For which process will Δ H° and Δ G° are expected to be most similar?

Question

For which process will Δ H° and Δ G° are expected to be most similar? (A) 2Al(.s.)+Fe2O3(.s.) arrow 2Fe(.s.)+Al2O3(.s.) (B) 2Na(.s.)+2H2O(.l.) arrow 2NaOH(.aq..)+H2(.g.) (C) 2NO2(.g.) arrow N2O4(.g.) (D) 2H2(.g.)+O2(.g.) arrow 2H2O(.g.)

Tardigrade Admin · Accepted Answer

2Al(.s.)+Fe2O3(.s.) arrow 2Fe(.s.)+Al2O3(.s.) As in this reaction all reactants and products are in solid states so in this reaction Δ S° ≈ 0 hence Δ G° ≈ Δ H° . Δ G=Δ H-TΔ S≈ Δ H-0≈ Δ H

Q. For which process will $Δ H^{\circ}$ and $Δ G^{\circ}$ are expected to be most similar?

$2 A l (s) + F e_{2} O_{3} (s) \to 2 F e (s) + A l_{2} O_{3} (s)$

$2 N a (s) + 2 H_{2} O (l) \to 2 N a O H (a q .) + H_{2} (g)$

$2 N O_{2} (g) \to N_{2} O_{4} (g)$

$2 H_{2} (g) + O_{2} (g) \to 2 H_{2} O (g)$

$2 A l (s) + F e_{2} O_{3} (s) \to 2 F e (s) + A l_{2} O_{3} (s)$

As in this reaction all reactants and products are in solid states so in this reaction $Δ S^{\circ} \approx 0$ hence $Δ G^{\circ} \approx Δ H^{\circ}$ .

$Δ G = Δ H - T Δ S \approx Δ H - 0 \approx Δ H$

Q. For which process will ΔH∘ and ΔG∘ are expected to be most similar?

2Al(s)+Fe2​O3​(s)→2Fe(s)+Al2​O3​(s)

2Na(s)+2H2​O(l)→2NaOH(aq.)+H2​(g)

2NO2​(g)→N2​O4​(g)

2H2​(g)+O2​(g)→2H2​O(g)