The reaction that shows that the enthalpy of formation of CS2 is H89.4 kj mol is:

C(s) + 2S(s) → CS2(l) ΔH = +89.4 kJ/mol

This reaction shows that when one mole of carbon and two moles of sulfur react to form one mole of carbon disulfide, 89.4 kJ of heat is released. This means that the enthalpy of formation of CS2 is +89.4 kJ/mol.