The standard heat of formation `(Delta_(f)H_(298)^(0))` of ethane (in kJ/mol), if the heat of combustion of ethane, hydrogen and graphite are `-1560, -393.5` and `-286kJ/mol`, respectively is _______.

Answer

`-192.5`

Explanation

`2C(s) + 3H_(2)(g) rarr C_(2)H_(6)(g)`
`DeltaH_(f)^(@) (C_2H_6) = sum Delta H_(C )^(@)("reactants") - sum Delta H_(C )^(@) ("products")`
`=2 xx Delta H_(C )^(@)C (s) + 3Delta H_(C )^(@)H_(2)(g) - Delta H_(C )^(@) C_(2)H_(6) (g)`
`=2 xx (-286) + 3 xx (-393.5) - (-1560)`
`=-192.5 kJ`