What is the effect of increasing pH on a solution of potassium dichromate????

plz help me in dis!!

The dichromate ion(Cr2O72-) exists in equilibrium with chromate(CrO42-) ion at pH 4, However by changing the pH, they can be inter converted.

Effect of decrease in pH

chromate (yellow)-------->dichromate(orange)

2CrO42- + 2H+ → Cr2O72-+ H2O

Effect of increase in pH

dichromate(orange)--------------->chromate (yellow)

Cr2O72-+ 2OH- → 2CrO42- + H2O


The structures of chromate ion, CrO42- and the dichromate ion,Cr2O72- are shown below...

The chromate ion is tetrahedral whereas the dichromate ion consists of two tetrahedral sharing one corner with Cr–O–Cr bond angle of 126°.

Hope this answers your query.!

Good luck!

  • 31

in the solution , dichromate ions(cr2o7)2- exists in equillibrium with chromate ions (cro4)2- as follows:

                           (cr2o7)2-+H2O -------->2(cro4)2-+2H+

In the alkanline medium..,

the equillibrium shifts in the forward direction

and the solution is yellow. 



  • -9

thnx :)

  • 1
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