Question

The bond dissociation energies of $H-H,C-C$ and $C-H$ bonds respectively are $104.2,83.1$ and $98.8$ kcal $mo{l}^{-1}$. The electronegativity of carbon is:

• A. $2.53$
• B. $2.51$
• C. $2.57$
• D. $2.52$

Answer 1

Answer: (C)

$2.57$

Given bond dissociation energies :

$E(H-H)=104.2$ Kcal/mol

$E(C-C)=83.1$ Kcal/mol

$E(C-H)=98.8$ Kcal/mol

Difference in electronegativity of carbon and hydrogen given by :

$X_C-X_H={\left(eV\right)}^{1/2}\sqrt{E_{(C-H)}-\frac{E_{C-C}+E_{H-H}}{2}}$

w.k.t, $X_H=2.1$ standard value of hydrogen electronegativity also, $V=$

$\Rightarrow X_C-2.1=\left(0.208\right)\sqrt{98.8-\frac{104.2+83.1}{2}}$

$\Rightarrow X_C-2.1=\left(0.208\right)\left(2.2694\right)$

$\Rightarrow X_C=2.572$ is required electronegativity of carbon.