Fehlings test

Question 1

Fehling’s solution is an

Answer 1

alkaline solution containing copper(II) ions which act as the oxidising agent

Question 2

Fehling’s solution When warmed with an aldehyde, the aldehyde is oxidised to a

Answer 2

carboxylic acid and the Cu2+ ions are reduced to Cu+ ions

Question 3

In the alkaline conditions, the

Answer 3

the carboxylic acid formed will be neutralised to a carboxylate ion (the -COOH will lose a proton to become -COO- )

The carboxylate ion (-COO-) will form a salt with a positively charged metal ion such as sodium (-COO-Na+)

Question 4

The clear blue colour of the solution turns

Answer 4

opaque red due to the formation of a copper(I) oxide precipitate

Question 5

Ketones cannot be oxidised and therefore give a ………….test when warmed with Fehling’s solution

Answer 5

Negative