## CaF2 (s) + 1 H2SO4 (ℓ) → 2 HF (g) + CaSO4 (s)

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## Reaction Type:

Double Displacement

## Stoichiometry

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 Heat Added: kJ CaF2           Mass: g H2SO4          Mass: g HF             Mass: g or Gas Volume: L CaSO4          Mass: g

## Enthalpy of Reaction

[2ΔHf(HF (g)) + 1ΔHf(CaSO4 (s))] - [1ΔHf(CaF2 (s)) + 1ΔHf(H2SO4 (ℓ))]
[2(-271.12) + 1(-1434.5)] - [1(-1219.64) + 1(-814)] = 56.9000000000001 kJ
56.90 kJ     (endothermic)

## Entropy Change

[2ΔSf(HF (g)) + 1ΔSf(CaSO4 (s))] - [1ΔSf(CaF2 (s)) + 1ΔSf(H2SO4 (ℓ))]
[2(173.68) + 1(106.5)] - [1(68.87) + 1(156.9)] = 228.09 J/K
228.09 J/K     (increase in entropy)

## Free Energy of Reaction (at 298.15 K)

From ΔGf° values:
[2ΔGf(HF (g)) + 1ΔGf(CaSO4 (s))] - [1ΔGf(CaF2 (s)) + 1ΔGf(H2SO4 (ℓ))]
[2(-273.22) + 1(-1322)] - [1(-1167.34) + 1(-690.07)] = -11.0300000000002 kJ
-11.03 kJ     (spontaneous)

From ΔG = ΔH - TΔS:
-11.11 kJ     (spontaneous)

## Equilibrium Constant, K (at 298.15 K)

85.601213177
This process is favorable at 25°C.

## Reference(s):

Ebbing, Darrell D. General Chemistry 3rd ed.; Houghton Mifflin Company: Boston, MA, 1990; p 139.