The standard enthalpy of formation ( Δ f H ∘ 298 ) for methane, CH 4 is − 74.9 kJ mol − 1 . In order to calculate the average energy given out in the formation of a C − H bond from this it is ne

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The standard enthalpy of formation ( Δ f ​ H ∘ 298 ​ ) for methane, CH 4 ​ is − 74.9 kJ mol − 1 . In order to calculate the average energy given out in the formation of a C − H bond from this it is necessary to know which one of the following?

TestHub · Accepted Answer

To calculate average enthalpy of C − H bond in methane following informations are needed (i) dissociation energy of H 2 ​ i.e. 2 1 ​ H 2 ​ ( g ) ⟶ H ( g ) ; Δ H = x ( suppose ) (ii) Sublimation energy of C (graphite) to C ( g ) C ( graphite ) ⟶ C ( g ) ; Δ H = y (Suppose) Given C ( graphite ) + 2 H 2 ​ ( g ) ⟶ CH 4 ​ ( g ) ; Δ H = 75 kJ mol − 1

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