Name Carbohydrates Date Partner Section UKNOWN CODE, NOR I pt for each blank /60
ID: 228793 • Letter: N
Question
Name Carbohydrates Date Partner Section UKNOWN CODE, NOR I pt for each blank /60 TEST A Molisch Test-Test for carbohydrate Conclusion Compounds Tested Observation Ribose Fructose Glucose Maltose Sucrose Posihive Positve Unknown TEST B - Seliwanoff's Test - Test for ketoses Compounds Tested Observation Conclusion Ribose Fructose Glucose Maltose orange red ne clear Clear Sucrose ord r e dt Unknown Clear TEST C-Bial's test- Test for pentoses Compound:s Tested Observation Conclusion Ribose Penor Fructose brown Glucose ycliawIGreen Maltose Sucrose hexose pendose Unknown blue
Explanation / Answer
For Benedict's test if the final color is brick red/copper then we can say that it is reducing sugar, if not a reducing
sugar then the solution will have blue/colorless solution.
1. Ribose is the unknown compound
2. First thing one should verify is that whether the unknown is monosaccharide or not. Since it showed up
positive in this Barfoed's test we can say that it is monosaccharide and all monosaccharides are reducing
sugars, which is why it gave a copper solution in Benedict's test. All reducing sugars have aldehyde group.
Fructose and sucrose are hexoses clearly hence omitted out of the 5 choices. Maltose is not reducing sugar
Hence it all comes down to glucose and ribose, in Test A the unknown compound shows same result as
Ribose. Hence the unknown is "Ribose".
3. If we perform same tests we can get the following results through which the unknowns can be labelled
Sorbose shows positive results for Tests A, B, D, E. Hence it is a ketose
Lactose shows postive results for Tests A,C, D. Hence it is disacchride with aldose form
Xylulose shows positive results for Tests A, B, C, D, E, It is a monosacchride with keto-pentose form
Sucrose shows positive results for Tests A,B, E. It is disacchride with hexose form
Nylon is carbohydrate but a polysacchride hence only Test A will show positive result.
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