Question

For Organic chemistry lab:

Distillation:

1. If the heat source in a distillation is a heating mantle, why should it be set in a holder so it isn’t resting on the bench top? Would a stirring hot plate have to be held above the bench top? Why must the distilling flask be clamped so it cannot fall? Imagine some problem occurring that requires you to immediately remove the heat from the distilling flask. Think about this, then go back to the other two questions.

2. You don’t normally use a plastic Keep clip to hold the distilling on the rest of the setup. Why not? How hard is it to chip a melted Keck clip off a joint water flask, anyway?

Extraction:

1. In a typical “Extraction of caffeine” experiment, you use boiling water to get the caffeine out of the coffee or tea, and then extract this aqueous solution with diethyl ether or methylene chloride. Why can’t you immediately put the aqueous solution into the sep funnel with the ether or methylene chloride in order to save time?

Answer 1

Answer 1

The heating mantle is set in holder just to avoid its slippage in any odd case.

Yes, the stirring hot plate must be on the bench top because it has zero chances of slippage.

Distilling flask must be cramps so that in case of instrumental disturbances, the heat source can be replaced without disturbing the whole set up.

Answer 2

Plastic clips have chances of getting it melted during the procedure

The molten plastic sticks firmly to glass and hence, it is very difficult to remove

Extraction:

Boling water is at temperature of 100 degrees C, which far higher than boiling points of DCM and ether. Addition of ether will result in its combustion which will destroy the caffeine.