Benedict's solution is a common reagent in biology labs. It is used to test for reducing sugars, such as glucose and fructose. Some disaccharides, such as sucrose, will give a negative result with Benedict's reagent. In this video, we test Benedict's reagent with water, sucrose, glucose, hydrolyzed sucrose, and lemon-lime soda. The hydrolyzed sucrose was made by heating sucrose with dilute hydrochloric acid and then neutralizing the acid with sodium carbonate. To use Benedict's reagent, a small quantity is added to your sample, and then your sample is heated. A positive result is the precipitation of red cuprous oxide. As expected, the first two of these samples gave negative results while the latter three were positive. Hydrochloric acid and anhydrous sodium carbonate can be bought at pool stores. Hydrated sodium carbonate can also be obtained as washing soda at some stores. Sodium citrate can be bought as "sour salt". If you have citric acid as a food flavoring, three moles of sodium hydroxide can be used to convert it to sodium citrate. Copper sulfate pentahydrate can be bought at a hardware store to kill roots in drains. Hydrochloric acid, sodium carbonate, and copper sulfate are all toxic irritants. Wear gloves and goggles while performing this experiment. Reaction seen here: C6H12O6 (aq) + 2*Cu(2+) (aq) + 4*OH- (aq) → Cu2O (s) + C6H12O7 (aq) + 2*H2O (l)

• published: 02 Apr 2011
• views: 11134
• author: ReactionFactory