## 2 B5H9 (ℓ) + 12 O2 (g) → 5 B2O3 (s) + 9 H2O (g)

Back to reactions list

## 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.

 B5H9           Mass: g O2             Mass: g or Gas Volume: L B2O3           Mass: g H2O            Mass: g or Gas Volume: L Heat Released: kJ

## Enthalpy of Reaction

[5ΔHf(B2O3 (s)) + 9ΔHf(H2O (g))] - [2ΔHf(B5H9 (ℓ)) + 12ΔHf(O2 (g))]
[5(-1272.77) + 9(-241.82)] - [2(42.68) + 12(0)] = -8625.59 kJ
-8,625.59 kJ     (exothermic)

## Entropy Change

[5ΔSf(B2O3 (s)) + 9ΔSf(H2O (g))] - [2ΔSf(B5H9 (ℓ)) + 12ΔSf(O2 (g))]
[5(53.97) + 9(188.72)] - [2(184.22) + 12(205.03)] = -860.47 J/K
-860.47 J/K     (decrease in entropy)

## Free Energy of Reaction (at 298.15 K)

From ΔGf° values:
[5ΔGf(B2O3 (s)) + 9ΔGf(H2O (g))] - [2ΔGf(B5H9 (ℓ)) + 12ΔGf(O2 (g))]
[5(-1193.7) + 9(-228.59)] - [2(171.67) + 12(0)] = -8369.15 kJ
-8,369.15 kJ     (spontaneous)

From ΔG = ΔH - TΔS:
-8369.04 kJ     (spontaneous) ## Equilibrium Constant, K (at 298.15 K)

approaches infinity
This process is favorable at 25°C.

## Reference(s):

Zumdahl, Steven and Zumdahl, Susan A. Chemistry 9th ed.; Brooks/Cole: Belmont, CA, 2014; p 134.