The acidic aqueous solution of ferrous ion forms a brown complex in the presence of `NO_(3)^(Θ)` by the follwing two steps:
`[Fe(H_(2)O)_(6)]^(2+) +NO_(3)^(Θ) + H^(o+) rarr … + [Fe(H_(2)O)_(6)]^(3+) + H_(2)O`
`[Fe(H_(2)O)_(6)]^(2+) +…rarr… + H_(2)O`
Complete and balance the equations .

Explanation

`3[Fe(H_(2)O)_(6)]^(2+) +NO_(3) Θ + 4H^(o+)`
`rarrNO + 3[Fe(H_(2)O)_(6)]^(3+) +2H_(2)O`
`[Fe(H_(2)O)_(6)]^(2+) + NO rarr [Fe(H_(2)O)_(5)NO]^(2+) + H_(2)O` .