Consider the following data: s(s) + o2(g) → so2(g)    δhrxn = -297 kj 2so3(g) → 2so2(g) + o2(g)  δhrxn = 198 kj use hess's law to determine ^hrxn for this reaction: 2s(s) + 3o2(g) > 2so3(g) ^hrxn = ?

-792 KJ.

Explanation:

To get ΔH of the reaction: 2S + 3O₂ → 2SO₃ The sum of the two mentioned equations should give the result of the reaction we need to calculate its ΔH.We multiply the first equation by 2 and also its ΔHrxn:

2S + 2O₂ → 2SO₂             ΔHrxn = -594 KJ

and reverse the second reaction and so, multiply the ΔHrxn by -1:

2SO₂ + O₂ → 2SO₃          ΔHrxn = -198 KJ

By summing the two reactions, we get the reaction that we need to calculate its ΔHrxn: 2S + 3O₂ → 2SO₃ Now, we can apply Hess's law says that ΔH is a state function that do not depend on the path of the reaction but depends on the initial and final state.ΔHrxn = ΔH of the first reaction + ΔH of the second reaction ΔHrxn = (-594 KJ) + (-198 KJ) = -792 KJ.