11 EXERCISE
Detection of Common Elements in Organic Compounds
OBJECTIVE(S)
To be able to
 detect some of the elements present in organic compounds
PROCEDURE
A. Test for Carbon and Hydrogen
Mix thoroughly in a mortar and pestle 0.5 g of sugar and 1.0 g of cupric oxide. Transfer
the mixture into a test tube and clamp the test tube in an almost horizontal position.
Cover the test tube with a stopper to which is attached at a 90°C glass tubing, its end
dipping into a small test tube containing 10 mL of lime water. After the experiment,
remove first the delivery tube from the limewater before removing the burner.
What is the change in the lime water?
- The lime water became cloudy/milky.
What causes this?
- The carbon dioxide gas from the heated sucrose and cupric oxide compound, turned
the lime water cloudy/milky. The reaction of carbon dioxide and lime water formed
calcium carbonate which caused the lime water to become cloudy since calcium
carbonate is insoluble and formed white precipitate.
What is collected at the cooler end of the reaction tube