4.8 g of C (diamond) on complete combustion evolves 1584 kJ of heat. The standard heat of formation of gaseous carbon is 725 kJ/mol. The energy required for the process(i) C(graphite) →  C(gas)(ii) C(diamond) →  C(gas) are

The expression for standard heat of formation of gaseous carbon isC(graphite) →  C(gas)∆H=725 kJ/molAs graphite is thermodynamically more stable than diamond so the heat required to convert graphite to gaseous carbon should be more.