Zn (s) + 2 HCl (aq) → H2 (g) + ZnCl2 (aq)

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Reaction Type:

Single displacement/Oxidation-reduction

Stoichiometry

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 Zn             Mass: g HCl            Mass: g or Solution Volume: mL of Concentration: mol/L H2             Mass: g or Gas Volume: L ZnCl2          Mass: g Heat Released: kJ

Enthalpy of Reaction

[1ΔHf(H2 (g)) + 1ΔHf(ZnCl2 (aq))] - [1ΔHf(Zn (s)) + 2ΔHf(HCl (aq))]
[1(0) + 1(-488.2)] - [1(0) + 2(-167.15)] = -153.9 kJ
-153.90 kJ     (exothermic)

Entropy Change

[1ΔSf(H2 (g)) + 1ΔSf(ZnCl2 (aq))] - [1ΔSf(Zn (s)) + 2ΔSf(HCl (aq))]
[1(130.59) + 1(0.859999999999999)] - [1(41.63) + 2(56.48)] = -23.14 J/K
-23.14 J/K     (decrease in entropy)

Free Energy of Reaction (at 298.15 K)

From ΔGf° values:
[1ΔGf(H2 (g)) + 1ΔGf(ZnCl2 (aq))] - [1ΔGf(Zn (s)) + 2ΔGf(HCl (aq))]
[1(0) + 1(-409.6)] - [1(0) + 2(-131.25)] = -147.1 kJ
-147.10 kJ     (spontaneous)

From ΔG = ΔH - TΔS:
-147.00 kJ     (spontaneous)

Equilibrium Constant, K (at 298.15 K)

5.9188727344e+025
This process is favorable at 25°C.

Reference(s):

Ebbing, Darrell D. General Chemistry 3rd ed.; Houghton Mifflin Company: Boston, MA, 1990; pp 75, 181, 184.
Zumdahl, Steven and Zumdahl, Susan A. Chemistry 9th ed.; Brooks/Cole: Belmont, CA, 2014; p 134.
Atkins, Jones, and Laverman. Chemical Principles 6th ed.; W.H. Freeman and Company: New York, NY, 2013; p F94.