## Mg(OH)2 (s) + 2 HCl (aq) → MgCl2 (aq) + 2 H2O (ℓ)

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## Reaction Type:

Double Displacement

## Stoichiometry

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 Mg(OH)2        Mass: g HCl            Mass: g or Solution Volume: mL of Concentration: mol/L MgCl2          Mass: g H2O            Mass: g Heat Released: kJ

## Enthalpy of Reaction

[1ΔHf(MgCl2 (aq)) + 2ΔHf(H2O (ℓ))] - [1ΔHf(Mg(OH)2 (s)) + 2ΔHf(HCl (aq))]
[1(-801.15) + 2(-285.83)] - [1(-924.66) + 2(-167.15)] = -113.85 kJ
-113.85 kJ     (exothermic)

## Entropy Change

[1ΔSf(MgCl2 (aq)) + 2ΔSf(H2O (ℓ))] - [1ΔSf(Mg(OH)2 (s)) + 2ΔSf(HCl (aq))]
[1(-25.11) + 2(69.91)] - [1(63.18) + 2(56.48)] = -61.43 J/K
-61.43 J/K     (decrease in entropy)

## Free Energy of Reaction (at 298.15 K)

From ΔGf° values:
[1ΔGf(MgCl2 (aq)) + 2ΔGf(H2O (ℓ))] - [1ΔGf(Mg(OH)2 (s)) + 2ΔGf(HCl (aq))]
[1(-717.3) + 2(-237.18)] - [1(-833.87) + 2(-131.25)] = -95.29 kJ
-95.29 kJ     (spontaneous)

From ΔG = ΔH - TΔS:
-95.53 kJ     (spontaneous)

## Equilibrium Constant, K (at 298.15 K)

4.9546690007e+016
This process is favorable at 25°C.

## Reference(s):

Kotz, John C. and Treichel, Paul. Chemistry & Chemical Reactivity 4th ed.; Thomson Brooks/Cole: Belmont, CA, 1999; p 165.