Hello candidate,

The standard heat of formation refers to the addition of all the individual specific heat of enthalpy for individual component and placing it in a balanced way so that the it leads to a balanced chemical reaction. So, the addition of carbon dioxide and water in appropriate proportions give rise to the formation of methane and upon calculation the heat of formation comes out to be 8.7 kk.

Hope you found it helpful. If you have any further queries feel free to post it here!!