Dichromate ion in acidic medium oxidizes stannous ion as
x––Sn2++y–Cr2O2−7+z–H+→a––Sn4++b–Cr3++c–H2O then
The value of x : y is 1 : 3
The value of x + y + z is 18
a : b is 3 : 2
the value of z- c is 7
3Sn2++1Cr2O2−7+14H+→3Sn4++2Cr3++7H2O
xSn2++yCr2O2−7+zH+→aSn4++bCr3++cH2O