. Chromate ion is yellow, under acidic conditions it is in equilibrium with the

Question

. Chromate ion is yellow, under acidic conditions it is in equilibrium with the dichromate ion which is orange.

                                                2 CrO42-    +   2 H+(aq)   ?   Cr2O72-(aq)   +   H2O       DH < 0 kJ

                                                yellow                                  orange             

State how the following will affect an equilibrium mixture of chromate and dichromate ion. State whether the equilibrium will shift right, left or be unchanged and what you will see with regard to the color of the solution.

A. add nitric acid

B. add sodium hydroxide

C. add K2Cr2O7

D. place in ice bath

Explanation / Answer

A) Addition of HNO3 shifts the eqb top right as it will increase the concentration of H+.

B) Addition of NaOH will shift the eqb. to left as NaOH will consume H+ & decrease its concentration

C) Addition of K2Cr2O7 shifts the eqb top left as it will increase the concentration of Cr2O72-.

D.) Since the reaction is exothermic , therefore decrease in temperature will shift the eqb. to the right

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