Question

The dissociation energy of $CH _{4}$ and $C _{2} H _{6}$ to convert them into gaseous atoms are $360$ and $620 \,kcal / mol$ respectively. The bond energy of $C - C$ bond is

• A. $130\,kcal / mol$
• B. $80 \,kcal / mol$
• C. $180 \,kcal / mol$
• D. $260\,kcal / mol$

Answer 1

Answer: (B)

$CH _{4(g)} \rightarrow C _{(g)}+4 H _{(g)} ; \quad \Delta H_{1}=360\, kcal / mol$

$C _{2} H _{6(g)} \rightarrow 2 C _{(g)}+6 H _{(g)} ; \Delta H_{2}=620\, kcal / mol$

$\Delta H_{2}=6 \times \frac{\Delta H_{1}}{4}+\Delta H_{ C - C }$

$\Delta H_{ C - C }=620-\left(\frac{360}{4}\right) 6=80\, kcal / mol$