What happens when the pH of a solution of potassium dichromate ($ ext{K}_2 ext{Cr}_2 ext{O}_7$) i

Question

What happens when the pH of a solution of potassium dichromate ($	ext{K}_2	ext{Cr}_2	ext{O}_7$) is gradually increased by adding an alkali?

Professor PC Thomas Classes · Answer

The dichromate ion ($	ext{Cr}_2	ext{O}_7^{2-}$, orange) and chromate ion ($	ext{CrO}_4^{2-}$, yellow) exist in a pH-dependent equilibrium. Increasing the pH (adding alkali) shifts the equilibrium towards the formation of the yellow chromate ion.