“Vasile Alecsandri” High School, Galati, Romania
The necessary Fehling reactive is prepared using:
1) Fehling 1 solution-we dissolve 7g of copper sulphate in 100ml water
2) Fehling 2-we dissolve 35g Seighette salt and 26g potassium hydrate in 100ml water
In the experiment we use equal parts of both solutions.
We introduce in a clean test tube 2-3 ml Fehling reactive and we boil it; meanwhile we drip in the test tube washy glucose solution 20-25% until the blue color of the blend disappears and a red copper oxide precipitate appears.
CuSO4 + 2 KOH = Cu(OH)2 + K2SO4
C6H12O6 + 2 Cu(OH)2 = C6H12O7 + Cu2O + 2 H2O
Glucose --> Gluconic acid
C6H12O6 + 2 Cu(OH)2 = C6H12O7 + Cu2O + 2 H2O
Glucose --> Gluconic acid
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