Propanal and propanone are both organic compounds containing the carbonyl group. Describe how you could use Tollens' reagent to distinguish between propanal and propanone, and explain the observations you would expect for each compound.

Add a small amount of propanal to a test tube and then add a few drops of Tollens' reagent, followed by gentle warming. The aldehyde group is oxidised to a carboxylic acid, and the silver ions are reduced to metallic silver, giving a bright silver mirror on the inner wall of the tube.

Add a small amount of propanone to a separate test tube and repeat the same procedure. The ketone is not oxidised, so the silver ions remain in solution and no silver precipitate forms; the tube stays colourless.

Thus, a silver mirror indicates the presence of an aldehyde (propanal), while the absence of a mirror indicates a ketone (propanone).