Chromate ions react according to the following equation, where the left side of the reaction is yellow and the right side is orange.

Question

Chromate ions react according to the following equation, where the left side of the reaction is yellow and the right side is orange.

CrO42– + 2H+ ⇄ Cr2O72– + H2O

A student adds sodium hydroxide (NaOH) to the solution at equilibrium. In one to two sentences, describe and explain any changes to the solution that the student will observe.

Answer 1

The student will observe the solution turning back to yellow as the addition of NaOH will shift the equilibrium towards the left side of the reaction, favoring the formation of CrO42– ions which are yellow in color. This is because the hydroxide ions will react with the hydrogen ions, reducing their concentration and causing a shift in the equilibrium to counteract the change.