6 HNO3 (aq) + S (s rhombic) → 6 NO2 (g) + H2SO4 (aq) + 2 H2O (ℓ)

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Stoichiometry

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HNO3           Mass: g  or Solution Volume: mL of Concentration: mol/L
S              Mass: g
NO2            Mass: g  or Gas Volume: L
H2SO4          Mass: g
H2O            Mass: g
Heat Released: kJ

Enthalpy of Reaction

[6ΔHf(NO2 (g)) + 1ΔHf(H2SO4 (aq)) + 2ΔHf(H2O (ℓ))] - [6ΔHf(HNO3 (aq)) + 1ΔHf(S (s rhombic))]
[6(33.18) + 1(-909.27) + 2(-285.83)] - [6(-207.36) + 1(0)] = -37.6899999999998 kJ
-37.69 kJ     (exothermic)

Entropy Change

[6ΔSf(NO2 (g)) + 1ΔSf(H2SO4 (aq)) + 2ΔSf(H2O (ℓ))] - [6ΔSf(HNO3 (aq)) + 1ΔSf(S (s rhombic))]
[6(239.95) + 1(20.08) + 2(69.91)] - [6(146.44) + 1(31.92)] = 689.04 J/K
689.04 J/K     (increase in entropy)

Free Energy of Reaction (at 298.15 K)

From ΔGf° values:
[6ΔGf(NO2 (g)) + 1ΔGf(H2SO4 (aq)) + 2ΔGf(H2O (ℓ))] - [6ΔGf(HNO3 (aq)) + 1ΔGf(S (s rhombic))]
[6(51.3) + 1(-744.63) + 2(-237.18)] - [6(-111.34) + 1(0)] = -243.15 kJ
-243.15 kJ     (spontaneous)

From ΔG = ΔH - TΔS:
-243.13 kJ     (spontaneous)

Equilibrium Constant, K (at 298.15 K)

3.9848070462e+042
This process is favorable at 25°C.