Why does potassium dichromate always reacts in an acidic medium? On the other hand, potassium manganate reacts in both acidic and alkaline media.
In an alkaline medium, chromium(VI) exists as potassium chromate instead of potassium dichromate:

$$\ce{Cr2O7^2- + 2OH- &lt;=&gt;&gt; 2CrO4^2- + H2O}$$

Wikipedia has more information about this equilibrium.