The chemical test called a brown ring test is conducted to find out the presence of Nitrate ions in any solution, in which the solutions form a brown ring in the test tube.
The above test is also called the brown ring test, in which the brown ring complex compound is formulated as[Fe(H2O)5NO]SO4.
Here the oxidation state of Iron in the complex, can be found as:
We can assume that the oxidation state of Iron metal is x.
Here the oxidation state of the Sulphate ion is−2, the oxidation state of water is zero and the oxidation state of Nitroso NO is +1.Hence, the oxidation state of Iron can be calculated as:
⇒x+(+1)+5(0)=+2⇒x=+1