Question

Calculate the enthalpy of formation of Benzene represented by following reaction
6C + 2H2 gives C6H6
The standard enthalpy of combustion of Benzene is -3266.0 kJ and standard enthalpy of formation of CO2 and H2O are -393.1 kJ and -286.0 kJ respectively.

Answer 1

This is quite simple, all you need to do is to re-read the question;

It goes that Calculate the enthalpy of formation of Benzene represented by following reaction  6C + 2H2 ⇒ C6H6  

The standard enthalpy of combustion of Benzene is -3266.0 kJ and standard enthalpy of formation of CO2 and H2O are -393.1 kJ and -286.0 kJ respectively.

then enthalpy of formation of C6H6 + dH combu C6H6= dHf H20 + dH CO2

-3266 + dHf = (6 x -393.1) + (2 x -286)

dHf = -2930.6 + 3266

dHf = + 335