If the combustion of 1 g of graphite produces -20. 7 kJ of heat, what will be molar enthalpy change ? Give the significance of sign also.

Explanation

Enthalpy of combustion of 1 g graphite= 20.7 kJ
Molar enthalpy change for the combustion of graphite `Delta H = ` enthalpy of combustion of 1g graphite `xx` molar mass
`Delta H = - 20.7 "kJ g"^(-1) xx 12 "g mol"^(-1)`
`Delta H = - 2.48 xx 10^(2) "kJ mol"^(-1)`
Negative sign in the value of `Delta H` indicates that the reaction is exothermic.