EXERCISE 5 GENERAL TEST AND COLOR TEST FOR CARBOHYDRATES

Question 1

• is a quantitative or qualitative procedure intended to prove the existence or measure of a chemical compound and or a chemical group with the help of a reactant.

Answer 1

Chemical Test

Question 2

What are the six sugar samples?

Answer 2

frutose
glucose
galactose
sucrose
maltose
lactose

Question 3

• it is used to measure, hold, mix, or heat small quantities of solid or liquid chemical samples.

Answer 3

Test tube

Question 4

• it is used to hold multiple test tubes upright at the same time

Answer 4

Test tube rack

Question 5

• it is used to heat and combust substances, and to sterilize objects on high heat.

Answer 5

Bunsen burner/Alcohol lamp

Question 6

• it is used to measure the volume of liquid samples

Answer 6

Graduated cylinder

Question 7

• it is used for the evaporation of solutions and supernatant liquids

Answer 7

Evaporating dish

Question 8

• it is used to collect and transfer small quantities of liquids

Answer 8

Medicine dropper

Question 9

what is the positive color for Molisch test?

Answer 9

(purple/purple ring)

Question 10

what is the positive color for Anthrone’s reagent

Answer 10

(bluish green)

Question 11

what is the positive color for Benedict’s test

Answer 11

(red)

Question 12

what is the positive color for Barfoed’s test

Answer 12

(red)

Question 13

what is the positive color for Nylander’s test

Answer 13

(black)

Question 14

what is the positive color for Tollen’s test

Answer 14

(dark gray/silver)

Question 15

what is the positive color for Picric acid test

Answer 15

(red)

Question 16

• In this test, concentrated sulfuric acid converts the given carbohydrate into furfural or its derivatives, which react with α-naphthol to form a purple coloured product. (Presence of Carbohydrates)

Answer 16

Molisch test

Question 17

• Anthrone’s reagent first hydrolyse carbohydrates into component monosaccharide. The concentrated acid then catalyzes the dehydration of the monosaccharides to form furfural or hydroxyl furfural. Furfural or hydroxyl furfural condenses with two molecules of α-naphthol from the Anthrone’s reagent to form a blue-green complex. (Detection and Quantification of Carbohydrates)

Answer 17

Anthrone’s test

Question 18

• In the presence of an alkali and heat, reducing sugars are transformed into enediols (which is a relatively powerful reducing agent). Benedict’s reagent’s cupric ions (Cu2+) are converted to cuprous ions (Cu+) when reducing sugars are present in the analyte. These cuprous ions combine with the reaction mixture to produce copper(I) oxide, which precipitates as a brick-red substance. (Sample contains Reducing sugars)

Answer 18

Benedict’s test

Question 19

• The reduction of cupric acetate by reducing monosaccharides and reducing disaccharides forms the basis of Barfoed’s test reaction. Brick red precipitate is produced when cupric acetate is reduced to cuprous oxide. Typically, monosaccharides react in 1 to 5 minutes and form a crimson precipitate. (Presence of monosaccharides)

Answer 19

Barfoed’s test

Question 20

• Black precipitates are formed when free ketone or aldehyde groups of carbohydrates reduce to generate bismuth subnitrate, which then reduces to black bismuth. This test can detect glucose levels as low as 0.08 percent. (Sample contains Reducing sugars)

Answer 20

Nylander’s test

Question 21

• Carbohydrates react with Tollens reagent and forms a silver mirror on the inner walls of the test tube. This confirms the presence of reducing sugars. Silver ions are reduced to metallic silver. (Sample contains Reducing sugars)

Answer 21

Tollen’s test

Question 22

• Picric acid reactions happen with the reducing sugars to make Picramic acid, which is red in color. Reduced characteristics are seen in all monosaccharides and disaccharides that have a potentially free aldehyde or ketone group that possesses reducing properties. Reducing sugars have a free aldehyde or ketone group which has the ability to reduce. (Sample contains Reducing sugars)

Answer 22

Picric acid test

Question 23

• This test includes a chemical analysis that separates aldose (monosaccharide, aldehyde group) from ketose (monosaccharide,ketone group). A sugar is a ketose if it has a ketone group in it. A sugar is an aldose if it has an aldehyde group. This experiment is based on the idea that when heated, ketoses dehydrate more quickly than aldoses. Furthermore, the formation of the cherry red-colored complex indicates a positive result which means that the given sample contains ketoses. (Sample contains Ketoses)

Answer 23

Seliwanoff’s test

Question 24

Aldose and Ketose Sugars

Answer 24

Fructose - Ketose sugars

Glucose - Aldose sugars

Galactose - Aldose sugars

Maltose - Aldose and Ketose sugars

Lactose - Aldose and Ketose sugars

Sucrose - Aldose and Ketose sugars

Question 25

What makes Anthrone’s test and Molisch’s test a general test for carbohydrates?

Answer 25

The Athrone’s test is another general term for carbohydrates. Anthrone is a tricyclic aromatic ketone, and it is used for the detection and quantification of carbohydrates in various samples like blood serum, milk, and its variation. Furthermore, monosaccharides result in a positive test result in Molisch’s test more quickly. While polysaccharides and disaccharides react slowly with the Molisch reagent, and it postpones the positive result, respectively. As a result,

Question 26

What is the difference between Benedict’s test and Barfoed’s test?

Answer 26

Benedict’s test would determine if the sample is a reducing sugar. On the contrary, the Barfoed’s test would determine if it is a monosaccharide or disaccharide. Since both tests are positive when a reddish precipitate occurs, they must be performed separately in order to determine which test is producing the positive result.