Q.
Using the data provided, calculate the multiple bond energy $\left(\right.kJmol^{- 1}\left.\right)$ of a $C\equiv C$ bond in $C_{2}H_{2}$ . That energy is (take the bond energy of a $C-H$ bond as $350 \, kJ$ $mol^{- 1}$ ).
$2C\left(s\right)+H_{2}\left(g\right) \rightarrow C_{2}H_{2}\left(g\right)\Delta H=225$ $kJmol^{- 1}$
$2C\left(\right.s\left.\right) \rightarrow 2C\left(\right.g\left.\right)\Delta H=1410$ $kJmol^{- 1}$
$H_{2}\left(g\right) \rightarrow 2H\left(g\right)\Delta H=330$ $kJmol^{- 1}$
NTA AbhyasNTA Abhyas 2022
Solution:
Let x be the bond energy of $C\equiv C$ , it can be find out as follows
$2C\left(\right.s\left.\right)+H_{2}\left(\right.g\left.\right) \rightarrow C_{2}H_{2}\left(\right.g\left.\right)$
$\Delta H=\Sigma \left[\left(B . E .\right)_{r e a c t a n t} - \left(B . E .\right)_{p r o d u c t} \right]$
$1410+330-\left(x + 2 \times 350\right)=225$
$x=815$ $kJmol^{- 1}$
$2C\left(\right.s\left.\right)+H_{2}\left(\right.g\left.\right) \rightarrow C_{2}H_{2}\left(\right.g\left.\right)$
$\Delta H=\Sigma \left[\left(B . E .\right)_{r e a c t a n t} - \left(B . E .\right)_{p r o d u c t} \right]$
$1410+330-\left(x + 2 \times 350\right)=225$
$x=815$ $kJmol^{- 1}$