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

BOARD

(a) Give reasons for the following :

(i) Bond enthalpy of ${F}_{2}$ is lower than that of $C{l}_{2}$.

(ii) $P{H}_{3}$ has lower boiling point than $N{H}_{3}$.

(b) Draw the structures of the following molecules :

(i) $CI{F}_{3}$                                 (ii) ${\left(HP{O}_{3}\right)}_{3}$                            (iii) $Xe{F}_{4}$

(a) (i) Due to smaller size of F than Cl as a result of which electron-electron repulsions between the lone pairs of electrons are very large than that of Cl, hence bond dissociation enthalpy of ${F}_{2}$ is less than that of $C{l}_{2}$.

(ii) $P{H}_{3}$ has lower boiling point than $N{H}_{3}$ because $P{H}_{3}$ cannot form hydrogen bonds like $N{H}_{3}$.

(b) (i) $CI{F}_{3}$ :

Shape : Bent T-shape

(ii) ${\left(HP{O}_{3}\right)}_{3}$ : Cyclotrimetaphosphoric acid

(iii) $Xe{F}_{4}$ :

Shape : Square planar

Difficulty Level: