Average $\mathrm{C}-\mathrm{H}$ bond energy is $416 \mathrm{~kJ} \mathrm{~mol}^{-1}$. Which of the following…

Average $\mathrm{C}-\mathrm{H}$ bond energy is $416 \mathrm{~kJ} \mathrm{~mol}^{-1}$. Which of the following is correct?
  1. $\mathrm{CH}_4(g)+416 \mathrm{~kJ} \longrightarrow \mathrm{C}(g)+4 \mathrm{H}(g)$
  2. $\mathrm{CH}_4(g) \longrightarrow \mathrm{C}(g)+4 \mathrm{H}(g)+416 \mathrm{~kJ}$
  3. $\mathrm{CH}_4(g)+1664 \mathrm{~kJ} \longrightarrow \mathrm{C}(g)+4 \mathrm{H}(g)$
  4. $\mathrm{CH}_4(g) \longrightarrow \mathrm{C}(g)+4 \mathrm{H}(g)+1664 \mathrm{~kJ}$

Solution

$\mathrm{CH}_4$ has four $\mathrm{C}-\mathrm{H}$ bonds. So, $4 \times 416=1664 \mathrm{~kJ}$ is required to break $\mathrm{CH}_4$ into $\mathrm{C}$ and $4 \mathrm{H}$.

Asked in: AP EAMCET 2004

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