CGPET 2017 Solved Paper

The oxidation state of Fe in Brown ring is +1. The complex formed is [Fe(H2O)5NO]SO4. The charge on anion is −2. Hence, charge on cation complex has to be +2 as ring is electrically neutral. The charge on Fe on calculation comes as +2. But as the electrontransfer takes place from NO to Fe.
Hence, NO and Fe acquire a charge of +1 each.