Calculate ΔG° for following reactions using standard values of formation. What is their spontaneity? Are products or reactants favored?

Question

Skin imperfections and uneven discolorations are refined, resurfaced, and smoothed by crystals. Aluminum oxide is used by skin care specialists to alter the skin's surface. Scars, fine lines, wrinkles, and pigment changes brought on by sun exposure are a few examples. Calculate ΔG° for following reactions using standard values of formation. What is their spontaneity? Are products or reactants favored?

4Al(s) + 3O2(g) ⇌ 2Al2O3(s)

 

 

SUBSTANCES	Al(s)	O2(g)	Al2O3(s)
∆S ° (J/mol ● K)	28.3	205.0	50.99
ΔHf ° (kJ/mol)	0	0	-1669.8

Answer 1

4Al(s) + 3O₂(g) ⇌ 2Al₂O₃(s)

∆Gº = ∆Hº - T∆Sº

∆Hº = -1669.8 kJ/mol

∆Sº = 50.99 - (28.3 + 205) = 50.99 - 233.3 = -182.3 J/mol = -0.1823 kJ/mol

∆Gº = -1669.8 - (273)(-0.1823) = -1669.8 + 49.8

∆Gº = -1620 kJ/mol

Because ∆Gº is negative, the reaction is spontaneous and products are favored.