## CaO (s) + 1 H2O (ℓ) → Ca+2 (aq) + 2 OH-1 (aq)

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## Stoichiometry

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 CaO            Mass: g H2O            Mass: g Ca+2           Mass: g OH-1           Mass: g Heat Released: kJ

## Enthalpy of Reaction

[1ΔHf(Ca+2 (aq)) + 2ΔHf(OH-1 (aq))] - [1ΔHf(CaO (s)) + 1ΔHf(H2O (ℓ))]
[1(-542.83) + 2(-229.99)] - [1(-635.13) + 1(-285.83)] = -81.85 kJ
-81.85 kJ     (exothermic)

## Entropy Change

[1ΔSf(Ca+2 (aq)) + 2ΔSf(OH-1 (aq))] - [1ΔSf(CaO (s)) + 1ΔSf(H2O (ℓ))]
[1(-53.14) + 2(-10.75)] - [1(38.2) + 1(69.91)] = -182.75 J/K
-182.75 J/K     (decrease in entropy)

## Free Energy of Reaction (at 298.15 K)

From ΔGf° values:
[1ΔGf(Ca+2 (aq)) + 2ΔGf(OH-1 (aq))] - [1ΔGf(CaO (s)) + 1ΔGf(H2O (ℓ))]
[1(-553.54) + 2(-157.28)] - [1(-603.54) + 1(-237.18)] = -27.3799999999999 kJ
-27.38 kJ     (spontaneous)

From ΔG = ΔH - TΔS:
-27.36 kJ     (spontaneous)

## Equilibrium Constant, K (at 298.15 K)

62666.490901
This process is favorable at 25°C.

## Reference(s):

Ebbing, Darrell D. General Chemistry 3rd ed.; Houghton Mifflin Company: Boston, MA, 1990; p 298.