Question

The heat of reaction for the combustion of propane is –2,045 kJ. This reaction is: C3H8(g) +502 (g) 3CO2 (g) + 4H2O (g). Determine the standard heat of formation of propane.

Answer 1

`\Delta _fH_(C_3H_8)=-102.7kJ/mol`

Step-by-step explanation:

Hello,

In this case, we can consider that the given heat of combustion is indeed the heat of reaction since it corresponds to the combustion of propane, which is computed by using the heat formation of all the involved species as shown below:

`\Delta _cH=3*\Delta _fH_(CO_2)+4*\Delta _fH_(H_2O)-\Delta _fH_(C_3H_8)-5*\Delta _fH_(O_2)`

Thus, since the heat of formation of gaseous carbon dioxide is -393.5 kJ/mol, water -241.8 kJ/mol and oxygen 0 kJ/mol, the heat of formation of propane is:

`\Delta _fH_(C_3H_8)=3*\Delta _fH_(CO_2)+4*\Delta _fH_(H_2O)-5*\Delta _fH_(O_2)-\Delta _cH\\\\\Delta _fH_(C_3H_8)=3*(-393.5)+4*(-241.8)-5*0-(-2045)\\\\\Delta _fH_(C_3H_8)=-102.7kJ/mol`

Best regards.