Chapter 16 Flashcards
What does Quickfit Appartus include
Round bottom/pear shaped flask Condenser Receiver Screw cap adaptor Still head
How do you heat organic reactions?
They are heated ro overcome the activation energy and increase the rate of reaftion ; heating under reflux is a common procedure used to prepare an organic liquid without boiling off rhe solvent, reactants or products
Equipment needed to heat under reflux
Round bottom/pear shaped flask Condenser Rubber tubinf Stand and clamo Heat source (tripod/bunsen burner/gauze/heating mantle)
When is a water bath used when heating under reflux?
If the reaction can be carried out at less than 100 degrees celsius
Precaution taken when heating flammable liquids?
Heating mantle used so there is no naked flame present ; added level of safety should an apparatus crack
Purpose of anti-bumping granules?
To ensure that the lquid boils smoothly and if the granules are not used rhen large bubbles form at the bottom of the liquid and make the glassware vibrate/jump violently
Purpose of grease?
Applied to the ground-glass joints on the condenser so it comes apart easily at the end ; also provides a good seal by rotating it
Position of equipment when heating under reflux?
Condenser is kept upright with water coming in at the bottom and out through the top ; condenser is clamped loosely as the glass outer jacket is fragile and easily broken. NO STOPPER AT TOP OTHERWISE THERE WOULD BE A CLOSED SYSTEM AND PRESSURE WOULD BUILD UP INSIDE AS THE HEATED AIR EXPANDED - apparatus could explode
Water in the condenser?
Rubber tubing connects inlet of the condenser to the tap and outlet to the sink ; water enter condenser at the bottom and leaves at rhe rop to ensure the outer jacket is full
Purpose of heating under reflux?
Enables a liquid to be continually boiled whilst the reaction takes place - prevents volatile components from escaping and the flask boiling dry as the vapour rises unril it meets the outer jacket of cold water causing it to condense and drip back into the flask
Distillation?
Separates a pure liquid from its impurities - only works due to differences in boiling point. Many reactions may not go to completion/produce by-products as well as the desired product (crude oil needs to be purified)
How is flask in distillation?
Clamped by its neck (pear shaped) and still hesd is connected to the flask. Still head has 2 ground glass joints ; 1 to fit the screw cap adaptor and the other to fit the condenser - SHOULD BE GREASED
Where is second clamp placed in distillation?
Around the receiver adaptor where it is attached to the condenser thus no need to clamp the condenser as it is supported sufficiently at both ends
Where does water enter for distillation?
ALWAYS lowest point ; this is the closest ro receiver adaptor for distillation (inlet)
Once appartus for distillation is set up?
Flask is heated and the mixture starts ro boil - different liquids have different boiling points and most volatile liquids will boil first. They will move out if the flask, condense, become a liquid and fhen drip info the collecting flask
What else can happen when purifiying organic products?
Water may be obtained along with the product - will see two liquid layers inside collection flask ; one the organic layer and the ofher the aqueous/water layer. Easy to separate these two by adding in more water and whichever one gets bigger v aqueous
