Oxyacids of Nitrogen

Oxyacids of Nitrogen

Nitrous acid, Nitric acid, Hyponitrous acid


Oxyacids of Nitrogen:

  1. Nitrous acid - HNO2
  2. Nitric acid - HNO3
  3. Hyponitrous acid - H2N2O4
  1. Nitrous Acid: HNO2

    Preparation
    :
     
    1. By dissolving N2O3 in water

      N2O+ H2 2HNO2

      By action of acid on metallic nitrites

      NaNO2 + HCl  NaCl + HNO2
       
    2. By oxidation of NH3

      NH+ 3H2O HNO+ 4H2O

    Properties:
     

    1. It is a weak acid and does not exist in free state.
       
    2. 2HNO NO + NO+ H2O (Vapour phase)

      3HNO HNO3 + H2O + 2NO (Aqueous solution)
       
    3. Oxidising property

      2HNO2NO + H2O + [O]

      H2S + [O]  H2O + S

      SO2 + H2O + [O]  H2SO4

      2FeSO4 + H2SO4 + [O]  Fe2(SO4)3 + H2O

      SnCl2 + 2HCl + [O]  SnCl4 + H2O

      2Kl + H2O + [O]  2KOH + l2
       
    4. Reducing property

      HNO+ [O]  HNO3

      K2Cr2O+ 4H2SO4 + 3HNO K2SO+ Cr2(SO4)3 + 3HNO3 + 4H2O

      2KmnO4 + 3H2SO4 + 5HNO2  K2SO4 + 2MnSO+ 3H2O + 5HNO3

      Br2 + H2O + HNO2  HNO3 + 2HBr
       
    5. H2NCONH2 + 2HNO2  CO2 + 2N2 + 3H2O

       
  2. Nitric acid: HNO3

    Preparation
    :

    1.  By heating sodium nitrate with conc. sulphuric acid.

      2NaNO3 + H2SO4  2HNO3 + Na2SO4
       
    2. Birkeland - Eyde Process

      N2 + O2  2NO

      2NO + O2  2NO2

      3NO2 + H2 2HNO3 + NO
       
    3. Ostwald's Process -

      4NH3 + 5O 4NO + 6H2O

      2NO + O2  2NO2

      3NO2 + H2 2HNO+ NO

      Structure:  

    Properties:

    Anhydrous acid is a color less fuming liquid.
    It usually acquires yellow color due to its decomposition by sunlight into NO2.

    4HNO 4NO2 + 2H2O + O2

    C12H22O11 + 18[O]  6H2C2O+ 5H2O

    Reaction with Metals

     
    1. Mg + 2HNO3 (dil)  Mg(NO3)2 + H2
       
    2. 3Mg + 8HNO3 (conc.)  3Mg (NO3)2 + 4H2O + 2NO
       
    3. 3Cu + 8HNO3 (cold and dilute)  3Cu(NO3)2 + 4H2O + 2NO
       
    4. Cu + 4HNO(cold and conc.)  Cu(NO3)2 + 2H2O + 2NO2

      [Ag, Pb and  Bi also react as Cu]
       
    5. 6Hg + 6HNO3 (dilute)  3Hg2(NO3)2 + 4H2O + 2NO
       
    6. Hg + 4HNO3 (conc.)  Hg(NO3)+ 2H2O + 2NO2
       
    7. 4Zn + 10HNO 4Zn(NO3)2 + NH4NO3 + 3H2O
      (very dilute)
       
    8. 4Zn + 10HNO(dil)  4Zn(NO3)2 + N2O + 5H2O
       
    9. 4Fe + 10HNO3  4Fe(NO3)2 + NH4NO3 + 3H2O
      (very dilute)
       
    10. 4Sn + 10HNO3  4Sn(NO3)2 + NH4NO+ 3H2O
      (dil.)
       
    11. Fe + 6HNO Fe(NO3)3 + 3NO2 + 3H2O
       (conc.)
       
    12. Sn + 4HNO H2SnO+ H2O + 4NO2
      (conc.)

    Reaction with non-metals, metalloids and compounds

    1. C + 4HNO3  CO2 + 4NO+ 2H2O
       
    2. S + 6HNO H2SO4 + 6NO2 + 2H2O
       
    3. l2 + 10HNO3  2HIO3 + 10NO2 + 2H2O
       
    4. B + 3HNO3  H3BO3 + 3NO2
       
    5. As + 5HNO3  H3AsO4 + 5NO2 + H2O
       
    6. Sb + 5HNO3  H3SbO4 + H2O + 5NO2
       
    7. SO2 + 2HNO3  H2SO4 + 2NO + O2
       
    8. 2Hl + 2HNO3  2NO+ 3l+ 2H2O
       
    9. 6FeSO4 + 3H2SO+ 2HNO 3Fe2(SO4)3 + 2NO + 4H2O


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