ntroduction

Concentrated sulfuric acid dehydrates common table sugar (sucrose), leaving a column of carbon

C12H22O11(s) + 11H2SO4 → 12C(s) + 11H2SO4 • H2O(l)

To Conduct Demonstration

  1. Pour sugar into any size beaker (depending on the size of the room) to a depth of 1”.
  2. Place beaker on a heat insulating mat.
  3. Pour a layer of concentrated sulfuric acid ½” to ¾” thick on top of the sugar.
  4. Place 4 liter beaker over the small beaker containing the sugar with part of the beaker extending off the mat and over the vent in the bench.  This will allow the vent to draw the  smoke and vapors produced out of the beaker, enabling the students to watch the reaction without releasing the smoke into the room.
  5. After approximately 3 to 5 minutes, the sugar will turn black and the mixture will become very hot.  A column of carbon will rise out of the beaker to a height of several inches. 

Demo Time: ~10 minutes

Safety 

Sulfuric acid is viscous and very caustic.  Gloves and goggles should be worn.  Unpleasant fumes are given off by this reaction, and it should be performed only in a large, well-ventilated room, with bench vents, preferably at the end of class.  At the end of class, push the beaker completely onto the mat so that it closes over the beaker and seals off the fumes from escaping during transport.  Carefully move the mat to a cart and then to the hood in the demo room.

Acknowledgment

Lora Ruffin and Michael Polk, Summer 2009