MCQ
Consider the reactions given below. On the basis of these reactions find out which of the algebric relations given in options $(i)$ to $(iv)$ is correct?
  1. $\text{C}(\text{g})+4\text{H}(\text{g})\rightarrow\text{CH}_4(\text{g});\Delta_\text{r}\text{H}=\text{x}\text{kJ}\ \text{mol}^{-1}$
  2. $\text{C}(\text{graphite,s})+2\text{H}_2(\text{g})\rightarrow\text{CH}_4(\text{g});\Delta_\text{r}\text{H}=\text{y}\text{kJ}\ \text{mol}^{-1}$​​​​
  • A
    $\text{x}=\text{y}$
  • B
    $\text{x}=2\text{y}$
  • $\text{x} > \text{y}$
  • D
    $\text{x} < \text{y}$

Answer

Correct option: C.
$\text{x} > \text{y}$
$x > y$ because same bonds are formed in reactions $(i)$ and $(ii)$ but bonds between reactant molecules are broken only in reaction $(ii)$. As energy is absorbed when bonds are broken, energy released in reaction $(i)$ is greater than that in reaction $(ii).$

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