Chemistry - Thermochemistry Question with Solution | TestHub
The enthalpies of formation of SO2(g), H2O(l), HCl(g) and H2SO4(l) are -70.97, -68.32, -22.1 and -188.84 (kcal/mol). The enthalpies of solution of SO2, H2SO4 and HCl in dilute solution are -8.56, -22.05 and -17.63 (kcal/mol), respectively. What is the enthalpy change for the reaction?
SO2(aq) + Cl2(g) + 2H2O(l) → H2SO4(aq) + 2HCl(aq)
Options:
Answer:
Solution:
The enthalpy of formation (Δ Hf) in solution is calculated as follows:
For SO₂(aq): -70.97 - 8.56 = -79.53 kcal/mol.
For H₂SO₄(aq): -188.84 - 22.05 = -210.89 kcal/mol.
For HCl(aq): -22.1 - 17.63 = -39.73 kcal/mol.
The enthalpy of reaction (Δ Hrxn) is calculated using the formula:
Δ Hrxn = Σ Δ Hf(products) - Σ Δ Hf(reactants)
Given the values, the calculation is:
Δ Hrxn = [-210.89 + 2(-39.73)] - [-79.53 + 2(-68.32)]
Δ Hrxn = [-210.89 - 79.46] - [-79.53 - 136.64]
Δ Hrxn = [-290.35] - [-216.17]
Δ Hrxn = -290.35 + 216.17 = -74.18 kcal
This corresponds to option (a).
