In the method of testing nitrate, if it is nitrate, you need to add concentrated sulfuric acid and copper, how to write the equation

In the method of testing nitrate, if it is nitrate, you need to add concentrated sulfuric acid and copper, how to write the equation

Cu+4HNO3(concentrated)=Cu (NO3)2+2H2O+2NO2

To test nitrate, select copper and concentrated sulfuric acid as reagents, heat equation and phenomenon For the test of nitrate, the selected reagent is copper and concentrated sulfuric acid, and the equation and phenomenon of heating

Nitrate ion test
Objective: To understand the method of detecting nitrate ion.
Articles: test tube, test tube rack, test tube clamp, measuring cylinder.
Potassium nitrate, ferrous sulfate, concentrated sulfuric acid.
Rationale: Nitrate ions are oxidizable, allowing ferrous ions to oxidize to iron ions in acidic solutions and reducing themselves to nitric oxide. Nitric oxide combines with many metal salts to form unstable nitroso compounds.
3Fe2++NO3-+4H+=3Fe3++2H2O+NO
FeSO4+NO=Fe (NO) SO4
This reaction is often used in the laboratory to test nitrate ions, known as brown-ring tests. This simple nitroso compound exists only in the solution, where nitric oxide escapes completely when heated.
Nitrite ions can react similarly. To distinguish these two kinds of acid ions can use concentrated phosphoric acid. Nitrite ions can appear dark brown while nitrate ions can not.
Preparation and operation: pour 3 ml of potassium nitrate solution and 3 ml of ferrous sulfate solution into the test tube, shake the test tube and mix evenly. Hold the test tube, slowly inject 3 ml of concentrated sulfuric acid along the test tube wall (Fig.7-97), make the concentrated sulfuric acid with higher density sink into the bottom of the test tube, and divide it into two layers with the mixed solution of potassium nitrate and ferrous sulfate. Wait a moment, slowly vertical the test tube, and soon, a brown ring is formed between the two layers of liquid.
Precautions: ferrous sulfate must be newly prepared and sulfuric acid must be concentrated. Do not muddy the solution during operation.
Other experimental methods: It is suitable for solid nitrate or rather concentrated nitrate solution. Put a small amount of nitrate crystal or concentrated solution into the test tube, then add a small amount of concentrated sulfuric acid (1∶1). Then add a small piece of copper sheet into the test tube. When the test tube is heated, red-brown gas is produced, which proves that it contains nitrate ion.
Cu+2NO3-+4H+Cu2++2NO2↑+2H2O