![Page 1: The Fehlings Test or Benedicts for use in a Chemistry or a Biology Class. Section 7.4 of chemistry syllabus and 1.3.4 of biology syllabus](https://reader035.vdocument.in/reader035/viewer/2022062600/5a4d1b6e7f8b9ab0599b462e/html5/thumbnails/1.jpg)
The Fehling’s Test or Benedict’s for use in a Chemistry or a
Biology Class.Section 7.4 of chemistry syllabus
and 1.3.4 of biology syllabus.
![Page 2: The Fehlings Test or Benedicts for use in a Chemistry or a Biology Class. Section 7.4 of chemistry syllabus and 1.3.4 of biology syllabus](https://reader035.vdocument.in/reader035/viewer/2022062600/5a4d1b6e7f8b9ab0599b462e/html5/thumbnails/2.jpg)
• Reducing sugars e.g. glucose, fructose, galactose and maltose reduce Benedict’s or Fehling’s solution.
• Aldehydes also reduce Fehling’s solution.
• Reducing sugars contain the – CHO functional group.
• So do aldehydes.• It is the – CHO group which makes
them good reducing agents.
![Page 3: The Fehlings Test or Benedicts for use in a Chemistry or a Biology Class. Section 7.4 of chemistry syllabus and 1.3.4 of biology syllabus](https://reader035.vdocument.in/reader035/viewer/2022062600/5a4d1b6e7f8b9ab0599b462e/html5/thumbnails/3.jpg)
• To do the Benedict’s test follow the method in the next 9 slides.
• A colour change from blue to red occurs if a reducing sugar or aldehyde is present in the test solution.
![Page 4: The Fehlings Test or Benedicts for use in a Chemistry or a Biology Class. Section 7.4 of chemistry syllabus and 1.3.4 of biology syllabus](https://reader035.vdocument.in/reader035/viewer/2022062600/5a4d1b6e7f8b9ab0599b462e/html5/thumbnails/4.jpg)
To conduct a qualitative test for reducing sugar or an
aldehyde
![Page 5: The Fehlings Test or Benedicts for use in a Chemistry or a Biology Class. Section 7.4 of chemistry syllabus and 1.3.4 of biology syllabus](https://reader035.vdocument.in/reader035/viewer/2022062600/5a4d1b6e7f8b9ab0599b462e/html5/thumbnails/5.jpg)
Before you start get or make a copy of this
Table of results
Sample Initial colour Final colour
A – Glucose solution
B – Water
![Page 6: The Fehlings Test or Benedicts for use in a Chemistry or a Biology Class. Section 7.4 of chemistry syllabus and 1.3.4 of biology syllabus](https://reader035.vdocument.in/reader035/viewer/2022062600/5a4d1b6e7f8b9ab0599b462e/html5/thumbnails/6.jpg)
Step 1
Label two boiling tubes A and B.
![Page 7: The Fehlings Test or Benedicts for use in a Chemistry or a Biology Class. Section 7.4 of chemistry syllabus and 1.3.4 of biology syllabus](https://reader035.vdocument.in/reader035/viewer/2022062600/5a4d1b6e7f8b9ab0599b462e/html5/thumbnails/7.jpg)
Step 2
Place 2 ml of glucose solution into tube A.
![Page 8: The Fehlings Test or Benedicts for use in a Chemistry or a Biology Class. Section 7.4 of chemistry syllabus and 1.3.4 of biology syllabus](https://reader035.vdocument.in/reader035/viewer/2022062600/5a4d1b6e7f8b9ab0599b462e/html5/thumbnails/8.jpg)
Step 3
Place 2 ml water into tube B.
![Page 9: The Fehlings Test or Benedicts for use in a Chemistry or a Biology Class. Section 7.4 of chemistry syllabus and 1.3.4 of biology syllabus](https://reader035.vdocument.in/reader035/viewer/2022062600/5a4d1b6e7f8b9ab0599b462e/html5/thumbnails/9.jpg)
Step 4
Add 2 ml of Fehling’s solution into each tube and swirl.
![Page 10: The Fehlings Test or Benedicts for use in a Chemistry or a Biology Class. Section 7.4 of chemistry syllabus and 1.3.4 of biology syllabus](https://reader035.vdocument.in/reader035/viewer/2022062600/5a4d1b6e7f8b9ab0599b462e/html5/thumbnails/10.jpg)
Step 5
Place both tubes in a water bath and heat for 5 minutes.
![Page 11: The Fehlings Test or Benedicts for use in a Chemistry or a Biology Class. Section 7.4 of chemistry syllabus and 1.3.4 of biology syllabus](https://reader035.vdocument.in/reader035/viewer/2022062600/5a4d1b6e7f8b9ab0599b462e/html5/thumbnails/11.jpg)
Expected Result
Positive: brick red
Negative: blue
![Page 12: The Fehlings Test or Benedicts for use in a Chemistry or a Biology Class. Section 7.4 of chemistry syllabus and 1.3.4 of biology syllabus](https://reader035.vdocument.in/reader035/viewer/2022062600/5a4d1b6e7f8b9ab0599b462e/html5/thumbnails/12.jpg)
Step 6
Table of results
Sample Initial colour Final colour
A – Glucose solution
B – Water
![Page 13: The Fehlings Test or Benedicts for use in a Chemistry or a Biology Class. Section 7.4 of chemistry syllabus and 1.3.4 of biology syllabus](https://reader035.vdocument.in/reader035/viewer/2022062600/5a4d1b6e7f8b9ab0599b462e/html5/thumbnails/13.jpg)
Some Revision Questions.• Name a reducing sugar.• Glucose.• Name an aldehyde with two carbon atoms
per molecule.• Ethanal.• What reagent is reduced by both
aldehydes and monosaccharides.• Fehling’s solution.
![Page 14: The Fehlings Test or Benedicts for use in a Chemistry or a Biology Class. Section 7.4 of chemistry syllabus and 1.3.4 of biology syllabus](https://reader035.vdocument.in/reader035/viewer/2022062600/5a4d1b6e7f8b9ab0599b462e/html5/thumbnails/14.jpg)
Some Revision Questions.• When doing the Fehling’s test, is heat
required?• Yes.• What is the colour change if the test
solution reduces Fehling’s solution?• Blue to Red.
![Page 15: The Fehlings Test or Benedicts for use in a Chemistry or a Biology Class. Section 7.4 of chemistry syllabus and 1.3.4 of biology syllabus](https://reader035.vdocument.in/reader035/viewer/2022062600/5a4d1b6e7f8b9ab0599b462e/html5/thumbnails/15.jpg)
Some more Questions.• Sucrose, maltose and lactose are three
disaccharides. Which is the odd one out?• Maltose because it reduces Fehling’s
solution or Benedict’s reagent.• A compound with three carbon atoms per
molecule contains a carbonyl group. It does not reduce Fehling’s solution. Identify this compound.
• Propanone or acetone.