Hey!

this is a redox reaction, where dichromate is the oxidizing agent .

and here we would use half equation method:

So, reduction half equation is :

Cr2O72- + 14 H+ + 6e- => 2Cr3+ + 7H2O (l)

and the oxidation half equation is :

Fe2+ => Fe 3+ + e-

and then add these both equations in such a way that all the electrons are eliminated:

6Fe2+ + Cr2O72- + 14H+ => 6Fe3+ + 2Cr3+ + 7H2O (l)

hope it helps, thanks!