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Inorganic Chemistry

Why dichromate changes into chromate in basic medium?

Profile image of Mayank Dak
7 Years agoGrade
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2 Answers

Profile image of Arun
7 Years ago
The equilibrium will shift to left in excess of H+ ions. Hence the more acidic the solution, the more the equilibrium is shifted to the left towards the dichromate ion and the colour of the solution  is orange.
When we add OH-  ion in solution (increasing the pH), it will react with H+ ion present in solution increasing the concentration of H2O.  
As the concentration of H2O will increase, the equilibrium will shift towards right and the concentration of chromate ions will increase and the colour of the solution will change to yellow.
 
Profile image of prince sunjot dutt
7 Years ago
Cr​​​2​O7_2-  +OH-   -----> Cr2O42- +H2O
This conversion can be explained by the fact that chromate and dichromate ion exits at equilibrium at a pH of 4.
Cr207_2- +H2O Cr2O4_2- + H+