KVPY Sample Paper KVPY Stream-SX Model Paper-24

The heat of atomisation of \[P{{H}_{3}}\left( g \right)\] and \[{{P}_{2}}{{H}_{4}}\left( g \right)\]are 953 and \[1485\,kJ\,mo{{l}^{-1}}\] respectively. The \[P-P\] bond energy in kJ \[mo{{l}^{-1}}\] is

A) 214

B) 426

C) 318

D) 1272

Correct Answer: A

Solution :

\[P{{H}_{3}}\left( g \right)\xrightarrow{{}}p\left( g \right)+3H\left( g \right)\]

\[\Delta H=953\,kJ\,mo{{l}^{-1}}\]

BE of \[\left( P-H \right)bond=\frac{953}{3}\]

\[{{P}_{2}}{{H}_{4}}\left( g \right)\xrightarrow{{}}2P\left( g \right)+4H\left( g \right)\]

This involve breaking of one \[(P-P)\] bond and four \[(P-H)\] bonds.

\[\therefore \,\,\Delta H=\frac{953}{3}\times 4+BE\left( P-P \right)\]

\[1485=\frac{953}{3}\times 4+BE\left( p-p \right)\]

\[BE\left( P-P \right)=214.3kJ\]