2 H3PO4 (aq) + 3 MgCO3 (s) → Mg3(PO4)2 (s) + 3 H2O (ℓ) + 3 CO2 (g)

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Reaction Type:

Double Displacement/Decomposition of a Carbonate

Stoichiometry

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Heat Added: kJ
H3PO4          Mass: g  or Solution Volume: mL of Concentration: mol/L
MgCO3          Mass: g
Mg3(PO4)2      Mass: g
H2O            Mass: g
CO2            Mass: g  or Gas Volume: L

Enthalpy of Reaction

[1ΔHf(Mg3(PO4)2 (s)) + 3ΔHf(H2O (ℓ)) + 3ΔHf(CO2 (g))] - [2ΔHf(H3PO4 (aq)) + 3ΔHf(MgCO3 (s))]
[1(-3780.66) + 3(-285.83) + 3(-393.51)] - [2(-1277.38) + 3(-1095.79)] = 23.4500000000007 kJ
23.45 kJ     (endothermic)

Entropy Change

[1ΔSf(Mg3(PO4)2 (s)) + 3ΔSf(H2O (ℓ)) + 3ΔSf(CO2 (g))] - [2ΔSf(H3PO4 (aq)) + 3ΔSf(MgCO3 (s))]
[1(189.2) + 3(69.91) + 3(213.68)] - [2(-221.75) + 3(65.69)] = 1286.4 J/K
1,286.40 J/K     (increase in entropy)

Free Energy of Reaction (at 298.15 K)

From ΔGf° values:
[1ΔGf(Mg3(PO4)2 (s)) + 3ΔGf(H2O (ℓ)) + 3ΔGf(CO2 (g))] - [2ΔGf(H3PO4 (aq)) + 3ΔGf(MgCO3 (s))]
[1(-3538.83) + 3(-237.18) + 3(-394.38)] - [2(-1018.8) + 3(-1012.11)] = -359.58 kJ
-359.58 kJ     (spontaneous)

From ΔG = ΔH - TΔS:
-360.09 kJ     (spontaneous)

Equilibrium Constant, K (at 298.15 K)

9.9814994582e+062
This process is favorable at 25°C.