Based on the standard free energies of formation, which of the following reactions represent a feasible way to synthesize the product?

A. N2 (g) + H2 (g) →N2H4 (g); ΔG∘f=159.3 kJ/mol

B. 2Na (s) + O2 (g) →Na2O2 (s); ΔG∘f=-447.7kJ/mol

C. C (s) + 2S (s) →CS2 (g); ΔG∘f=67.1 kJ/mol

D. Ca (s) + 12O2 (g) →CaO (s); ΔG∘f=-604.0 kJ/mol

According the equation of Gibb's free energy -

∆G = ∆H - T∆S

∆G = is the change in gibb's free energy

∆H = is the change in enthalpy

T = temperature

∆S = is the change in entropy.

And, the sign of the ΔG, determines whether the reaction is Spontaneous or non Spontaneous or at equilibrium,

i. e.,

if

• ΔG < 0, the reaction is Spontaneous

• ΔG > 0, the reaction is non Spontaneous

• ΔG = 0, the reaction is at equilibrium

a.

N₂ (g) + H₂ (g) → N₂H₄ (g); ΔG⁰f = 159.3 kJ/mol

ΔG > 0, the reaction is non Spontaneous, the reaction is not feasible in the forward direction

b.

2Na (s) + O₂ (g) → Na₂O₂ (s); ΔG⁰ f = - 447.7kJ/mol

ΔG < 0, the reaction is Spontaneous, the reaction is feasible in the forward direction.

c.

C (s) + 2S (s) → CS₂ (g); ΔG⁰f = 67.1 kJ/mol

ΔG > 0, the reaction is non Spontaneous, the reaction is not feasible in the forward direction

d.

Ca (s) + 12 O₂ (g) → CaO (s); ΔG⁰f = - 604.0 kJ/mol

ΔG < 0, the reaction is Spontaneous, the reaction is feasible in the forward direction.