Please answer the following questions using the information provided: Experiment

Question

Please answer the following questions using the information provided:

Experiment 12 Postlaboratory Assignment Carbohydrates Name: Lab Instructor: Date Record each answer in the space provided l. Name or describe a test that can differentiate e following pairs. A. Fructose (hexose and Arabinose (pentose) B. Maltose (mono) and Mannose (di) C. Sucrose and Starch D. Fructose (ketose) and Galactose (aldose) 2. A molecule (one of the known standards from this experiment) re acts with Barfoed's solution, gives a brown color with Bial's reagent, and a red color with Seliwanoff's solution. Identify the compound. 167

Explanation / Answer

1)

a) fructose (hexose) and arabinose (pentose):

by using Bial's test, we can differentiate the fructose and arabinose

procedure: Two mL of sample solution is placed in test tube. Two ml of Bial's reagent ( a solution of orcinol,HCl and ferric chloride) is added. the solution then heated gently in abunsen burner or hot water bath. if the color is not obvious, more water can be added to the tube.

b) maltose(mono) and mannose (di):

benedict's reagent is used to differentiate the maltose and mannose

procedure : it is a solution of deep blue alkaline solution used to test the presence of -CHO aldehyde fuynctional group. take substance add 3 mL of Benedict's solution then boil for few minutes and allow to cool .

c) sucrose and starch:

Iodine test is used to differentiate the sucrose and starch.

procedure: a small amount of sample add few ml of water and few drops of KI solution .

d) fructose(altose) and galactose(aldose):

Seliwanoff's test specific for ketose. this test is clearly differentiate the galactose and fructose

procedure: when conc.HCl solution added , ketoes undergo dehydration to yield red color.

2)

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