(CN)2 (g cyanogen) + 4 H2O (ℓ) → H2C2O4 (aq) + 2 NH3 (g)

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Stoichiometry

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(CN)2          Mass: g
H2O            Mass: g
H2C2O4         Mass: g  or Solution Volume: mL of Concentration: mol/L
NH3            Mass: g  or Gas Volume: L

Enthalpy of Reaction

[1ΔHf(H2C2O4 (aq)) + 2ΔHf(NH3 (g))] - [1ΔHf((CN)2 (g cyanogen)) + 4ΔHf(H2O (ℓ))]
[1(-825.1) + 2(-46.11)] - [1(308.95) + 4(-285.83)] = -82.9500000000002 kJ
-82.95 kJ     (exothermic)

Entropy Change

[1ΔSf(H2C2O4 (aq)) + 2ΔSf(NH3 (g))] - [1ΔSf((CN)2 (g cyanogen)) + 4ΔSf(H2O (ℓ))]
[1(45.6) + 2(192.34)] - [1(242.25) + 4(69.91)] = -91.61 J/K
-91.61 J/K     (decrease in entropy)

Free Energy of Reaction (at 298.15 K)

From ΔGf° values:
[1ΔGf(H2C2O4 (aq)) + 2ΔGf(NH3 (g))] - [1ΔGf((CN)2 (g cyanogen)) + 4ΔGf(H2O (ℓ))]
[1(-673.9) + 2(-16.48)] - [1(297.19) + 4(-237.18)] = -55.33 kJ
-55.33 kJ     (spontaneous)

From ΔG = ΔH - TΔS:
-55.64 kJ     (spontaneous)

Equilibrium Constant, K (at 298.15 K)

4942378355.19166
This process is favorable at 25°C.

Reference(s):

Silberberg, Martin S. Chemistry: The Molecular Nature of Matter and Change 4th ed.; McGraw-Hill: Boston, MA, 2006; p 127.

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