Question

Enthalpy for the oxidation of graphite to CO₂ and CO to CO₂ can easily be measured. For these conversions, the heat of combustion values are -393.5 kJ and -283.5 kJ respectively.

Answer 1

From these data the enthalpy of combustion of graphite to CO can be calculated by applying Hess’s law. The reactions involved in this process can be expressed as follows:

According to Hess law, 

∆H₁ = ∆H₂ + ∆H₃ 

-393.5 kJ = X – 283.5 kJ 

X = – 110.5 kJ