4. Why do we have to keep Fehling's A separate with Fehling's B?

Introductory Chemistry For Today
8th Edition
ISBN:9781285644561
Author:Seager
Publisher:Seager
Chapter10: Radioactivity And Nuclear Processes
Section: Chapter Questions
Problem 10.68E
icon
Related questions
icon
Concept explainers
Question
4. Why do we have to keep Fehling's A separate with Fehling’s B?
Transcribed Image Text:4. Why do we have to keep Fehling's A separate with Fehling’s B?
REACTIONS OF CARBOHYDRATES
Reagents:Samples:10% glucose, galactose, fructose, xylose, maltose, sucrose, lactose, starch
(5 ml each) ,2 ml Fehling's A, 2 ml Fehling's B, 8 ml Benedict's reagent, 8 ml
Barfoed's reagent, 3 g sodium acetate, 2 g phenylhydrazineHCl
Materials: 12( 20 ml) test tubes, test tube rack, test tube brush, test tube holder, alcohol
lamp, tripod, wire gauze, water bath, (10 ml) graduated cylinder, dropper, stirring
rod, beaker(250 ml), spatula, microscope,7 glass slide, 7 cover slip, watch glass,
platform balance
Procedure:
1. Osazone formation -Mix 3 g sodium acetate and 2 g phenylhydrazineHCL and 14 ml
distilled water. Warm with stirring until solution clears.
Place 1 ml sugar solution (glucose, fructose, galactose, maltose, xylose, sucrose, lactose)
in separate tube. Add 2 ml of the hot solution in each of the sugar solution, stopper with
cotton, mix well and heat in a boiling water bath for 30 minutes. Cool at room
temperature and examine the crystals under the microscope. Draw and compare the
crystals.
2. Fehling's test – mix 2 ml Fehling's A with 2 ml Fehling's B and add 4 ml of water. Boil
the solution for 1 minute. If the solution remains clear blue, place 1 ml of the solution in 8
separate test tubes. Add 5 drops of the sugar solution (glucose, fructose, galactose, xylose,
maltose, lactose, sucrose, starch)in separate test tubes. Place the tubes in a boiling water
bath for another 2 minutes and note the formation and color of precipitate.
3. Benedict's test – place 1 ml of Benedict's reagent in 8 separate test tubes. Add 5 drops of
the sugar solution (use all 8 samples) in separate tubes. Place in a boiling water bath for 2
minutes. Cool and observe formation and color of precipitate.
4. Barfoed's test – place 1 ml Barfoed's reagent in 8 separate tubes. Add 5 drops of the
sugar solution (use all 8 samples) in separate tubes. Place in a boiling water bath for 5
minutes. Cool and observe formation and color of precipitate.
Transcribed Image Text:REACTIONS OF CARBOHYDRATES Reagents:Samples:10% glucose, galactose, fructose, xylose, maltose, sucrose, lactose, starch (5 ml each) ,2 ml Fehling's A, 2 ml Fehling's B, 8 ml Benedict's reagent, 8 ml Barfoed's reagent, 3 g sodium acetate, 2 g phenylhydrazineHCl Materials: 12( 20 ml) test tubes, test tube rack, test tube brush, test tube holder, alcohol lamp, tripod, wire gauze, water bath, (10 ml) graduated cylinder, dropper, stirring rod, beaker(250 ml), spatula, microscope,7 glass slide, 7 cover slip, watch glass, platform balance Procedure: 1. Osazone formation -Mix 3 g sodium acetate and 2 g phenylhydrazineHCL and 14 ml distilled water. Warm with stirring until solution clears. Place 1 ml sugar solution (glucose, fructose, galactose, maltose, xylose, sucrose, lactose) in separate tube. Add 2 ml of the hot solution in each of the sugar solution, stopper with cotton, mix well and heat in a boiling water bath for 30 minutes. Cool at room temperature and examine the crystals under the microscope. Draw and compare the crystals. 2. Fehling's test – mix 2 ml Fehling's A with 2 ml Fehling's B and add 4 ml of water. Boil the solution for 1 minute. If the solution remains clear blue, place 1 ml of the solution in 8 separate test tubes. Add 5 drops of the sugar solution (glucose, fructose, galactose, xylose, maltose, lactose, sucrose, starch)in separate test tubes. Place the tubes in a boiling water bath for another 2 minutes and note the formation and color of precipitate. 3. Benedict's test – place 1 ml of Benedict's reagent in 8 separate test tubes. Add 5 drops of the sugar solution (use all 8 samples) in separate tubes. Place in a boiling water bath for 2 minutes. Cool and observe formation and color of precipitate. 4. Barfoed's test – place 1 ml Barfoed's reagent in 8 separate tubes. Add 5 drops of the sugar solution (use all 8 samples) in separate tubes. Place in a boiling water bath for 5 minutes. Cool and observe formation and color of precipitate.
Expert Solution
steps

Step by step

Solved in 2 steps

Blurred answer
Knowledge Booster
Lipids
Learn more about
Need a deep-dive on the concept behind this application? Look no further. Learn more about this topic, chemistry and related others by exploring similar questions and additional content below.
Recommended textbooks for you
Introductory Chemistry For Today
Introductory Chemistry For Today
Chemistry
ISBN:
9781285644561
Author:
Seager
Publisher:
Cengage
Chemistry for Today: General, Organic, and Bioche…
Chemistry for Today: General, Organic, and Bioche…
Chemistry
ISBN:
9781305960060
Author:
Spencer L. Seager, Michael R. Slabaugh, Maren S. Hansen
Publisher:
Cengage Learning
Organic Chemistry: A Guided Inquiry
Organic Chemistry: A Guided Inquiry
Chemistry
ISBN:
9780618974122
Author:
Andrei Straumanis
Publisher:
Cengage Learning