Consider graphite and oxygen are allowed to react to form ca

Consider graphite and oxygen are allowed to react to form carbon dioxide in a steady state system at 298 K and 1 atm. Calculate the heat of formation of carbon dioxide. Experiment Q=-393.5KJ/mol. Please provide some explanation at the side for your working. [6]

Solution

C + O2 = CO2

The standard enthalpy of formation is measured in units of energy per amount of substance, usually stated in kilojoule per mole (kJ mol¹),

All elements in their standard states (oxygen gas, solid carbon in the form of graphite, etc.) have a standard enthalpy of formation of zero, as there is no change involved in their formation.

For any given reaction,

_rH = _fH^o_products - _fH^{o _reactants}

Therefore for the reaction:

Cs) + O₂(g) -------> CO₂(g)

_rH = [_fH^o(CO₂) ] - [_fH^o(C) + _fH^o(O₂)] = (-393.5) kJ