To show the reaction between ethanol and Fehling’s reagent

Procedure

➢ The ethanal is placed in a test tube in a warm water bath

➢ Using a dropper, Fehling’s reagent is added to the ethanal

Result: The blue colour of Fehling’s reagent turns into a brick red precipitate

Note: When repeated with propanone in place of ethanal, no colour change is observed

What is Fehling’s reagent and why does it have a blue colour?

• Fehling’s reagent is an equal mixture of Fehling’s A and Fehling’s B

• The blue colour is caused by the presence of copper (II) (Cu+2) ions in the solution

Write the half reactions that occur when Fehling’s solution is added to ethanal

Explain the colour change that occurs when Fehling’s reagent is reacted with ethanal

• Fehling’s solution contains Cu 2+ ions causing a blue colour

• When reacted with ethanal Cu 2+ are reduced (gain 1 e –) to Cu+ ions

• Cu+ ions have a red colour and are not soluble so a brick red precipitate forms