According to Le Chatelier's Principle, when changes occur, there will be a counter-act that counters the change to the system.

According to Le Chatelier’s Principle, when changes occur, there will be a counter-act that counters the change to the system.In Part IV, steps 1 to 4, when H+ ions are added to the system, the reaction will shift from high to low.K2CrO42- with addition H+ will shift the equilibrium as the colour change from yellow to orange. For K2Cr2O72- with addition OH- the equilibrium will shift, and the colour will change from orange to yellow.