Na2Cr2O7 + 2 KCl ® K2Cr2O7 + 2 NaCl
Orange crystals of potassium dichromate crystallise out The
chromates and dichromates are interconvertible in aqueous solution
depending upon pH of the solution The oxidation state of chromium
in chromate and dichromate is the same 2 CrO4
2– + 2H
+ ® Cr2O7
2– + H2O
Cr2O7
2– + 2 OH
- ® 2 CrO4
2– + H2O
The 
structures 
of
chromate ion, CrO4
2– and
the dichromate ion, Cr2O7
2–
are shown below