$2 CrO _{4}^{2-} \frac{\text { In acidic medium }}{ H ^{+}} \rightarrow Cr _{7} O _{7}^{2-}+ H _{2} O$
Potassium dichromate is orange in color and used in redox titrations. But it is not stable in both acid and base.
$Cr _2 O _7^{2-}+ XH ^{+}+6 Fe ^{2+} \rightarrow YCr ^{3+}+6 Fe ^{3+}+ ZH _2 O$
$X , Y$ અને $Z$ નો સરવાળો $......$ છે.