An aldehyde produces a brick red precipitate; a ketone does not react.
Benedict's solution contains copper(II) ions in a sodium carbonate solution.
The copper(II) ions are complexed with citrate ions to prevent the formation of a precipitate of copper(II) carbonate.
A few drops of the aldehyde or ketone are added to the Benedict solution, and the mixture is warmed gently for a few minutes.
With a ketone, there will be no change in the blue solution.
In a positive test for an aldehyde, the blue solution produces a dark red precipitate of copper(I) oxide.
An aldehyde reduces the complexed
The equations for the reaction are