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    I need to calculate the the enthalpy change for following reactions:

    (1) CH4(g) -> C(g) + 4H(g)

    (2) CH4(g) -> C(graphite) + 2H2(g)

    Then create a sublimation diagram to calculation the sublimation warmth for C(graphite). I know that to calculate this you need to take the sum of the formation enthalpies of the products and then substract the formation enthalpies of the reactions. But the catch is I don't know the formation enthalpy for carbon in a gaseous state and cannot find it in my formulary.
    For the second reaction I know it would be: delta H = 0 + (2x0) - (-74.6) = 74.6 kJ/mol.

    Is there any way I could calculate that value, because we can only use the values used in our formulary or we need to calculate them.

    Any help would be appreciated

    Here you go:

    Substance DHat/kJmol-1 C(graphite) +713 This is from A-level Chemistry website.

    And can you break down what you did in the second equation please? I don't get what you did? I think you took graphite to be 0, correct?
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