PRE-LABORATORY ASSIGNMENT Carbohydrates 1. Draw the structures of fructose (ring structures) present in a solution at equilibrium. 2. An unknown carbohydrate showed a positive test reaction when tested with Fehling's reagent, turned red when reacted with Seliwanoff's reagent, and reacted quickly with Barfoed's reagent. What conclusions can be made about this compound? 3. What test could be used to differentiate between the compounds in each set? a. sucrose and maltose b. fructose and glucose c. lactose and glucose.