The Student Room Group

Heating under reflux apparatus

1-bromobutane (boiling temperature 102oC) may be prepared from butan-1-ol (boiling temperature 117oC)

The reagents are heated under reflux at 100oC for about 45 minutes. Draw a diagram of the apparatus that you would use for this procedure. (4 marks)

Okay this is what i've done.
I've drawn the condenser, round bottomed flask, the flow of water in the condenser, shown that the top of the apparatus is open, shown that the apparatus isn't sealed, ie the condenser and the round bottomed flask are separate. Now for the heating bit, do you just use a water bath/sand bath?
Widowmaker
1-bromobutane (boiling temperature 102oC) may be prepared from butan-1-ol (boiling temperature 117oC)

The reagents are heated under reflux at 100oC for about 45 minutes. Draw a diagram of the apparatus that you would use for this procedure. (4 marks)

Okay this is what i've done.
I've drawn the condenser, round bottomed flask, the flow of water in the condenser, shown that the top of the apparatus is open, shown that the apparatus isn't sealed, ie the condenser and the round bottomed flask are separate. Now for the heating bit, do you just use a water bath/sand bath?

What do you mean by it isn't sealed? I presume you've shown theyre separate pieces of apparatus but connected via the ground glass parts.

For heating, woudn't you use a bunsen? You couldn't use a water bath due to the high temperature, but I suupose you could use a sandbath if your school considers that normal equipment. Have you got the thermometer shown in your diagram?
Golden Maverick
What do you mean by it isn't sealed? I presume you've shown theyre separate pieces of apparatus but connected via the ground glass parts.

For heating, woudn't you use a bunsen? You couldn't use a water bath due to the high temperature, but I suupose you could use a sandbath if your school considers that normal equipment. Have you got the thermometer shown in your diagram?

what? You don't need a thermometer for heating under reflux. The top part of the apparatus is open.
Widowmaker
what? You don't need a thermometer for heating under reflux. The top part of the apparatus is open.

I was thinking if you were using a bunsen you'd need a thermometer to make sure it was the correct temperature. If you were using a sandbath you wouldn't I suppose.
One option is just to indicate 'heat' on your diagram and not specify how you would heat it.
Golden Maverick
One option is just to indicate 'heat' on your diagram and not specify how you would heat it.

i tried doing that but my teacher told me i wouldn't get any marks with edexcel.
Reply 6
Don't seal the top of the condenser when heating under reflux or it will explode due to expanding air!

Don't need a thermometer as you have a temperature gradient anyway in the vertical condenser - just keep heating it steadily. I would use an oil bath on a heated magnetic stirrer - but I suppose that's not really school equipment?
oxymoron
Don't seal the top of the condenser when heating under reflux or it will explode due to expanding air!

Don't need a thermometer as you have a temperature gradient anyway in the vertical condenser - just keep heating it steadily. I would use an oil bath on a heated magnetic stirrer - but I suppose that's not really school equipment?

would a sand bath do?
Reply 8
Widowmaker
would a sand bath do?

Yes - it would, and I would go for that over a bunsen due to safety implications of naked flames with flammable vapours/liquids around.
Reply 9
The link below shows you the official sketches from Rod Beavon - the chief examiner for Edexcel Chemistry. Draw that and you get full marks (although you should probs use a ruler!)

http://www.rod.beavon.clara.net/apparatus.htm
iw ould reccomend using an electric heatin mantle since it allows for flask to be inserted and heats, so its safer and much simpler than other methods
Reply 11
use a rotary evaporator
Widowmaker
...the flow of water in the condenser, shown that the top of the apparatus is open...


I know this is a little old now but, ensure that the water inlet is at the bottome of the condenser and NOT at the top. You probably already know this but it may be of use to others who didn't know. It's definately worth a mark.
Reply 13
Dr Rod Beaven has drawn his in pen..oh dear. You lose a mark if you draw them in pen. My teachers bang it into me every lesson that they must be drawn in pencil or you'll lose a mark.
diagram in pencil

using a ruler, label it in pen
Actually, look at the, Hints for good diagrams

Draw in whatever medium you prefer.


Maybe it doesn't really matter anymore, but I'll still draw in pencil just incase I mess it up :biggrin: