KVPY Sample Paper KVPY Stream-SX Model Paper-20

The heats of atomization of \[P{{H}_{3}}(g)\] and \[{{P}_{2}}{{H}_{4}}(g)\] are \[954 kJ mo{{l}^{-1}}\] and \[1485 kJ mo{{l}^{-1}}\] respectively. The P-P bond energy in \[\operatorname{kJ} mo{{l}^{-1}}\]is

A) 213

B) 426

C) 318

D) 1272

Correct Answer: A

Solution :

In \[P{{H}_{3}}(g),\] energy required to break 3P-H bonds \[=954kJmo{{l}^{-1}}\]

\[\therefore \]Energy required to break 1P-Hbond \[=\frac{954}{3}=318kJmo{{l}^{-1}}\]

In \[{{\operatorname{P}}_{2}}{{H}_{4}}\left( g \right),\]energy of 1 P-P bond +4 P-H bonds\[=1485kJmo{{l}^{-1}}\]

\[\because \]Energy of 1 P- H bond \[=318kJmo{{l}^{-1}}\]

\[\because \]Energy of 4 P- H bond \[=318\times 4\]\[=1272kJmo{{l}^{-1}}\]

Thus, the P-P bond energy \[=1485-1272\]\[=213kJmo{{l}^{-1}}\]