The reaction between an aldehyde and acidified potassium permanganate can be represented by the following equation:

$$5RCHO + 2KMnO_4 + 3H_2SO_4 \longrightarrow 5RCOOH + 2MnSO_4 + K_2SO_4 + 8H_2O$$

In this reaction, the aldehyde (RCHO) is oxidized to the corresponding carboxylic acid (RCOOH) by the permanganate ion (MnO4-). The permanganate ion is reduced to the manganese(II) ion (Mn2+). The reaction is typically carried out in an acidic solution, such as sulfuric acid (H2SO4), to protonate the aldehyde and facilitate the reaction.