Compute the ƒ´Hrxn for the following:
CH3OH „³ H2CO + H2
Carbon is the central atom on both the starting material and the product.
I don't understand all of the symbols used in your post but
dHrxn = (n*dHf products) - (n*dHf reactants)
You should be able to find dHformation in tables in your text.