H3PO4 (aq) + 3 NaOH (aq) → 3 H2O (ℓ) + Na3PO4 (aq)

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Reaction Type:

Double Displacement

Stoichiometry

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H3PO4          Mass: g  or Solution Volume: mL of Concentration: mol/L
NaOH           Mass: g  or Solution Volume: mL of Concentration: mol/L
H2O            Mass: g
Na3PO4         Mass: g
Heat Released: kJ

Enthalpy of Reaction

[3ΔHf(H2O (ℓ)) + 1ΔHf(Na3PO4 (aq))] - [1ΔHf(H3PO4 (aq)) + 3ΔHf(NaOH (aq))]
[3(-285.83) + 1(-1997.68)] - [1(-1277.38) + 3(-470.09)] = -167.52 kJ
-167.52 kJ     (exothermic)

Entropy Change

[3ΔSf(H2O (ℓ)) + 1ΔSf(Na3PO4 (aq))] - [1ΔSf(H3PO4 (aq)) + 3ΔSf(NaOH (aq))]
[3(69.91) + 1(-44.75)] - [1(-221.75) + 3(48.25)] = 241.98 J/K
241.98 J/K     (increase in entropy)

Free Energy of Reaction (at 298.15 K)

From ΔGf° values:
[3ΔGf(H2O (ℓ)) + 1ΔGf(Na3PO4 (aq))] - [1ΔGf(H3PO4 (aq)) + 3ΔGf(NaOH (aq))]
[3(-237.18) + 1(-1804.5)] - [1(-1018.8) + 3(-419.18)] = -239.7 kJ
-239.70 kJ     (spontaneous)

From ΔG = ΔH - TΔS:
-239.67 kJ     (spontaneous)

Equilibrium Constant, K (at 298.15 K)

9.9074026803e+041
This process is favorable at 25°C.