Answer to Question #142742 in Physical Chemistry for Haggy

Question

Give the precise thermochemical equation to which the following statements refer.
(i) The standard enthalpy of formation Of methane is - 74.8 K J/mol
(ii) The mean bond energy of C - H bond in methane is 413 KJ/mol
(iii) The enthalpy of atomization of carbon is 715 KJ/mol

Answer 1

(i) C_{(solid, graphite)} + 2H2_(gas) = CH4_(gas) $\Delta$_fH^o = -74 kJ/mol

(ii) 1/4CH4_(gas) = 1/4C_(gas) + H_(gas) $\Delta$_rH = 413 kJ/mol

(iii) C_{(solid, graphite)} = C_(gas) $\Delta$_atomH = 715 kJ/mol