Question

Consider the reactions:

$C\left(s\right)+2H_2\left(g\right)⟶C{H}_4\left(g\right);\Delta H=-Xkcal$

$C\left(g\right)+4H\left(g\right)⟶C{H}_4\left(g\right);\Delta H=-X_{1}kcal$

$C{H}_4\left(g\right)⟶C{H}_3\left(g\right)+H\left(g\right);\Delta H=+Ykcal$

The average bond energy of $C-H$ bond is:

• A. $\frac{X}{4}kcalmo{l}^{-1}$
• B. $Ykcalmo{l}^{-1}$
• C. $\frac{X_1}{4}kcalmo{l}^{-1}$
• D. $X_{1}kcalmo{l}^{-1}$

Answer 1

Answer: (C)

$\frac{X_1}{4}kcalmo{l}^{-1}$

The reaction for the formation of methane is as given below.

$C\left(g\right)+4H\left(g\right)⟶C{H}_4\left(g\right);\Delta H=-X_{1}kcal$

Its reverse will be the reaction for the dissociation of methane which will give the dissociation energy of methane.

Average bond energy of $C--H$ bond is

$\frac{DissociationenergyofC{H}_4}{No.ofbondbroken}=\frac{X_1}{4}$

Thus, the average bond energy of $C-H$ bond is $\frac{X_1}{4}kcalmo{l}^{-1}$.

Hence, the correct option is $C$.