver adaptor
still head
why is a second clamp placed around the receiver adapter at the point of jt being attached to the condenser
removed the need to clamp the condenser as it will be supported at both ends
how does distillation work
flask is heated and mixture starts to boil
the liquid which is most volatile will boil first
vapour moves out of flask and into other parts of apparatus
leaves less volatile components of mixture
when vapour reaches cold condenser, condense and became a liquid
how do you separate 2 liquids when the organic layer has been identified
using a separation funnel
how do you use a separating funnel
ensure that tap is closed
put moisture into funnel and place a stopper in the top and invert
allow layers to settle
add some water to see which layer increases in volume - aqueous layer
place conical flask under separating funnel, remove the stopper and open tap j them the whole of lower layer is left in funnel
place a second conical flask under separating funnel to collect other layer
how do you separate 2 liquids if one is an acid containing impurities
adding aqueous sodium carbonate and shaking mixture
acid will react w the sodium carbonate and release CO2
why should you bind the stoppered separating funnel upside down when CO2 is released from acid reaction with sodium carbonate (aq)
to release any gas pressure that may build up
what is used to dry an organic liquid
anhydrous inorganic salt
what is used to dry hydrocarbons
anhydrous calcium chloride
what is used for general drying
anhydrous calcium sulfate/ magnesium sulfate
what is the procedure for drying an organic liquid
add liquid to conical flask
add some drying agent using a spatula
place stopper to prevent product from evaporating away and leave for 10 mins
if solid is in a lump, as done agents until solid has dispersed in solution as a fine powder
decant liquid from solid into another flask
if an organic liquid is dry, what should it look like
clear
why might you have to carry out redistillation
when organic liquids have boiling points that are relatively close together
