Problem: The methane molecule, CH4, has the geometry shown in following figure. Imagine a hypothetical process in which the methane molecule is "expanded," by simultaneously extending all four C–H bonds to infinity. We then have the process CH4(g) → C(g) + 4 H(g).Calculate the enthalpy change of formation of CH4(g)

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We are asked to calculate the enthalpy change of formation of CH4(g)


ΔH°rxn=ΔH°f, product-ΔH°f,reactant


Note that we need to multiply each ΔH˚ by the stoichiometric coefficient since ΔH˚ is in kJ/mol. 


Balanced reaction : C(s) + 2 H2(g) CH4(g).

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Problem Details
The methane molecule, CH4, has the geometry shown in following figure. Imagine a hypothetical process in which the methane molecule is "expanded," by simultaneously extending all four C–H bonds to infinity. We then have the process CH4(g) → C(g) + 4 H(g).

The figure shows a ball-and-stick model and a perspective drawing of CH4.

Calculate the enthalpy change of formation of CH4(g)

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