# 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) ${H}_{2}S$ is more acidic than ${H}_{2}O$.

(ii) $N{H}_{3}$ is more basic than $P{H}_{3}$.

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

(a) According to Le Chatelier's principle the favourable conditions for the production of $N{H}_{3}$ by Haber's process are

i) pressure of 200 atmosphere

ii) temperature of $~$700 K

iii) use of catalyst like $F{e}_{2}{O}_{3}$ with small amount of ${K}_{2}O$ and $A{l}_{2}{O}_{3}$

${N}_{2}+3{H}_{2}⇋2N{H}_{3}$

(b) (i) ${H}_{2}S$ is more acidic than ${H}_{2}O$ because bond dissociation enthalpy of H-S bond in ${H}_{2}S$ is less than that of H-O bond in ${H}_{2}O.$

(ii) Since both P and N contain lone pairs of electrons but due to small size and high electronegativity of Nitrogen in $N{H}_{3},$ the electron density is much higher than $P{H}_{3}$, therefore it can easily donate electrons and acts as strong Lewis base than $P{H}_{3}.$

(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:

Crack NEET with Online Course - Free Trial (Offer Valid Till August 27, 2019)