Dehydrating Sucrose (Demonstration)
(References: Shakhashiri, B.Z. Chemical Demonstrations: A Handbook for Teachers of Chemistry; Vol. 1: The University of Wisconsin Press: Madison, WI, 1983; Summerlin, L.R. and Ealy, J.L. Jr. Chemical Demonstrations: A Sourcebook for Teachers; Vol. 1: American Chemical Society: Washington, DC, 1988.)
 

Organic Chemistry  :  Hygroscopic  :  Chemical Reaction  :  Exothermic
 

Purpose:
Illustrate the hygroscopic nature of sulfuric acid as it extracts water from sugar leaving behind just the carbon backbone
 

Safety:
Wear chemical-resistant apron, gloves and a splash face shield.
Do not handle carbon product, it will contain unreacted sulfuric acid.  Neutralize with sodium bicarbonate.
Steam produced may cause burns, do not stand over vessel or inhale steam produced.
 

Materials:
10 g sucrose
50 mL beaker
1 mL water
10 mL concentrated sulfuric acid
 

Procedure:
Place 10g sucrose in a 50 mL beaker
Add 1 mL water and stir.
Pour 10 mL concentrated sulfuric acid onto the mixture, stir briskly
Step back and watch
 

Explanation:
Sulfuric acid extracts water from sugar mixture, including the glucose molecule itself.  In turn only the carbon backbone of the glucose molecules remain, thus the black “snake” of charcoal.
 

Clean-up:
When reaction is complete and vessel is cool, remove carbon product using tongs and sprinkle with sodium bicarbonate.  Then rinse thoroughly and place in a plastic bag, then put into trash.
 
 

Ginger Chateauneuf, 2000.
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