Question

For which radical brown ring test is performed?

Answer 1

Brown Ring Test Procedure:

• A common nitrate test is also known as the brown ring test. The experiment can be performed as follows:

Step 1: Take the solution of nitrate.

Step 2: Add iron(II) sulfate

Step 3: Slowly add concentrated sulphuric acid (H₂SO₄) such that the acid added forms a layer below the aqueous solution.

Result – A ring brown in color will be formed at the junction of the 2 layers. This indicates the presence of nitrate ion.

Brown Ring Test Reaction:

The overall reaction is given below:

Reduction of the nitrate ion, oxidation of iron(II) and reduction of nitric oxide.

$$\begin{gathered} \underset{Ferroussulphate}{6FeS{O}_4\left(s\right)}+\underset{Sulfuricacid}{3H_{2}S{O}_4\left(l\right)}+\underset{Nitricacid}{2HN{O}_3\left(l\right)}\to \underset{Ferricsulfate}{3F{e}_2{\left(S{O}_4\right)}_3}\left(s\right)+4H_{2}O+\underset{Nitricoxide}{2NO\left(g\right)} \\ FeS{O}_4\left(s\right)+NO\left(g\right)\to \underset{Nitrosoferroussulfate(brownprecipitate)}{FeS{O}_4.NO\left(s\right)} \end{gathered}$$

• Nitrates and Nitric acid($\mathit{H}\mathit{N}{\mathit{O}}_{\mathbf{3}}$) give brown ring test with Ferrous sulfate($\mathit{F}\mathit{e}\mathit{S}{\mathit{O}}_{\mathbf{4}}$) and concentrated Sulfuric acid (${\mathit{H}}_{\mathbf{2}}\mathit{S}{\mathit{O}}_{\mathbf{4}}$) solution.

• Here, nitric oxide is radical.
• So, the radical which gives the Brown ring test is Nitric oxide.