Question

Enthalpy of atomization of $C_{2}H_{6}\left(g\right)$ and $C_{3}H_{8}\left(g\right)$ are $620$ and $880kJmol^{- 1}$ respectively. The $\text{C} - \text{C}$ and $\text{C} - \text{H}$ bond energies are respectively

• A. $80$ and $60 kJmol^{- 1}$
• B. $80$ and $90kJmol^{- 1}$
• C. $70$ and $90kJmol^{- 1}$
• D. $200$ and $80kJmol^{- 1}$

Answer 1

Answer: (B)

$C _2 H _6( g ) \longrightarrow 2 C ( g )+6 H ( g )$
$\Delta H_{ C - C }+6 \Delta H_{ C - H }=620 kJ mol ^{-1} $
$ C _3 H _8( g ) \longrightarrow 3 C ( g )+8 H ( g ) $
$ 2 \Delta H_{ C - C }+8 \Delta H_{ C - H }=880 kJ mol ^{-1} $
$ \text { Hence, } \Delta H_{ C - C }=80 kJ mol ^{-1} $
$ \Delta H_{ C - H }=90 kJ mol ^{-1}$