Why does a solution containing the following equilibrium system turns yellow when NaOH is added:?

Question

Cr2O7(valence of -2)(aq)+H2O(l)<->2CrO4(valence of -2)(aq)+2H
Cr2O7 is orange and CrO4 is yellow

DOESNT SODUIM REACT AS WELL??

Answer 1

NaOH is a base. when you add it to the reaction, it forms water by combining with the H+ ions. the decrease in moles of H+ and consequential increase in moles of H2O causes the equilibrium to shift favoring the right.

this means that you form more CrO4 than Cr2O7 and the reaction appears more yellow than orange

Answer 2

2OH- + Cr2O7= ===> 2CrO4= + H2O

Cr2O7= is orange. CrO4= is yellow.

Sodium goes along for the ride.