A) The dissociation energy of the hydrogen molecule, \[{{H}_{2}}\].
B) The first four ionisation energies of carbon.
C) The dissociation energy of \[{{H}_{2}}\] and enthalpy of sublimation of carbon (graphite).
D) The first four ionisation energies of carbon and electron affinity of hydrogen.
Correct Answer: C
Solution :
[c] To calculate average enthalpy of \[C-H\] bond in methane following in formations are needed (i) (i) dissociation energy of \[{{H}_{2}}\] i.e. \[\frac{1}{2}{{H}_{2}}(g)\xrightarrow{{}}H(g);\Delta H=x(suppose)\] (ii) Sublimation energy of C(graphite) to C(g) \[C\left( graphite \right)\xrightarrow{{}}C\left( g \right);\text{ }\Delta H=y\left( Suppose \right)\] Given \[C(graphite)+2{{H}_{2}}(g)\xrightarrow{{}}C{{H}_{4}}(g);\] \[\Delta H=75\text{ }kJ\text{ }mo{{l}^{-1}}\]
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