Given reaction:
H2(g) + Cl2(g) → 2HCl(g)
Formula:
Heat of the reaction is the enthalpy change given as:
ΔHrxn = ∑nΔH°f(products) - ∑nΔH°f(reactants)
= [2ΔH°f(HCl(g))] - [ΔH°f(H2(g)) + ΔH°f(Cl2(g))]
= [2(-92.31)] - [0 + 0] = -184.62 kJ/mol
The heat of the reaction is -184.62 kJ/mol