Question

Use standard enthalpies of formation to calculate ΔH∘rxn for the following reaction: SO2(g)+12O2(g)→SO3(g) : C(s)+H2O(g)→CO(g)+H2(g) : N2O4(g)+4H2(g)→N2(g)+4H2O(g)

Answer 1

Solution :-

Formula to calculate the Delta H reaction is as follows

Delta H rxn = sum of delta H of product – sum of delta H of reactant

SO2(g)+12O2(g)→SO3(g)

Delta H rxn = sum of delta H of product – sum of delta H of reactant

                     = [SO3*1] – [SO2*1]

                     = [-396*1]-[-296.8*1]

                     = -99.2 kJ

Oxygen is not involved because standard enthalpy of formation of the oxygen is 0 kJ/mol

C(s)+H2O(g)→CO(g)+H2(g)

Delta H rxn = sum of delta H of product – sum of delta H of reactant

                    = [(CO*1)+(H2*1)] –[ (C*1)+(H2O*1)]

                   = [(-110.5*1)+(0*1)]-[(-241.8*1)+(0*1)]

                   = 131.3 kJ

N2O4(g)+4H2(g)→N2(g)+4H2O(g)

Delta H rxn = sum of delta H of product – sum of delta H of reactant

                     = [(N2*1)+(H2O*4)]-[(N2O4*1)+(H2*4)]

                     =[(0*1)+(-241.8*4)] –[ (9.16*1)+(0*4)]

                     = -976.36 kJ