## 3 As (s alpha-gray) + 5 HNO3 (aq) + 2 H2O (ℓ) → 3 H3AsO4 (aq) + 5 NO (g)

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## Stoichiometry

Enter a mass or volume in one of the boxes below. Upon hitting submit, the stoichiometric equivalents will be calculated for the remaining reactants and products. All gases are assumed to be at STP.

 As             Mass: g HNO3           Mass: g or Solution Volume: mL of Concentration: mol/L H2O            Mass: g H3AsO4         Mass: g NO             Mass: g or Gas Volume: L Heat Released: kJ

## Enthalpy of Reaction

[3ΔHf(H3AsO4 (aq)) + 5ΔHf(NO (g))] - [3ΔHf(As (s alpha-gray)) + 5ΔHf(HNO3 (aq)) + 2ΔHf(H2O (ℓ))]
[3(-888.1) + 5(90.25)] - [3(0) + 5(-207.36) + 2(-285.83)] = -604.59 kJ
-604.59 kJ     (exothermic)

## Entropy Change

[3ΔSf(H3AsO4 (aq)) + 5ΔSf(NO (g))] - [3ΔSf(As (s alpha-gray)) + 5ΔSf(HNO3 (aq)) + 2ΔSf(H2O (ℓ))]
[3(-162.8) + 5(210.65)] - [3(35.15) + 5(146.44) + 2(69.91)] = -412.62 J/K
-412.62 J/K     (decrease in entropy)

## Free Energy of Reaction (at 298.15 K)

From ΔGf° values:
[3ΔGf(H3AsO4 (aq)) + 5ΔGf(NO (g))] - [3ΔGf(As (s alpha-gray)) + 5ΔGf(HNO3 (aq)) + 2ΔGf(H2O (ℓ))]
[3(-648.4) + 5(86.57)] - [3(0) + 5(-111.34) + 2(-237.18)] = -481.29 kJ
-481.29 kJ     (spontaneous)

From ΔG = ΔH - TΔS:
-481.57 kJ     (spontaneous)

## Equilibrium Constant, K (at 298.15 K)

2.1040290348e+084
This process is favorable at 25°C.