The standard enthalpy of formation of propane gas, C ₃ H ₈( g ) , is -104 kJ mol ⁻¹ . The standard enthalpies of combustion of graphite and hydrogen gas are -394 kJ mol ⁻¹ and -286 kJ mol ⁻¹ respectively. The magnitude of the standard enthalpy of combustion of C ₃ H ₈( g ) is _______ kJ mol ⁻¹ (Nearest integer).

Step-by-step solution

The balanced chemical equation for the combustion of propane is: C ₃ H ₈( g ) + 5 O ₂( g ) 3 CO ₂( g ) + 4 H ₂ O ( l ) The standard enthalpy of combustion is given by: H _c^ = H _f^ ( products ) - H _f^ ( reactants ) The standard enthalpy of combustion of graphite is the standard enthalpy of formation of CO ₂( g ) , so H _f^ ( CO ₂) = -394 kJ mol ⁻¹ . The standard enthalpy of combustion of hydrogen gas is the standard enthalpy of formation of H ₂ O ( l ) , so H _f^ ( H ₂ O ) = -286 kJ mol ⁻¹ . Substituting the valu