Describe the principle involved in the manufacture of ammonia by Haber's process. Whathappens when ammonia gas is passed through heated CuO?

Despite H₂SO₄ being a very good moisture absorbing compound, it cannot be used to dehydrate ammonia gas because ammonia gas reacts with Sulphuric Acid when passed over it.

The reaction is as follows:

2NH₃ + H₂SO₄ ----> (NH₄)₂SO₄

(Ammonium Sulphate)

In the ring test of nitrate ion, Nitrosylferrous Sulphate (FeSO₄.NO) - an unstable complex salt is formed. Due to the formation of this compound, a brown coloured ring is seen in the undisturbed test tube.

When FeSO4 is added to the mixture of HNO3 and conc. H2SO4, it give brown ring of  Nitrosylferrous Sulphate (FeSO4.NO) which forms on the point of contact of the two reagents. 

It is used to give the test of nitric acid known as brown ring test. 

When the White ppt. obtained by treating NaCl solution with Ag NO3 solution is again treated with ammonia solution, it forms a water soluble salt, that will make the solution clear. 

NaCl (aqueous)  Na⁺  + Cl ^- 

Conc. H2SO4 and anhydrous CaCl₂ are not used to dry ammonia because they form chemical compounds with it. 

- conc. H2SO4  and NH3 form (NH) SO  

- While anhydrous  CaCl₂ absorbs water, it undergoes hydrolysis to give hydrochloric acid.

Since ammonia is basic, it is neutralised by HCl to give salt,  NH3 + HCl NH4Cl.

Ammonia passed through the paper turns mercurous nitrate paper into black. It is due to the formation of...

Ammonia cannot be dried by passing over conc. H2SO4  because ammonia gas reacts chemically with conc. H2SO4 to form (NH) SO  ammonium sulphate. 

Conc. H2SO4 is a very good oxidizing agent. 

Aqua regia is a mixture of nitric acid (HNO₃) and hydrochloric acid (HCl), in a molar ratio of 1:3. 

Aqua regia is capable of dissolving gold.