Chemical Equilibrium (Laboratory)?

Question

Why did the color of the Na2CrO4 solution change when 6M NH4OH was added?


thank you.

Answer 1

Are you sure you just added Ammonium hydroxide? The Sodium and Ammonium cations are colorless and the Chromate anion is yellow. The solution should have remained yellow.

Unless there was a trace amount of Iron or other contaminate, in which case the solution would turn green from the Chromium (III) ions.