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amal amal
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13 years ago

Hi we conducted Benedicts, lugols,barfoeds,bials and seliwanoff test on 3 unknowns ( the possible unknowns are apple juice, honey and gatarode) and after performing tests we have to tell which unknown is which please see the picture attached  and reply me back
with which unknown is which     for example the answer could be like unknown 1 is honey etc.
 
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Staff Member
Educator
13 years ago
You have to find out what sugars are in which substance (i.e. what's in apple juice, honey, gatarode).

In lugols:

Tube   Solution   Initial colour   Final colour
1   Starch   Clear   Dark purple
2   Sucrose    Clear   Orange/bronze
3   Glucose   Clear   Orange/yellow
4   Water   Clear   Light orange

In Barfoed's:

It is used for detecting the presence of monosaccharides. It is based on the reduction of copper(II) acetate to copper(I) oxide (Cu2O), which forms a brick-red precipitate. [glow=red,2,300](Disaccharides may also react, but the reaction is much slower.)[/glow]

Seliwanoff’s test:

Fructose and sucrose are two common sugars which give a positive test. Sucrose gives a positive test as it is a disaccharide consisting of fructose and glucose.

Bial's Test:

The solution will turn bluish and a precipitate may form. Tests for pentoses...

Apple juice contains: fructose, glucose and sucrose

Will be Seliwanoff positive, Barfoed positive, and Orange yellow for lugols... So I am guessing number 1 is apple...

Honey contains: dextrose, levulose and maltose, Fructose and Glucose, sucrose
Gatorade: Aldoses and glucose
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amal Author
wrote...
13 years ago
 Yes i have figured out unknown 1 is apple

but still confused about unknown 2 and 3? which one is honey and gatarode
wrote...
Staff Member
Educator
13 years ago
2 = honey
3 = gatorade
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