Question

Write the reaction involved in large scale preparation of nitric acid?

Answer 1

Nitric acid is a strong mineral acid. It is a mono-basic acid. It is a strong oxidizing agent and can oxidize metals and nonmetals easily. 
It is used in the manufacture of fertilizers, silk industry, explosive materials such as (T.N.T) etc.

INDUSTRIAL PREPARATION
OF NITRIC ACID

 

    OSTWALD' s METHOD

OSTWALD'S METHOD

 

    Materials used:
     Ammonia gas 
     Water 
     Oxygen gas

CATALYST

 

    Platinum

DETAILS OF PROCESS

 

    First step

PRIMARY OXIDATION
(formation of nitric acid)

 Oxidation of ammonia is carried out in a catalytic chamber in which one part of ammonia and eight parts by volume of oxygen are  
 reacted. The temperature of chamber is about 600oC. This chamber contains platinum gauze which serves as catalyst.
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CHEMISTRY OF
PRIMARY OXIDATION



 Oxidization of ammonia is a reversible and exothermic reaction. Therefore according to Le- chatelier's principle,a decrease in temperature
 favours the reaction in forward direction. In primary oxidization 95% of ammonia is converted into nitric oxide (NO).

    Second step

SECONDARY OXIDATION
(formation of nitrogen dioxide)

  Nitric oxide gas obtained by the oxidation of ammonia is very hot. In order to reduce its temperature, it is passed through a heat 
  exchanger where the temperature of nitric oxide is reduced to 150oC. Nitric oxide after cooling is transferred to another oxidizing tower
  where at about 50oC it is oxidizing to NO2.



    Third step

ABSORPTION OF NO2 
(formation of HNO3)

    Nitrogen dioxide from secondary oxidation chamber is introduced into a special absorption tower. 
    NO2 gas passed through the tower and water is showered over it. By the absorption, nitric acid is obtained.

3 NO2 + H2O 2HNO3 + NO

    Nitric acid so obtained is very dilute. It is recycled in an absorption tower so that more and more NO2get absorbed. HNO3 after
    recycle becomes about 68% concentrated.



    Fourth step

CONCENTRATION

    In order to increase the concentration of HNO3 , vapour of HNO3 are passed over concentrated H2SO4. Being a dehydrating agent 
   H2SO4, absorbs water from HNO3 and concentrated HNO3 is obtained.