NEET Chemistry The p-Block Elements (XII) Questions Solved

BOARD

(a) How is ammonia prepared on a large scale ? Name the process and mention the optimum conditions for the production of ammonia by this process.

(b) Assign reasons for the following :

(i) H2S is more acidic than H2O.

(ii) NH3 is more basic than PH3.

(iii) Sulphur has a greater tendency for catenation than oxygen.

(a) According to Le Chatelier's principle the favourable conditions for the production of NH3 by Haber's process are

i) pressure of 200 atmosphere 

ii) temperature of ~700 K

iii) use of catalyst like Fe2O3 with small amount of K2O and Al2O3

   N2+3H22NH3

(b) (i) H2S is more acidic than H2O because bond dissociation enthalpy of H-S bond in H2S is less than that of H-O bond in H2O.

(ii) Since both P and N contain lone pairs of electrons but due to small size and high electronegativity of Nitrogen in NH3, the electron density is much higher than PH3, therefore it can easily donate electrons and acts as strong Lewis base than PH3.

(iii) The greater catenation tendency of sulphur is due to two reasons :

1) The lone pair of electrons feels more repulsion in O-O bond than S-S bond due to its small size and thus S-S forms strong bond.

2) As the size of atom increases down the group from O-PO, the strength of bond increases and therefore catenation tendency also increases.

Difficulty Level:

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