## Ca3(PO4)2 (s beta) + 3 H2SO4 (ℓ) → 2 H3PO4 (ℓ) + 3 CaSO4 (s)

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## Stoichiometry

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 Ca3(PO4)2      Mass: g H2SO4          Mass: g H3PO4          Mass: g CaSO4          Mass: g Heat Released: kJ

## Enthalpy of Reaction

[2ΔHf(H3PO4 (ℓ)) + 3ΔHf(CaSO4 (s))] - [1ΔHf(Ca3(PO4)2 (s beta)) + 3ΔHf(H2SO4 (ℓ))]
[2(-1254.36) + 3(-1434.5)] - [1(-4120.82) + 3(-814)] = -249.4 kJ
-249.40 kJ     (exothermic)

## Entropy Change

[2ΔSf(H3PO4 (ℓ)) + 3ΔSf(CaSO4 (s))] - [1ΔSf(Ca3(PO4)2 (s beta)) + 3ΔSf(H2SO4 (ℓ))]
[2(150.62) + 3(106.5)] - [1(235.98) + 3(156.9)] = -85.9400000000001 J/K
-85.94 J/K     (decrease in entropy)

## Free Energy of Reaction (at 298.15 K)

From ΔGf° values:
[2ΔGf(H3PO4 (ℓ)) + 3ΔGf(CaSO4 (s))] - [1ΔGf(Ca3(PO4)2 (s beta)) + 3ΔGf(H2SO4 (ℓ))]
[2(-1111.69) + 3(-1322)] - [1(-3884.84) + 3(-690.07)] = -234.33 kJ
-234.33 kJ     (spontaneous)

From ΔG = ΔH - TΔS:
-223.78 kJ     (spontaneous)

## Equilibrium Constant, K (at 298.15 K)

1.1353353741e+041
This process is favorable at 25°C.

## Reference(s):

Zumdahl, Steven and Zumdahl, Susan A. Chemistry 9th ed.; Brooks/Cole: Belmont, CA, 2014; p 133.