The enthalpies of formation of H 2 S(g) and HI(g) are -4.9 and +6.3 kcal/mol, respectively. The enthalpies of solution of H 2 S and HI in dilute solution are -4.6 and -19.8 kcal/mol, respectively. Wha

Question

The enthalpies of formation of H 2 S(g) and HI(g) are -4.9 and +6.3 kcal/mol, respectively. The enthalpies of solution of H 2 S and HI in dilute solution are -4.6 and -19.8 kcal/mol, respectively. What is the enthalpy change for the reaction? H 2 S(aq) + I 2 (s) → 2HI(aq) + S(s)

TestHub · Accepted Answer

Δ f H in solution: H 2 S(aq) = -4.9 - 4.6 = -9.5; HI(aq) = +6.3 - 19.8 = -13.5 kcal/mol. Elements I 2 (s) and S(s) are zero. ΔH rxn = [2(-13.5)] - [-9.5] = -27.0 + 9.5 = -17.5 kcal. This is option (b).

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